Archive
Search

You can search published articles.

Journal Information

Online ISSN
1305-3124

Established
1993

Editors-in-Chief
​Cihat Şen, ​Nicola Volpe

Editors
Cecilia Villain, Daniel Rolnik, M. Mar Gil

Managing Editors
Murat Yayla, Oluş Api

Statistics Editor
Resul Arısoy

Ultrasound in labor: clinical practice guideline by the World Association of Perinatal Medicine (WAPM) and the Perinatal Medicine Foundation (PMF)

Giuseppe Rizzo, Tullio Ghi, Wolfgang Henrich, Boris Tutschek, Kamel RA, Christoph Lees, Ilenia Mappa, Mariya Kovalenko, Wai-lam Lau, Torbjorn Moe Eggebo, Reuven Achiron, Cihat Şen

Article info

Ultrasound in labor: clinical practice guideline by the World Association of Perinatal Medicine (WAPM) and the Perinatal Medicine Foundation (PMF). Perinatal Journal 2022;30(2):- DOI: 10.2399/prn.22.0302002

Author(s) Information

Giuseppe Rizzo1,
Tullio Ghi2,
Wolfgang Henrich3,
Boris Tutschek4,
Kamel RA5,
Christoph Lees6,
Ilenia Mappa7,
Mariya Kovalenko8,
Wai-lam Lau9,
Torbjorn Moe Eggebo10,
Reuven Achiron11,
Cihat Şen12

  1. Università di Roma Tor Vergata, Fondazione Policlinico Tor Vergata , Rome Italy Department of Obstetrics and Gynecology, Rome IT
  2. University of Parma, Parma, Italy -Direttore UOC Ostetricia e Ginecologia Azienda Ospedaliera Universitaria di Parma, Parma Italy -Direttore della Scuola di Specializzazione in Ostetricia e Ginecologia Presidente del CdS Ostetricia, Parma Italy Department of Medicine and Surgery Parma IT
  3. Kliniken für Geburtsmedizin Charité, Campus Virchow Klinikum, Campus Mitte, Berlin, Germany Berlin Germany TR
  4. Facharzt für Gynäkologie und Geburtshilfe FMH, Spezielle Geburtshilfe und feto-maternale Medizin, Zurich, Switzerland Zurich CH
  5. Department of Obstetrics and Gynecology Maternal-Fetal Medicine Unit, Cairo University Cairo EG
  6. Department of Obstetrics, Imperial College London and Fetal Medicine, Imperial College Healthcare NHS Trust., London, UK - Visiting Professor, Department of Development & Regeneration KU Leuven, Belgium London GB
  7. Università di Roma Tor Vergata, Unità Operativa di Medicina Materno Fetale Ospedale Cristo Re Roma, Italy Rome IT
  8. Imperial College Healthcare NHS Trust: London, UK London GB
  9. Department of Obstetrics and Gynecology, Kwong Wah Hospital, Hong Kong SAR, China. Hong Kong CN
  10. National Center for Fetal Medicine, St.Olavs Hospital: Trondheim, Norway Trondheim Norway TR
  11. Department of Obstetrics and Gynecology, Ultrasound unit, Tel-Hashomer, Sackler School of Medicine, Tel-Aviv University, Ramat-Gan, Israel Ramat-Gan IL
  12. Perinatal Medicine Foundation, Istanbul, Turkey and Departmen of Perinatal Medicine, Memorial BAH Hospital, Istanbul, Turkey
Correspondence

Cihat Şen, Perinatal Medicine Foundation, Istanbul, Turkey and Departmen of Perinatal Medicine, Memorial BAH Hospital, Istanbul, Turkey , [email protected]

Publication History

Manuscript Received: March 25, 2022

Manuscript Accepted: March 25, 2022

Earlyview Date: March 25, 2022

Conflicts of Interest

This guideline is published as a parallel publication in the Journal of Perinatal Medicine in aggrement.

This recommendation document follows the mission of the World Association of Perinatal Medicine in collaboration with the Perinatal Medicine Foundation. We aim to bring together groups and individuals throughout the world for precise standardization to implement the ultrasound evaluation in labor and improve the outcome of and the clinical management of the labor. Ultrasound is a safe, reliable, non-invasive tool for assessing bone and soft tissue structures. Women undergo routine ultrasound imaging throughout their pregnancy to estimate fetal weight, locate placental position, liquor volume, and Doppler measurements of feto-placental circulation. It has increasingly become more used in the last decade for improving management in labor by providing more accurate and reproducible findings of progress in labour
Keywords

Ultrasound in labor, obstructed labor, induction of labor, dystocia

Glossary of Terms

U/S – ultrasound
CTG – cardiotocograph
IOL – induction of labor
CL – cervical length
FH – fetal heart
OA – occiput anterior
OP – occiput posterior
OT – occiput transverse
LOT – left occiput transverse
ROT – right occiput transverse
HPD – head to perineum distance
AoP – angle of progression
MLA – midline angle
SPA – maternal subpubic arch angle
PCA – posterior cervical angle
OSA – occiput spine angle
CCA – chin-to-chest angle
  

CONTENT

Section-1: Introduction

Background and rationale for recommendation
Safe machine use and machine cleaning
Method of ultrasound examination  

Section-2: Ultrasound evaluation before labor or upon admission to the labor ward

Excluding low lying placenta
Cervical length (CL) and posterior cervical angle (PCA)
Ultrasound pelvimetry
Assessment of pelvic floor dimensions and function
Fetal presentation and position 

Section 3: Standard intrapartum ultrasound measurements in labor

Heat station
Head station measurement
Head direction
Head perineum distance (HPD)
Angle of Progression (AoP)
Caput succedaneum and Cranial Molding
Fetal head rotation - Midline Angle (MLA)
Flexion/Deflexion
Second Stage of Labor 

Section 4: Ultrasound examination after delivery

Checking the anatomy
Postpartum bleeding
Doppler studies
Pelvic floor after delivery 
 

Section-1: Introduction

 a-Background and rationale for recommendation

 Ultrasound is a safe, reliable, non-invasive tool for assessing bone and soft tissue structures. Women undergo routine ultrasound imaging throughout their pregnancy to estimate fetal weight, locate placental position, liquor volume, and Doppler measurements of feto-placental circulation. It has increasingly become more used in the last decade for improving management in labor by providing more accurate and reproducible findings1-3 of progress in labour. In addition, through evidence-based models, it can be used to predict4-5 mode of delivery. 
 
Fetal descent and position are commonly determined through digital vaginal examinations by the caregiver. This examination method can be painful6,7, associated with ascending infection8 to the fetus and mother, and largely subjective9-10. Intrapartum ultrasound is better tolerated11,12 by women than the traditional method of vaginal examinations and its use has been increasingly researched as an adjunct tool in labor for determination of cervical dilatation, fetal head position and station whilst maintaining sterility. Obstetricians can become competent in basic ultrasound techniques in order to recognise acute clinical emergencies as well as improve the recognition of labor arrest.
 
Intrapartum evaluation of fetal head position, station and flexion plays a key role in the management of labor. Incorrect assessment of these parameters can increase the risk of maternal and perinatal complications.
 
In this guideline, we outline skills of intrapartum ultrasound for Obstetricians. These techniques are not time-consuming and can improve the reliability of clinical examinations in labor. Intrapartum ultrasound should be used to correlate alongside findings of an abdominal palpation and digital vaginal examination.
 
The aim of this examination include; the use of ultrasound evaluation in labor include Identifying singleton or multifetal pregnancy, fetal viability, fetal biometry, amniotic fluid volume, determining factors preventing labor from continuing, low placental location, presentation, ultrasound pelvimetry, fetal occiput and spine position to plan for rotation in the first stage of labor by altering the maternal positioning.
 
For this purpose, the use of ultrasound is easy, simple and making the evaluation in objective way for managing labour in a convenient manner as non-invasive method of either transabdominal and/or transperineal.
 

b-Safe Machine Use and Machine Cleaning

 Ultrasound is a safe tool for imaging fetal and maternal structures throughout pregnancy. Images are produced in real-time using sound waves through a probe (the transducer). Gel is placed directly on the skin as a median to enable sound waves to travel between the object and the probe. Commonly whilst scanning on the labor ward, a low frequency (< 4 MHz) wide-sector convex transducer is used.
 
Probe safe storage: The probe should be stored in the upright vertical position in its slot on the machine, and the cable looped so as to prevent contact with the floor. Ultrasound cables left on the floor are prone to being damaged by footfall or by the wheels of the machine, leading to the unnecessary cost of having to be replaced when inner cables are ruined. Ensure the probe cable does not come into contact with the probe as it is not often disinfected as regularly as the probe. Cross contamination may occur during probe and cable handling.
 
Power cable: The power cable between the ultrasound machine and the power outlet is especially prone to damage. It should have secure connections and the flex should not be damaged.
 
Transperineal ultrasound: Cover the ultrasound probe with a sterile cover or with a sterile examination glove (latex/non-latex). Use sterile gel at the contact point between the cover and the maternal perineum. Once the examination is completed, remove the cover and disinfect the probe according to local protocols. This may be by a chemical method, or ultraviolet disinfection12.
 
Ultrasound gel: Infections have been reported that have led to severe morbidity, traced back to bacterial colonization in gel bottles. Hence, sterile ultrasound gel in single-use containers should be used during ultrasound examinations in labor where invasive procedures such as intrapartum caesarean delivery or instrumental delivery may follow. If single-use containers are not available, to reduce infection rates, the ultrasound gel bottle should not have direct contact with the skin or the probe. It is best practice to place gel on the surface which will be imaged (maternal abdomen) and not on the probe itself.
 

 c-Method of ultrasound examination

 Ultrasound in labor can be performed using a transabdominal or a transperineal approach depending upon which parameters are being assessed. During transabdominal imaging, fetal anatomy, presentation, liquor volume, and placental localization can be determined. The transperineal images depict images of the fetal head in which calculations to determine a proposed fetal head station can be made.
 
Transabdominal
 The maternal position for transabdominal scanning is supine with a left lateral tilt. The transducer is held superior to the symphysis pubis in the positions as depicted in Figure 1 for either transverse or sagittal images.
  
Transperineal
The maternal position is semi-recumbent with legs flexed at the hips. The bladder should be emptied prior to commencement of the scan. The transducer is placed between the labia majora or at the level of the posterior fourchette (Figure 2 and 3). Transperineal ultrasound is a non-invasive technique that has been shown in research to be able to measure head descent13, cervical dilatation14, and used in predictive modelling in mode of birth during labor. Maternal structures visualised during a transperineal ultrasound include symphysis pubis, pelvic floor muscles, bladder and indwelling catheter balloon. The fetal cranium is depicted in relation to the aforementioned maternal structures.
 

Section-2: Ultrasound evaluation before labor or upon admission to the labor ward

Routine ultrasound scanning for pregnant women in labor before admission is considered an integral part of the pre-booking assessment. Moreover, it is of a substantial significance in low resource countries with a high prevalence of walk-ins without antenatal follow up and/or documentation or with very basic antenatal care programs devoid of proper access to U/S machines. In such settings, also, there is an increased likelihood of labor management with no available CTG or other means of fetal surveillance. Proper pre-labor assessment is thus essential to avoid unexpected complications e.g locked twins, fetal anomalies, placenta praevia, malpresentations, impending fetal compromise or intrauterine fetal death.
Ultrasound examination upon admission to labor is indispensable in emergency situations as in cases of antepartum hemorrhage, tetanic uterine contractions to exclude placental abruption, cases of clinical suspicion of rupture uterus or cases of fetal distress requiring Doppler studies.
Induction of labor has become one of the most common interventions in modern obstetrics with a continuously increasing prevalence.14-16
Failure of induction of labor is associated with maternal, fetal and neonatal risks associated with the emergency cesarean deliveries17 and is reported to be as high as 15-20% especially in nulliparous women.18-19
Ultrasound can be employed to help select women who are eligible for induction of labor, and with a reasonable chance success. To determine the eligibility of a woman for IOL, ultrasound can be used for proper gestational age determination, for placental and umbilical cord localization and fetal well-being assessment.18
 

a-Excluding low lying placenta

A low lying placenta refers to a placenta that lies in close proximity to the internal cervical os or covers it. An undiagnosed low lying placenta can have detrimental effects for the mother and the fetus during labor. A transabdominal ultrasound scan in the sagittal view should be used to identify placental location (Figure 4). The placenta can be characterised by identifying the leading edge of the placental membrane in relation to the internal cervical os. Less than 20mm corresponds to a diagnosis of a low-lying placenta.
 

 b-Cervical length (CL) and posterior cervical angle (PCA)

Independent prediction of the induction to delivery interval and the outcome of IOL within 24 hours were possible by CL & PCA measurements.20-21
To measure the cervical length, the curvilinear transducer applied to the perineum to enable simultaneous visualization of the internal and external os and then measured as the distance along a line representing the whole length of the endocervical canal ;22  (Figure 5).
With the same probe applications, the posterior cervical angle is measured as the angle between a line along the cervical canal, in the midsagittal plane and another line tangential to the posterior uterine wall;20 (Figure 6).
Recommendation: The posterior cervical angle provides an accurate measure of the position of the cervix and when the angle is < 120◦ there is prolongation of labor. In women undergoing induction of labor, prediction of outcome can be provided by determining sonographic parameters such as cervical length and posterior cervical angle. Sonographic parameters are superior to the Bishop score in the prediction of the outcome of induction which enables the clinician to provide precise information to plan further management of the pregnancy

c-Ultrasound pelvimetry

Pre-labor transperineal ultrasound assessment of maternal subpubic arch angle (SPA) was able to identify women at high risk of operative vaginal delivery and an association with the persistence of the different occiput positions throughout birth was demonstrated.23,24
SPA is measured as the apex angle between the lines positioned on the pubic rami converging to the center of the symphysis pubis, obtained on an axial view of the outlet;25-26   ( Figure 7).
Another form of ultrasound pelvimetry is to measure the obstetric conjugate. The curvilinear transducer is longitudinally placed at the level of the symphysis to visualize the interpubic fibrocartilaginous disc. The promontory is then identified as the most prominent segment of the sacral vertebral column. The obstetric conjugate is measured as the distance between the inner edge of the interpubic disc sacral promontory[rk1] .25    (Figure 8)
Recommendation: Ultrasound pelvimetry provides the Obstetrician to evaluate the birth canal for managing the labour process safely and appropriately.

d-Assessment of pelvic floor dimensions and function

The levator hiatus can be measured by transperineal ultrasound on the mid-sagittal view as the distance between the inferior border of the symphysis pubis to the anterior border of the puborectalis muscle (Figure 9 )
A correlation between pelvic floor dimension and labor outcome, mainly the duration of the second stage of labor was reported. Comparing the levator hiatal dimensions of a woman at rest to that at Valsalva allows the identification of women with levator ani co-activation with the potential of visual feedback and coaching to correct the co-activation.26,27

 e- Fetal presentation and position

It is well established in the literature that clinical examination using abdominal palpation has low sensitivity for determining malpresentations28. Transabdominal ultrasound scanning in the sagittal plane is used to identify the fetal presentation29. The transducer should be placed in the midline of the maternal abdomen, at the level of the symphysis pubis. In this view, structures visualized include the maternal bladder, lower uterine segment and the internal cervical os. This allows correct visualization of the fetal presenting part by determining its relationship to the cervix and the placenta. Fetal presentation should be assessed in conjunction with fetal lie - longitudinal assessment in relation to the maternal long axis.
 
The fetal head position is defined as the orientation of the presenting fetal head within the maternal pelvic inlet30. The relationship of the fetal occiput to the fetal head can be further described31.
 
During a digital vaginal examination in labor, the fetal position is determined by palpation of the cranial suture lines as well as the anterior and posterior fontanels. Inaccuracies exist in this method for the diagnosis of fetal position as the examination is subjective and increases in difficulty during the presence of caput succedaneum in prolonged labor32. Determining fetal position has shown to be more prone to error in non-occipital anterior positions2.
 
Intrapartum ultrasound is an improved method for determining fetal head position33. The assessment of the woman by ultrasound has been recommended to be routinely used prior to commencing an assisted vaginal delivery and where there is clinical uncertainty about the fetal position34-35. A transabdominal or transperineal sonographic approach can be used according to the degree of engagement of the fetal head. In the transabdominal scan, place the transducer in the suprapubic region (Figure 1). The landmarks to evaluate for fetal position are shown in Figure 10 , Figure 11, Figure 12 and Figure 13.
 
If the fetal head is deeply engaged in the maternal pelvis, the midline structures can be difficult to through a transabdominal scan. A transperineal scan (Figure 2A) can also be performed to obtain images of the fetal position easily and effectively.
 
A systematic approach to defining fetal position is used amongst Obstetricians. The location of the fetal spine and occiput are used as anatomic landmarks and related to a clock face. Occiput anterior position is situated between 10 and 2 o’clock; occiput posterior position if situated between 4 and 8 o’clock; occiput transverse position if situated between 2 and 4 o’clock (left occiput transverse – LOT), or between 8 and 10 o’clock (right occiput transverse – ROT). Figure 10 outlines this relationship and the classification.

By placing the ultrasound transducer transversely on the maternal abdomen, you can obtain axial views of the fetal trunk. The level of the fetal upper abdomen or thorax can be used to locate the position of fetal vertebrae (Figure 11). The spine position can then be related to a clock face in the same classification as depicted in Figure 10.
It is clinically advantageous to assess the fetal position by performing ultrasound of the fetal head as well as the fetal torso to unequivocally appreciate the fetal descent and rotation throughout labor (Figure 12 and Figure 13). Malpositions are associated with prolonged labor and increased intervention rates, therefore accurate monitoring of progress in labor is beneficial for achieving good fetal and maternal outcomes.

Recommendation: Ultrasound evaluation before induction or just before labour gives you an opportunity to evaluate and understand the condition of the baby and the birth canal. Therefore you can manage the case at optimum condition and not to have any surprise that puts you and your patient on a difficult position and results.
  

Section-3 – Standard Intrapartum Ultrasound Measurements in Labor

 Intrapartum ultrasound with the transperineal approach enables detailed visualization of fetal and maternal structures in labor that can be challenging to identify through transabdominal scanning.
 

a-Fetal head station

Fetal head station is the most important marker of descent which requires identification of the head in relation to the maternal ischial spines in centimetres. On digital vaginal examination, if the deepest bony part is at the level of the ischial spines, this station is defined as 0 cm. It is determined by placing fingers on the cranium and the ischial spines for a subjective interpretation of the level corresponding to nominal intervals above or below the maternal spine35-38.
 
The advantage of transperineal ultrasound examination, on the other hand, is a precise and reproducible assessment of fetal head station39. For the transperineal ultrasound examination, the probe is placed between the two labia majora or at the level of the fourchette, with the legs flexed at the hips and knees. In the median plane the two main anatomical landmarks can be seen as  pubic symphysis joint and the fetal skull (see Figure 14).
At ultrasound, the ischial spine is not visible, in this median infrapubic view, several parameters for the head station have been proposed that use the pubic symphysis as a reference for quantitative measurements by transperineal ultrasound: Measurement of the head station, the head direction, the head-perineum distance (HPD) and the angle of progression (AoP) have been used to correlate to the fetal head descent (40-41) which indicate head station indirectly. Predictive modelling for mode of birth has been proposed by utilising transperineal ultrasound measurements, however all information regarding fetal position and head station should be considered during an assessment (42).

a1-Measurement of the head station

At ultrasound examination, the ischial spine is not visible but indirectly can be estimated which is 3 cm below to the perpendicular line to the lower margin of the pubic bone, which is a fixed anatomical relationship) (39) (Figure 14). Therefore the measurement of the head station is a method of measurement such as the relation of the deepest bony part of the fetal head to the perpendicular line to the lower margin of the pubic bone minus 3cm. This method is a objective evaluation of the head station but a little bit time consuming.

a2- Head direction

It is indicated indirectly but more easy and quick method to evaluate the head station. The head direction is head down in case of the wider diameter of the head above the ischial spines, head horizontal in case of the wider diameter of the head at the ischial spines,  and head up in case of the wider diameter of the head above the ischial spines, head horizontal in case of the wider diameter of the head below the ischial spines.
The head direction (head down, head horizontal or head up) indicates the direction of the longest recognizable axis of the fetal head with respect to the long axis of the pubic symphysis (39). It is particularly useful for a quick assessment as an upwards head direction ("head up sign") indicates a favorable station before operative vaginal delivery (Figure 14).

a3-Head-perineum distance (HPD)

The head–perineum distance (HPD) is measured using transperineal ultrasound with the transducer placed transversely between the labia majora (Figure 2A). The soft tissue should be compressed completely against the pubic bone during the scan. The transducer should be angled until the fetal skull contour is as clear as possible40,43, indicating that the ultrasound beam is perpendicular to the fetal skull (Figure 15-A). A measurement is taken in the midline from the transducer to the leading edge of the fetal cranium (Figure 15-B). The resulting measurement (HPD) is the shortest distance between the perineum (the transducer) and the outer bony limit of the fetal skull. Although the distance represents the part of the birth canal yet to be passed by the fetus, it is measuring a straight line and does not take the pelvic curve into consideration44. Taking this into consideration, studies by Tutschek et al.36 found head station at zero corresponded to a HPD measurement of 36 mm and Kahrs et al.45 found head station at zero corresponded to a HPD of 35 mm. These can be considered when relating HPD with fetal head descent.
 
 The advantages of hear perineum distance for the clinicians are that is fast to obtain and easy to measure resulting particularly useful in emergency situation such as before an operative vaginal delivery. The major limitation is the difficulty of standardize the operator pressure in maternal soft tissue

 a4-Angle of progression (AoP)

The angle of progression (AoP) is the angle between the long axis of the pubic bone and a line from the lowest edge of the pubis drawn tangential to the deepest bony part of the fetal skull45. The angle of progression is measured using a transperineal ultrasound approach in mid-sagittal scan (Figure 2B) and the method for obtaining measurements is described in Figure 16. The anatomic landmarks visualized during this scan include the pubic symphysis bone, as an oblong, irregular, echogenic structure (ideally displayed in a horizontal position) and the fetal skull (Figure 17). The angle enlarges with the progressive descent of the fetal head in the birth canal, and therefore originally was called angle of head descent. Numerous studies,46-49 have correlated AoP between 110 and 120 degrees to the digital assessment equivalent of the level of ischial spines (zero).
 
The advantage of the angle of progression for the clinicians is to provide a reliable assessment of head station. The limitation is that a proper visualization of the pubic bones is required.
 
Recommendation: Regarding the head station, head direction (such as head-up sign) or head-perineum distance easy, quick way to evaluate or may be better take the measurement the angle of progression. 

b-Caput succedaneum and Cranial Molding

 The presence of caput (a soft tissue swelling) and molding (overlapping of fetal cranial bones) in labor contributes to the difficulty in assessment of fetal head position and station. An objective visual method for describing its presence can be portrayed with transperineal ultrasound in a sagittal plane (Figure 18). The presence of these factors may influence an Obstetrician’s decision when considering an operative vaginal birth.
 
Recommendation: The advantage of this examination gives an opportunity to the clinician not to take wrong impression about the head station. 

c-Fetal Head Rotation - Midline Angle (MLA)

The midline angle specifically describes fetal head rotation, as opposed to descent, as a marker of progress in labor. The measurement is obtained using transperineal ultrasound in the transverse plane. The midline of the fetal head is identified and a linear marker is set at this point for reference. An angle is taken between the fetal midline structures and the anteroposterior axis of the maternal pelvis (Figure 19). A clinical significance is present between head station and fetal head rotation39.
Further parameters to represent head descent in the maternal pelvis can be measured including midline-angle (MLA). The advantage of this method is to understand the progress of the head in the pelvis objectively because the digital examination is not giving a reliable method of establishing the progress and head descent.
 
Recommendation: If you want to evaluate the head rotation in the birth canal, take the measurement of midline angle which gives you an opportunity to manage the labour objectively. 

d- Flexion/Deflexion

The fetal head flexion facilitates the engagement and the progression of fetal head in the birth canal, exposing the suboccipito-bregmatic diameter, that is shorter than the occipito-frontal diameter. Even though fetal head hyperextension is a common cause of dystocia, clinical diagnosis is difficult and imprecise, therefore the exact prevalence of this condition is unknown. The fetal head flexion can be quantitively defined by the occiput-spine angle (OSA) for fetuses with occiput anterior and transverse position and by the chin-to-chest angle (CCA) for the fetuses with occiput posterior position50-53. In the incidence of vaginal deliveries, a wide OSA and a narrow CCA are seen54.
 
Recommendation: In cases of suspected dystocia (such as deflexion abnormalities) , take the measurement for occiput-spine angle or chin-to-chest angle. Therefore the advantage of this examination is to make better and objective clinical decision to predict the dystocia for proper management.
  
Occiput-spine-angle (OSA) - Flexion/Deflexion: The occiput-spine angle (OSA) corresponds to the angle between a line drawn tangential to the cervical spine and a second line drawn tangential to the occiput (Figures 20-22). This represents the degree of head flexion in the maternal pelvis in an occipital anterior or occipital transverse fetal head position. Through quantifying the relationship between the fetal occiput and the spine, the Obstetrician can evaluate normal process of labor and detect early signs of obstruction49. In the presence of fetal head deflexion, the outcome of a cesarean delivery is increased52.
 
Chin-to-chest angle (CCA) – Flexion/Deflexion: The chin-to-chest angle (CCA) is defined as the angle between the intersection of a line passing by the long axis of the sternum and a second line drawn tangential to the skin that covers the inferior limit of oral cavity up to the chin (Figures 23-25). In the occiput posterior fetal position, this is an alternative measure to OSA to describe fetal head flexion.

e- The Second Stage

According to the World Health Organization (WHO), the definition of second stage labor is the interval between the initiation of full cervical dilatation and birth of the baby. Adverse outcomes for both the mother and her baby have been associated with a prolonged duration in second stage of labour as well as higher likelihood of requiring an assisted birth54-56. The recommended duration of this stage in labour still remains debated worldwide. An Obstetrician assesses the cause of the delay in labour and may propose an operative vaginal delivery (vacuum, forceps or caesarean section).
A study of prolonged labour in 150 women, measured transperineal ultrasound distance of HPD ≤40mm and the AoP≥110° corresponded to an outcome of a spontaneous vaginal delivery in 92% and 88% of women respectively which demonstrates promising data on the utility of these values for prediction of type of birth57.
Transperineal measurement of HPD both during at rest and during active second stage was able to quantify fetal head descent and thus illustrate that minimal descent was associated with longer duration of second stage and higher chance of CS58. Furthermore, a recent systematic review supports ultrasound prediction in labour by demonstrating an AoP between 108-119° at the beginning of second stage of labour was associated with a successful vaginal birth59.
During second stage, a proposed algorithm model using the concept of a “traffic light” by incorporating both clinical and sonographic parameters is useful to consider60-62. It may guide clinicians on their decision on the choice of assisted vaginal delivery and alert junior Obstetricians to consider senior assistance prior to commencing delivery. Asynclitism is often underdiagnosed. It could be as common as 15% in second stage of labor amongst nulliparous women. A simple rule for diagnosis is that the midline echo could not be seen easily at the head-perineum distance plane63. Obstetricians should be aware of this condition, especially when encountering fetuses in non-OA position before attempting instrumental deliveries.

Recommendation: Intrapartum ultrasound can be used during all stages of pre-labor and labor for diagnosis of malpositions and understand underlying mechanisms of labor arrest. In this manner, ultrasound alongside clinical findings, can improve clinical care. Through evaluation of fetal position, station and rotation, the Obstetrician can oversee labor progress and make objective judgements over intended clinical interventions.
 

Section 4: Ultrasound examination after delivery

Checking the anatomyApplications of postpartum sonography (Figure 26 and 27) include the exclusion of placental remnants immediately after birth in the context of postpartum hemorrhage, the possible need for ultrasound-guided curettage and the exclusion of uterine rupture in vaginal birth after previous cesarean section. After primary cesarean section without opening of the cervix lochial stasis can lead to lower abdominal pain and in these cases a significant intrauterine blood collection can be detected on ultrasound. Sonography is also used for the diagnosis of intra-abdominal or abdominal wall hematomas, and other rare causes of persistent or acute postpartum bleeding such as placental polyps, arteriovenous malformations and pseudo-aneurysms.  64,65. 
Postpartum bleedingIn postpartum bleeding, immediate sonography helps to distinguish between uterine atony and bleeding caused by tissue (placental retention) or trauma.
In placental retention, the placenta is not born within 30 to 60 minutes. It is the second most common cause of postpartum hemorrhage (PPH) after uterine atony. A completely or partially separated retained placenta impairs uterine contraction and often leads to increased bleeding. In such cases, the placenta must be separated manually or removed instrumentally, preferably under ultrasound guidance. The sonographic surveillance during such procedures reduces the risk of complications, for example uterine perforation or the incomplete emptying of remnants.
After manual or instrumental removal of the placenta or placental remnants, the sonographically empty cavity of the uterus can be imaged and documented (Figure 28).

In the case of uterine atony resistant to uterotonics, which often occurs after manual and instrumental emptying of the cavity, the insertion of an intrauterine chitosan tamponade or of a balloon (Bakri balloon) has proven to be effective (Figure 29). The correct position of the tamponade or balloon can be confirmed sonographically. The secondary accumulation of blood in the uterine cavity can also be detected.

Postpartum and post-operatively, abdominal sonography is also helpful to detect hematomas and to determine their size Figure 30): they can be separate from the uterus, for example in the case of a uterine rupture. In the case of persistent postoperative vaginal bleeding after curettage, free abdominal fluid or a localized hematoma can be detected next to the rupture site in the abdomen, and the volume of blood loss can be better estimated and correlated with circulatory parameters and hemoglobin levels. 66,67.

Uterine compression sutures are used as an alternative to a tamponade in cases of therapy-resistant bleeding during a cesarean68,69. These sutures can be visualized by ultrasound and followed up in the postoperative course weeks later. 
c-Doppler studiesBoth B-scan imaging and color Doppler sonography of the placenta can help to detect a pathological placental period. The absence of placenta separation signs and the persistence of blood flow between the myometrium and placenta in color Doppler may be an indication of abnormally invasive placenta (AIP), such as placenta accreta, increta or percreta (Figure 31). In some cases, the patient may benefit from ultrasound-guided curettage to selectively remove cotyledons implanted at a deeper focal point, and in other cases, to act cautiously in the case of AIP with a very thin myometrium and the danger of perforation. At the end of the procedure, an ultrasound image can be used to document the successful performance of the  intervention and confirm the empty cavity.

The detection of perfusion, using color Doppler, in an intracavitary mass is diagnostic of placental remnants 70. Cotyledons cannot always be distinguished from organized blood clots  or a submucous myoma by the B-mode image alone. Increased blood flow to the myometrium in the area of the adherent placental residue is typical, but absent in blood clots and in older or detached non-perfused  placental remnants. Increased vaginal bleeding after a caesarean section in the puerperium can also indicate placental remnants.

Arterio-venous malformations (AVM) are a rare differential diagnoses of pathological postpartum uterine bleeding71. They occur after uterine trauma (surgery) or are, rarely, congenital; they may occasionally become symptomatic postpartum for the first time. In B-Mode Ultrasound a cystic mass in the myometrium is visible and color Doppler sonography reveals a dense vascular mass in the myometrium with turbulent flow typical of uterine AVM. Correctly diagnosing a symptomatic AVM is essential to avoid the accidental provocation of increased bleeding during an attempted curettage Figure 32).
 
Pelvic floor after deliveryPerineal sonography can be used to assess the pelvic floor and sphincter anatomy. Internal and external sphincters and the levator ani can be examined not only statically but also dynamically (when the pelvic floor is tensed and relaxed). Sonographically it appears as a local interruption of continuity of the soft tissue mantle or vaginal sidewall. This new application of postpartum sonography is increasingly being used for the early diagnosis of occult or clinically significant pelvic floor and sphincter damage. Reference
Recommendation: In a case of any suspected postpartum pathology, the us of ultrasound examination is always to keep you safe and to give you better management of postpartum period.

References

1.Dupuis O, Ruimark S, Corrine D, Simone T, Andre D, Rene- Charles R. Fetal head position during the second stage of labor: comparison of digital and vaginal examination and transabdominal ultrasonographic examination. Eur J Obstet Gynecol Reprod Biol 2005; 123:193–197.
2.Akmal S, Kametas N, Tsoi E, Hargreaves C, Nicolaides KH. Comparison of transvaginal digital examination with intrapartum sonography to determine fetal head position before instrumental delivery. Ultrasound Obstet Gynecol 2003; 21: 437–440.
3.Sherer DM, Miodovnik M, Bradley S, Langer O. Intrapartum fetal head position I: comparison between transvaginal digital examination and transabdominal ultrasound assessment during the active stage of labor. Ultrasound Obstet Gynecol 2002;19: 258–263.
4.Sainz JA, Borrero C, Aquise A, Serrano R, Gutierrez L, Fern ´ andez-Palac ´ ´ın A. Utility of intrapartum transperineal ultrasound to predict cases of failure in vacuum extraction attempt and need of cesarean section to complete delivery. J Matern Fetal Neonatal Med 2016; 29: 1348–1352.
5.Kasbaoui S, Severac F, A ´ ¨ıssi G, Gaudineau A, Lecointre L, Akladios C, Favre R, Langer B, Sananes N. Predicting the difficulty of operative vaginal delivery by ultrasound measurement of fetal head station. Am J Obstet Gynecol 2017; 216:507.e1–9
6.Usman S, Barton H, Wilhelm-Benartzi C, Lees CC. Ultrasound is better tolerated than vaginal examination in and before labour. Aust N Z J Obstet Gynaecol. 2019;59(3):362-366
7. Rizzo G, Aloisio F, Bacigalupi A, Mappa I, Słodki M, Makatsarya A, D'Antonio F. Women's compliance with ultrasound in labor: a prospective observational study. J Matern Fetal Neonatal Med. 2021;34(9):1454-1458
8.Westover T, Knuppel RA. Modern management of clinical chorioamnionitis. Infect Dis Obstet Gynecol. 1995;3(3):123–132
9.Buchmann EJ, Libhaber E. Accuracy of cervical assessment in the active phase of labour. BJOG: An International Journal of Obstetrics & Gynaecology. 2007;114(7):833–837
10. Dupuis O, Silveira R, Zentner A, Dittmar A, Gaucherand P, Cucherat M, Redarce T, Rudigoz R-C. Birth simulator: reliability of transvaginal assessment of fetal head station as defined by the American College of Obstetricians and Gynecologists classification. Am J Obstet Gynecol. 2005;192(3):868–874
11. Cuerva MJ, García-Casarrubios P, García-Calvo L, Gutiérrez-Simon M, Ordás,Fernando P,
Bartha MJL, ITU-R12 Group . Use of intrapartum ultrasound in term pregnant women with contractions before hospital admission. Acta Obstet Gynecol Scand. 2019;98(2):162-166
12. Abramowicz JS, Basseal JM, Brezinka C, Dall'Asta A, Deng J, Harrison G, Lee JCS, Lim A, Maršal K, Miloro P, Poon LC, Salvesen KÅ, Sande R, Ter Haar G, Westerway SC, Xie MX, Lees C. ISUOG Safety Committee Position Statement on use of personal protective equipment and hazard mitigation in relation to SARS-CoV-2 for practitioners undertaking obstetric and gynecological ultrasound. Ultrasound Obstet Gynecol. 2020;55(6):886-891
13. Usman S, Wilkinson M, Barton H, Lees CC. The feasibility and accuracy of ultrasound assessment in the labor room. J Matern Fetal Neonatal Med. Oct 2019;32(20):3442-3451
14. Verhoeven CJM, Oudenaarden A, Hermus MAA, Porath MM, Oei SG, Mol BWJ. Validation of models that predict Cesarean section after induction of labor. Ultrasound Obstet Gynecol. 2009;34(3):316-321
15. Banõs N, Migliorelli F, Posadas E, Ferreri J, Palacio M. Definition of Failed Induction of Labor and Its Predictive Factors: Two Unsolved Issues of an Everyday Clinical Situation. Fetal Diagn Ther. 2015;38(3):161-169
16. ACOG practice bulletin no. 107: Induction of labor. Obstet Gynecol. 2009;114(2 PART 1):386-397
17. Hannah ME. Planned elective cesarean section: A reasonable choice for some women? Cmaj. 2004;170(5):813-814
18.NICE. Induction of Labour. National Collaborating Centre for Women’s and Children’s Health Commissioned. National Institute for Health and Care Excellence. 2008
19. Crowley P. Interventions for preventing or improving the outcome of delivery at or beyond term. Cochrane Database Syst Rev. 2006
20. Rane SM, Guirgis RR, Higgins B, Nicolaides KH. Pre-induction sonographic measurement of cervical length in prolonged pregnancy: The effect of parity in the prediction of the need for Cesarean section. Ultrasound Obstet Gynecol. 2003;22(1):45-48
21. Rane SM, Guirgis RR, Higgins B, Nicolaides KH. The value of ultrasound in the prediction of successful induction of labor. Ultrasound Obstet Gynecol. 2004;24(5):538-549
22. Kagan KO, Sonek J. How to measure cervical length. Ultrasound Obstet Gynecol. 2015;45(3):358- 362
23. Ghi T, Youssef A, Martelli F, Bellussi F, Aiello E, Pilu G, Rizzo N, Frusca T, Arduini D, Rizzo G. Narrow subpubic arch angle is associated with higher risk of persistent occiput posterior position at delivery. Ultrasound Obstet Gynecol. 2016;48(4):511-515
24. Gilboa Y, Kivilevitch Z, Spira M, Kedem A, Katorza E, Moran O, Achiron R. Pubic arch angle in prolonged second stage of labor: clinical significance. Ultrasound Obstet Gynecol. 2013;41(4):442-446
25. Di Pasquo E, Volpe N, Labadini C, et al. Antepartum evaluation of the obstetric conjugate at transabdominal 2D ultrasound: A feasibility study. Acta Obstet Gynecol Scand. 2021;100:1917– 1923
26. Kamel R, Montaguti E, Nicolaides KH, et al. Contraction of the levator ani muscle during Valsalva maneuver (coactivation) is associated with a longer active second stage of labor in nulliparous women undergoing induction of labor. Am J Obstet Gynecol. 2019;220(2):189.e1-189.e8
27. Youssef A, Montaguti E, Dodaro MG, Kamel R, Rizzo N, Pilu G. Levator ani muscle coactivation at term is associated with longer second stage of labor in nulliparous women. Ultrasound Obstet Gynecol. 2019;53(5):686-692
28. Nassar N, Roberts CL, Cameron CA, Olive EC. Diagnostic accuracy of clinical examination for detection of non-cephalic presentation in late pregnancy: cross sectional analytic study. BMJ. 2006;;333(7568):578-80
29. Bellussi F, Ghi T, Youssef A, Salsi G, Giorgetta F, Parma D, Simonazzi G, Pilu G. The use of intrapartum ultrasound to diagnose malpositions and cephalic malpresentations. Am J Obstet Gynecol. 2017;217(6):633-641
30. Blasi I, D’Amico R, Fenu V, Volpe A, Fuchs I, Henrich W, Mazza V. Sonographic assessment of fetal spine and head position during the first and second stages of labor for the diagnosis of persistent occiput posterior position: a pilot study. Ultrasound Obstet Gynecol 2010; 35:210–215.
31. Youssef A, Ghi T, Pilu G. How to perform ultrasound in labor: Assessment of fetal occiput position. Ultrasound Obstet Gynecol. 2013;41(4):476-478
32. Ramphul M, Kennelly M, Murphy DJ. Establishing the accuracy and acceptability of abdominal ultrasound to define the foetal head position in the second stage of labour: a validation study. Eur J Obstet Gynecol Reprod Biol 2012; 164: 35–39.
33. Ramphul M, Ooi PV, Burke G, Kennelly MM, Said SA, Montgomery AA, Murphy DJ. Instrumental delivery and ultrasound: a multicentre randomised controlled trial of ultrasound assessment of the fetal head position versus standard care as an approach to prevent morbidity at instrumental delivery. BJOG 2014; 121: 1029–1038.
34. Ghi, T., Eggebø, T., Lees, C., Kalache, K., Rozenberg, P., Youssef, A., Salomon, L.J. and Tutschek, B. ISUOG Practice Guidelines: intrapartum ultrasound. Ultrasound Obstet Gynecol, 2018;52: 128-139
35. Bellussi F, Di Mascio D, Salsi G, Ghi T, Dall’Asta A, Zullo F, Pilu G, Barros JG, Ayres-de-Campos D, Berghella V. Sonographic knowledge of occiput position to decrease failed operative vaginal delivery: a systematic review and meta-analysis of randomized controlled trials. Am J Obstet Gynecol. 2021:S0002-9378(21)00994-7
36. Tutschek B, Torkildsen EA, Eggebo TM. Comparison between ultrasound parameters and clinical examination to assess fetal head station in labor. Ultrasound Obstet Gynecol 2013;41: 425–429
37. Dietz HP, Lanzarone V. Measuring engagement of the fetal head: validity and reproducibility of a new ultrasound technique. Ultrasound Obstet Gynecol 2005; 25: 165–168. 31.
38. Buchmann E, Libhaber E. Interobserver agreement in intrapartum estimation of fetal head station. Int J Gynaecol Obstet. 2008;101(3):285-9
39. Molina, FS, Terra R, Carrillo MP, Puertas A, Nicolaides KH. What is the most reliable ultrasound parameter for assessment of fetal head descent? 2010;36:493-499
40. Eggebø TM, Gjessing LK, Heien C, Smedvig E, Økland I, Romundstad P, Salvesen KA. Prediction of labor and delivery by transperineal ultrasound in pregnancies with prelabor rupture of membranes at term. Ultrasound Obstet Gynecol. 2006;27(4):387-91
41. Dückelmann AM, Bamberg C, Michaelis SA, Lange J, Nonnenmacher A, Dudenhausen JW, Kalache KD. Measurement of fetal head descent using the 'angle of progression' on transperineal ultrasound imaging is reliable regardless of fetal head station or ultrasound expertise. Ultrasound Obstet Gynecol. 2010;35(2):216-22
42. Eggebø TM, Hjartardottir H. Descent of the presenting part assessed with ultrasound. Am J Obstet Gynecol. 2021:S0002-9378(21)00964-9
43. Torkildsen EA, Salvesen KÅ, Eggebaø TM. Prediction of delivery mode with transperineal ultrasound in women with prolonged first stage of labor. Ultrasound Obstet Gynecol. 2011;37(6):702-708
44. Eggebø TM, Heien C, Økland I, Gjessing LK, Romundstad P, Salvesen KÅ. Ultrasound assessment of fetal head-perineum distance before induction of labor. Ultrasound Obstet Gynecol. 2008;32(2):199-204
45. Kahrs BH, Usman S, Ghi T, Youssef A, Torkildsen EA, Lindtjørn E, Østborg TB, Benediktsdottir S, Brooks L, Harmsen L, Romundstad PR, Salvesen KA, Lees CC, ˚Eggebø TM. Sonographic prediction of outcome of vacuum deliveries: a multicenter, prospective cohort study. Am J Obstet Gynecol 2017; 217: 69.e1–10
46. Rizzo G, Mattioli C, Mappa I, Bitsadze V, Khizroeva J, Makatsariya A, D'Antonio F. Antepartum ultrasound prediction of failed vacuum-assisted operative delivery: a prospective cohort study. J Matern Fetal Neonatal Med. 2021;20):3323-3329
47. Barbera AF, Pombar X, Peruginoj G, Lezotte DC, Hobbins JC. A new method to assess fetal head descent in labor with transperineal ultrasound. Ultrasound Obstet Gynecol. 2009;33(3):313-319
48. Arthuis CJ, Perrotin F, Patat F, Brunereau L, Simon EG. Computed tomographic study of anatomical relationship between pubic symphysis and ischial spines to improve interpretation of intrapartum translabial ultrasound. Ultrasound Obstet Gynecol. 2016 Dec;48(6):779-785
49. Bamberg C, Scheuermann S, Slowinski T, Dückelmann AM, Vogt M, Nguyen-Dobinsky TN, Streitparth F, Teichgräber U, Henrich W, Dudenhausen JW, Kalache KD. Relationship between fetal head station established using an open magnetic resonance imaging scanner and the angle of progression determined by transperineal ultrasound. Ultrasound Obstet Gynecol. 2011 Jun;37(6):712-6
50. Ghi T, Bellussi F, Azzarone C, Krsmanovic J, Franchi L, Youssef A, Lenzi J, Fantini MP, Frusca T, Pilu G. The ‘‘occiput-spine angle’’: a new sonographic index of fetal head deflexion during the first stage of labor. Am J Obstet Gynecol 2016; 215: 84.e1–7
51. Ghi T, Bellussi F, Pilu G. Sonographic diagnosis of lateral asynclitism: a new subtype of fetal head malposition as a main determinant of early labor arrest. Ultrasound Obstet Gynecol 2015; 45: 229–231.
52. Gamal Abd El-Nasser, N., Mohamed Abd El-Azem Mira, I., Abd El-Hamed Sedek, A. Measurement of fetal occiput-spine angle during the first stage of labor in primigravida as a predictor of the mode of labor. Al-Azhar Medical Journal, 2021; 50(4): 2655-2666. doi: 10.21608/amj.2021.196407
53. Bellussi F, Livi A, Cataneo I, Salsi G, Lenzi J, Pilu J. Sonographic diagnosis of fetal head deflexion and the risk of cesarean delivery. Am J Obstet Gynecol MFM 2020;2:100217.
54. Dall'Asta A, Rizzo G, Masturzo B, Di Pasquo E, Schera GBL, Morganelli G, Ramirez Zegarra R, Maqina P, Mappa I, Parpinel G, Attini R, Roletti E, Menato G, Frusca T, Ghi T. Intrapartum sonographic assessment of the fetal head flexion in protracted active phase of labor and association with labor outcome: a multicenter, prospective study. Am J Obstet Gynecol. 2021;225(2):171.e1-171.e12.
55. Allen VM, Baskett TF, O'Connell CM, McKeen D, Allen AC. Maternal and perinatal outcomes with increasing duration of the second stage of labor. Obstet Gynecol. 2009;113(6):1248-1258
56. Grobman WA, Bailit J, Lai Y, Reddy UM, Wapner RJ. Association of the Duration of Active Pushing With Obstetric Outcomes. Obstet Gynecol. 2016;127(4):667-673
57. Fraser WD, Marcoux S, Krauss I, Douglas J, Goulet C, Boulvain M. Multicenter, randomized, controlled trial of delayed pushing for nulliparous women in the second stage of labor with continuous epidural analgesia. The PEOPLE (Pushing Early or Pushing Late with Epidural) Study Group. Am J Obstet Gynecol. 2000;182(5):1165-72
58. Eggebø TM, Hassan WA, Salvesen K, Lindtjørn E, Lees CC. Sonographic prediction of vaginal delivery in prolonged labor: a two-center study. Ultrasound Obstet Gynecol. 2014;43(2):195-201
59. Kahrs BH, Usman S, T, Ghi T, Youssef A, Torkildsen EA, Lindtjørn E, et al. Descent of fetal head during active pushing: secondary analysis of prospective cohort study investigating ultrasound examination before operative vaginal delivery. Ultrasound Obstet Gynecol.  2019;54(4):524-529
60. Nassr A, Berghella V, Hessami K, Bibbo C, Bellussi F, Robinson JN et al. Intrapartum ultrasound measurement of angle of progression at the onset of the second stage of labor for prediction of spontaneous vaginal delivery in term singleton pregnancies: a systematic review and meta-analysis. Am J Obstet Gynecol. 2021;S0002-9378(21)00874-7
61. Chan VYT, Lau WL. Intrapartum ultrasound and the choice between assisted vaginal and cesarean delivery. Am J Obstet Gynecol MFM. 2021;3(6) Supp:100439.
62. Mappa I, Tartaglia S, Maqina P, Makatsariya A, Ghi T, Rizzo G, D'Antonio F. Ultrasound vs routine care before instrumental vaginal delivery: A systematic review and meta-analysis. Acta Obstet Gynecol Scand. 2021;100(11):1941-1948
63. Hung CMW, Chan VYT, Ghi T, Lau WL. Asynclitism in the second stage of labor: prevalence, associations, and outcome. Am J Obstet Gynecol MFM. 2021;1;3(5):100437
64. Koskas M, Nizard J, Salomon LJ, Ville Y. Abdominal and pelvic ultrasound findings within 24 hours following uneventful Cesarean section. Ultrasound Obstet Gynecol. 2008;32(4):520-6
65. Sokol ER, Casele H, Haney EI. Ultrasound examination of the postpartum uterus: what is normal? J Matern Fetal Neonatal Med. 2004;15(2):95-9
66. Deans R, Dietz HP. Ultrasound of the post-partum uterus. Aust N Z J Obstet Gynaecol. 2006;46(4):345-9
67. Neill AC, Nixon RM, Thornton S. A comparison of clinical assessment with ultrasound in the management of secondary postpartum haemorrhage. Eur J Obstet Gynecol Reprod Biol. 2002;104(2):113-5
68. Cho Y, Rizvi C, Uppal T, Condous G. Ultrasonographic visualization of balloon placement for uterine tamponade in massive primary postpartum hemorrhage. Ultrasound Obstet Gynecol. 2008;32(5):711-3
69. Kondoh E, Konishi M, Kariya Y, Konishi I. Ultrasonographic visualization of bleeding sites can help control postpartum hemorrhage using intrauterine balloon tamponade. J Clin Ultrasound. 2015;43(1):23-5
70. Steinkeler J, Coldwell B, Warner MA.  Ultrasound of the Postpartum Uterus, Ultrasound Quarterly. 2012;28(2):97-103
71. Pohlan J, Hinkson L, Wickmann U, Henrich W, Althoff CE. Pseudo aneurysm of the uterine artery with arteriovenous fistula after cesarean section: A rare but sinister cause of delayed postpartum hemorrhage. J Clin Ultrasound. 2021;49(3):265-268
File/Dsecription
Figure-1
Model representation of transducer positioning for transabdominal views
Figure-2
Model representation of transducer positioning to transperineal ultrasound
Figure-3
Overview of transducer position during intrapartum ultrasound scanning and identifiable landmarks
Figure-4
Placenta localization (A)Placenta shown overlying the cervix (B) Placenta abutting the cervix
Figure-5
Comparative simulated image (a) for cervical length measurement with the corresponding ultrasound scan image (b)
Figure-6
Comparative simulated image (a) for posterior cervical angle measurement with the corresponding ultrasound scan image (b)
Figure-7
Comparative simulated image (a) for measurement of SPA with the corresponding ultrasound scan image (b)
Figure-8
Comparative illustrated image (a) of the obstetric conjugate with the corresponding ultrasound image (b)
Figure-9
Comparative simulated image (a) for measurement of levator hiatus with the corresponding ultrasound scan image (b).
Figure-10
Classification of fetal occiput position
Figure-11
Transabdominal ultrasound imaging in the transverse plane for locating the fetal spine
Figure-12
Transabdominal suprapubic ultrasound evaluating for fetal position in transverse plane
figure-13
: Transabdominal suprapubic ultrasound imaging for fetal position in the sagittal plane
Figure-14
Ultrasound head station and head direction: Head direction is the angle formed by the longest visible axis of the fetal head with the pubic symphysis
Figure-15
Comparative simulated image with transperineal ultrasound depicting measurement of head-perineum distance
Figure-16
Summary of technique in measuring AoP
Figure-17
Comparative simulated image (A) Simulation model depicting anatomical landmarks to measure
Figure-18
Transperineal ultrasound depiction of caput succedaneum and cranial molding
Figure-19
Schematic model and corresponding transperineal ultrasound measurement of MLA
Figure-20
Summary of OSA- Occiput-spine angle technique
Figure-21
Schematic representation of OSA measurement and corresponding ultrasound image
Figure-22
Assessment of the occiput-spine angle (OSA) in fetuses with occiput anterior position
Figure-23
Summary of CCA technique
Figure-24
Measurement of “chin-to-chest” angle (CCA) in fetuses with occiput posterior position: placement of transducer, illustration, measurement
Figure-25
Visual assessment of the “chin-to-chest” angle (CCA) in fetuses with occiput posterior position
Figure-26
Normal uterus immediately after uncomplicated spontaneous birth with complete placental delivery
Figure-27
Normal uterine involution one week after delivery
Figure-28
Placental retention, manual placental release
Figure-29
Application of Bakri balloon
Figure-30
Postpartum hematoma by transabdominal ultrasound
Figure-31
Placental remnant after spontaneous delivery
Figure-32
Uterine arterio-venous vessel malformation (AVM)