The fetal nose bone nomogram according to gestational weeks

Objective

To identify the fetal nasal bone length nomogram in normal pregnancy.

Methods

607 pregnant woman were taken to the study prospectively.The mean ages of the cases were 29.58±5.57 (16-45).A linear relationship were detected between nasal bone length and pregnancy weeks. Nasal Bone = -6,8656+0,8119*GW+(-,008723)*(GW)2 was formulated as quadratic regression equations .Between nasal bone and pregnancy weeks a r=0,948631 relationship was detected.This relationship was positevly and as the pregnancy week increased, the fetal nasal bone value increases. (F=2715,5212; P<0,001).The change in nasal bone lenght is related to pregnancy week as (R2=0,8999).As the weeks of pregnancy progresses, the nasal bone curve’s opening was minimaly downward. Each week of pregnancy corresponds to a mean and standard deviation of the nasal bone were determined.

Results

The fetal nasal bone lenght measured in 654 pregnant woman who applied to our policlinic at 11-14. weeks for routine obstetric follow up. Completely normal pregnancies were studied.The fetusus that anomaly detected (n=32) in ultrasound examination and high risk for karyotype anomalies (n=15) were excluded from the study and with 607 women the study had done. The measurements were made on Toshiba 140 A and Voluson 730 Pro ultrasound device by an experienced professional. SPSS.13 and MEDCALC computer programme were used fort he statistical analysis.

Conclusion

There was a positive and linear relationship between nasal bone length and gestational weeks . We have developed our center’s nomogram and found the ability to compare it with other centers nomogram.

Keywords

Nasal bone, nomogram

Introduction

The nasal bone can be visualised after the tenth week of pregnancy by ultrasound examination. Whenever not measured in the appropriate plan can it causes misinterpretation. The quality of the ultrasound device, oligohydramnios, obesity, the position of the fetus and the quality of the image can be affect the success result. In recent years, the measurement of nasal bone , has been a parameter in the sonographic evaluation of chromosome abnormalities. The risk of karyotype anomaly is increasing, when nasal bone is aplasic in the first trimester , aplasic or hipoplasic in the second and third trimester.The lenght of the nasal bone has been suggested to vary between the races .In the choromosome anomalies, especially in the Down syndrome, the development of the nasal bone canbe slow and smaller. Many measurements nomograms are being used in chromosome anomalies. In recent years, nasal bone measurement began to be used. We aimed to compose our nomogram and datas of nasal bone lenght of our population in this study.

Methods

The fetal nasal bone lenght measured in 654 pregnant woman who applied to our policlinic at 11-14. weeks for routine obstetric follow up.In some women the fetal lenght were measured again during the follow up. The fetusus that anomaly detected (n=32) in ultrasound examination and high risk for karyotype anomalies (n=15) were excluded from the study and with 607 women the study had done. Completely normal pregnancies were studied. The measurements were made on Toshiba 140 A and Voluson 730 Pro ultrasound device by an experienced Professional in Perinatology.Mostly, by using transabdominal ultrasound, in the mid-saggital face profile, the lateral wiev of nasal bone was played, and the limit of the frontal bone and nasal bome detected and nasal bone measured in the end of the nasal bone position. One or more the most accurate measurements were accepted. SPSS.13 ve MEDCALC computer programme were used fort he statistical analysis.

Results

607 pregnant woman were tajen to the study prospectively. The mean ages of the cases were 29.58±5.57 (16-45). A linear relationship were detected between nasal bone length and pregnancy weeks. Nasal Bone = -6,8656+0,8119*GW+(-,008723)*(GW)2 was formulated as quadratic regression equations. This relationship is positevly and as the pregnancy week increased, the fetal nasal bone value increases. (F=2715,5212; P<0,001).The change in nasal bone lenght is related to pregnancy week as R2=0,8999 and this relationship was positive. As the weeks of pregnancy progresses, the nasal bone curve’s opening was minimaly downward (Graphic 1). Each week of pregnancy corresponds to a mean and standard deviation of the nasal bone were determined (Graphic 2).

Discussion

The ossification points of the nose begins to develop from the gristle focus on the middle part after the 10 th week of pregnancy. The vomer bones previously seen like U shaped, then through the advanced weeks takes V shape by recieve combined. In this period of review the gap between the bones can be accidentally considered as absence of the bone.In 1866 Langdon Down noted that a common characteristic of patients with trisomy 21 is a small nose(9).Yayla et al.,reported that work weeks of gestation in the nasal bone and while a linear curve, in our study of the nasal bone length with weeks of gestation showing an improvement with pregnancy in the last week of the nasal bone length has shown a slowdown. Gianferrari et al reported that absence of a nasal bone is a useful marker for Down syndrome, allowing for the identification of nearly half of all affected pregnancies with a very low false-positive rate (10).On ultrasound examination the nasal bone should be measured in neutral position and with an angel of nearly 45 degree. The quality of the ultrasound device is an important factor. The high resolution of the device reduces the error rate.The important parameters that roles on a right measurament are, the quality of the device, the experience of the doctor and causes related to mother and fetus. A good resolution 2D device is sufficient fort he measurement. The differences between race or ethnicity should not be ignored. The nasal bone should not be visualized between 11-14 weeks of pregnancy in 0.5-1 % altough it is normal, especially this ratio is higher in black race. Sivri et al (11), reported that fetal nasal bone length increases by the growing of the fetus. Earliest in 10 weeks of gestation, when the CRL of 42 mm and nasal bone length was 0.8 mm can be measured. The nasal bone was measured as 1.3 ±0.10 mm in the 11 the pregnancy week as earliest. In many recent studies,a positive lineer increase have been showed between nasal bone length and pregnancy weeks.Similar results has been found in our study.In the first half of pregnancy while it showea a lineer increas, this increase has slowed and drawn a parabole which opening was downward in the second half of pregnancy. In the trisomy cases the ossification of the nasal bones are delated. Larose et al., reported that the nasal bone has not been visualised in Down syndrome cases with a rate of 52 % in 11-14 th week of pregnancy and 43 % 14-25 weeks. Cicero et al., reported the nasal bone as hypoplasic ( <2.5 mm) in trisomy 21 cases with 61.8 % and normal fetusus 1.2 % in the 15-22 weeks of pregnancy.From this point , presence of nasal bone hypoplasia is related with approximately 50-fold increased risk trisomi 21 .

Conclusion

As a result, the fetal bone can be measured from the 11 th week of the pregnany up to term pregnancy. The risk of trisomies is increasing, in the presence of aplasia oe hypoplasia of nasal bone. We found oppurtunity of comparison our nomogram with other centers nomogram. We think that it is more proper that to compare our measuraments with our nomogram and for absolute results we need an increase in the number of the patients.

References

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	File/Dsecription
	Graphic 2. The change of nasal bone mean and SD curve according to gestational week.
	Graphic 1. The mean of nasal bone and the change and the data of the SD curve according to gestational week.
	Tablo 1. The mean, min, max and SD values of nasal bone according to GW.