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​Cihat Şen, ​Nicola Volpe

Cecilia Villalain, Daniel Rolnik, M. Mar Gil

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Murat Yayla, Oluş Api

Statistics Editor
Resul Arısoy

Comparison of Fenton and Intergrowth-21st growth charts-A Retrospective study of preterm neonates’ ≤34 weeks.


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Comparison of Fenton and Intergrowth-21st growth charts-A Retrospective study of preterm neonates’ ≤34 weeks.. Perinatal Journal 2023;31(0):- DOI: 10.2399/prn.23.0311002

Author(s) Information


  1. chengalpattu medical college and hospital chengalpattu NEONATOLOGY chengalpattu India
  2. chengalpattu medical college and hospital chengalpattu NEONATOLOGY Chengalpattu India

KIRANKUMAR HARIDAS, chengalpattu medical college and hospital chengalpattu NEONATOLOGY chengalpattu India, [email protected]

Publication History

Manuscript Received: December 05, 2022

Manuscript Accepted: January 14, 2023

Earlyview Date: January 14, 2023

Conflicts of Interest

No conflicts declared.

To compare the Fenton and Intergrowth-21st growth charts in assessing the growth pattern of preterm infants at birth and at discharge.
This is a retrospective study conducted over a period of 1 year. The study included the neonates born ≤34weeks of gestational age who are admitted and stayed for ≥14days in our hospital. The data was collected from discharge sheets and electronic data base. The weight of all babies at birth and at discharge was collected. Growth assessed based on Fenton and Intergrowth-21st growth charts. The  Small for gestational age (SGA) was defined as birth weight ≤-1.28SD. The extrauterine growth restriction (EUGR) status of babies is assessed by a criteria of ≤-1.28SD at discharge.
Most common preterm phenotype was spontaneous preterm labour (47.4%), singleton at birth were 78.9%. The mean gestational age and birth weight of babies were 31.6(±1.42) weeks and 1608.06(±275gms) respectively. The proportion of SGA in our group was 15.2% and 13.5% and AGA were 80.5% and 82.2% by using Intergrowth and Fenton growth charts. The EUGR proportion in our group were 72.8% and 81.3% on Intergrowth-21st and Fenton growth charts respectively using a criteria of ≤-1.28SD at discharge.
There is no statistical difference between Fenton and Intergrowth-21st charts in identifying SGA and EUGR. Whereas the proportion of EUGR is more in Fenton charts than Intergrowth-21st charts.

Fenton, Intergrowth 21st, growth charts, preterm,

The number of preterm infants born every year is around 15 million and it is on the rise. Preterm complications are the leading cause of death among children under 5 years of age accounting for around 1 million in 2015[1].  Those preterm infants who survive the neonatal period develop life time disabilities including learning disabilities, vision and hearing deficits.
So it is necessary to closely monitor the growth in preterm infants to identify any deviations from the normal pattern. As of now there are no ideal growth standard available for interpreting postnatal growth patterns of preterm infants. The current standards are based on the intrauterine growth status. But, there is no international consensus regarding how the growth of preterm neonates should be monitored or what is the ideal pattern of growth in these premature infants. [2]
Revised Fenton growth charts [3] published in 2013 were based on large preterm birth sample collected at different countries. They are used to assign the nutrition status of babies of gestational age till 36 weeks. The advantages of Fenton charts are that, they included the data from recent population-based surveys from multiple countries and sex specific. They are equivalent to WHO growth curves at 50 weeks of post- menstrual age, so after this age WHO growth curves can be used. [4] The disadvantages of these Fenton growth charts are, it is a growth reference and not growth standard and it has variability in methods of measurements of growth parameters. The most important fact about Fenton growth charts is that, they are not considering the postnatal physiological weight loss in the initial days of life and they are targeting an infant's birth percentile which is potentially harmful because it requires rapid weight gain and may cause harmful metabolic consequences in short term and long term as well. [3]
The recently published Intergrowth-21st growth charts are studied by International Fetal and Newborn Consortium with the objective to present prescriptive standards for growth between pregnancy and early infancy. Intergrowth-21st growth standards are developed from prospective study which is more reliable. The advantages of these growth charts are that they considered a large population from different ethnic groups and country. These are also, like Fenton charts are sex specific. [5] The major disadvantage is that, in Intergrowth-21st preterm postnatal follow up study, more than 80% of the preterm neonates were born at 34 weeks’ gestation or later. Only few preterm neonates born at 33 weeks’ gestation or earlier contributed data to the standard and therefore, it cannot be considered as standard for infants born <33 weeks of gestational age. [6]
Although this growth-monitoring tool is based on a healthy preterm cohort and aims to provide a realistic and more appropriate international standard for monitoring of preterm infant’s growth, its universal adaption has been limited by lack of studies that evaluate its performance and functional impact.
The growth of preterm infants is also adversely affected by neonatal morbidities such as necrotizing enterocolitis, gastrointestinal perforations, intraventricular hemorrhage, retinopathy of prematurity, and bronchopulmonary dysplasia. In addition, nutrition related factors such as enteral feeding and parenteral nutrition practices can be significant risk factors for extrauterine growth restriction (EUGR). The very preterm infants are born at increased risk of extrauterine growth restriction.[2,7,] The Vermont Oxford Network study reported that EUGR below the 10th percentile of weight by the Fenton growth chart occurred in 50.3% of very low birth infants (VLBW) infants.[8]
In the present study, it was hypothesized that the incidence of intrauterine and postnatal growth in preterm infants (≤34 weeks) might change when assessed with the new Intergrowth-21st growth standards compared with the Fenton-2013 growth charts.
 This is a retrospective observational study which was conducted in a tertiary care hospital. Our NICU is a tertiary care unit with 20 beds in level 3 and 30 beds in level 2 with annual admission rate of around 3000 infants. All babies’ ≤34weeks of gestational age who were born and admitted to NICU and stayed for more than two weeks in the hospital were included in the study. The criteria of ≥14days was considered as the infants during this period are still in physiologic weight loss and can catch up growth subsequently. Hence these infants can’t be considered as growth restricted.  Exclusion criteria used in the study were any baby born with major congenital anomaly or suspected chromosomal anomaly or syndrome. Infants died during hospital stay were also excluded from the study. Study included infants born between January and December 2019. Data was collected from case sheets and discharge summaries of babies who were admitted in neonatal intensive care unit (NICU), which were present in hospital medical records and in our electronic database. Anthropometric measurement of weight was available for all infants at birth, and at the time of discharge. Two different references were used to asses appropriateness of growth, first one was Intergrowth-21st preterm size at birth and postnatal growth standards for preterm infants and the second was Fenton 2013 growth charts. Birth weight and daily measurements of body weight in our unit is done using electronic weighing scales with accuracy of ±10gms. Z-scores for birth weight were calculated electronically using the Fenton preterm growth charts[3] software accessed from http://  growth charts and the Intergrowth-21st preterm size at birth[4] and postnatal growth standards[5] software accessed from http://intergrowth21. Small for gestational age and large for gestational age was defined as less than or equal to -1.28SD (≤10th percentile) and more than or equal to +1.28SD (≥90th percentile) for gestational age respectively.[9] The extrauterine growth restriction (EUGR) is defined by discharge weight of ≤-1.28SD (10th percentile).[10]
The feeding protocol used in our unit was initiating feeds at 30ml/kg/day on day 1 in infants’ ≤1500gms and 60ml/kg/day in infants>1500gms. The feeds were increased at a rate of 30ml/kg/day for ≥1500gms and 20ml/kg/day for those <1500gms, if baby has no intolerance to initial feeds. We used mother’s own milk (MOM) and if not available then pasteurized donor human milk (PDHM) from institute’s milk bank, is used for the period till MOM is available. We did not use any kind of infant formula in our unit. We did not aspirate the gastric residuals routinely unless there was increase in abdominal girth of ≥2cms from base line. Abdominal girth was monitored before every feed. The infants who require Total parenteral nutrition (TPN) were started proteins at 2gms/kg/day and lipids at 1gm/kg/day on day 1, keeping the protein: calorie ratio of 25-40, by adjusting the glucose infusion rate (GIR). We added Human milk fortifier (HMF) in VLBW infants, if the infant does not gain weight of ≥15gm/kg/day, at a feed volume of ≥180ml/kg/day. If the infant had repeated vomiting or gastric residuals of ≥50% of previous feed volume and hemodynamically unstable, the feeds were restricted to trophic feeds only.  We discharged the infants on feeds of ≥150ml/kg/day, when they gain adequate weight for ≥3 consecutive days and were hemodynamically stable. Small for gestational age (SGA) was defined as ≤-1.28SD (≤10th percentile). The extra-uterine growth restriction (EUGR) status of infants was assessed by using a criteria of ≤-1.28SD (≤10th percentile) at discharge.  Approval from institutional ethical committee was obtained prior to study. As this is a retrospective study the consent from parents was not required.
All the infants born and admitted in our hospital from January to December 2019 were considered for the study. A convenient sample size was considered over a period of one year.  A total of 118 infants were eligible for study based on inclusion criteria.  Continuous variables are represented as mean with standard deviation. Chi square test is applied for categorical variable. Agreement statistics is done by Cohen’s kappa test. Statistics is done by using SPSS version 22.
A total of 423 babies were born and admitted during study period. Among them 118 babies required to stay beyond 14 days in hospital, which constituted our study population, whose details have been collected for analysis. Mean gestational age was 31.6weeks. Spontaneous onset of labour pain (47.4%) and preterm premature of rupture of membranes (24.5%) were found to be the common reason for preterm delivery. Majority of the babies that is 93 (78.8%) out of 118 babies were born out of singleton pregnancy.  The mean birth weight was 1608gms (±275gms). Babies required around 10.4days to reach 150ml/kg/day of feeds and the mean duration of hospital stay was 24.8days. The mean gestational age at discharge was 35.4weeks and mean weight at discharge was 1730gms (±226gms).
The infants with SGA at birth using birth weight as criteria were 18 (15.2%) and 16 (13.5%) with Intergrowth-21st and Fenton growth charts, respectively.  LGA babies were 5 (4.2%) using both growth charts. Only 6% of infants identified as SGA at birth by Fenton were labelled as AGA by Intergrowth-21st charts. Similarly, 16% of SGA infants by Intergrowth-21st charts were labelled as AGA by Fenton. Overall, the identification of birth size had some difference between growth charts.
The EUGR component using ≤-1.28SD was present in 86 (72.8%) and 96 (81.3%) babies using Intergrowth-21st and Fenton growth charts, respectively. Among the EUGR infants identified by Fenton charts, 8.5% of these infants were considered as AGA at discharge by Intergrowth-21st charts. The proportion of EUGR infants identified by Fenton charts were higher compared to Intergrowth-21st growth charts.
The growth of preterm babies following premature birth is a challenge to the caregiver. These premature infants would go through many complications postnatally which hamper their postnatal nutrition, which in short and long term has many complications. [7]   Thus it becomes important to keep watch on nutrition and growth of these premature infants. To keep a watch on growth we need a growth chart which could define the appropriate growth for premature infants.
Fenton growth charts are the one which are commonly used by many NICUs for monitoring growth. Off late, Intergrowth 21st growth charts are published which are supposed to be better as they are prescriptive standards for Preterms and term infants. In this study, we aimed at comparing the Fenton and Intergrowth-21st growth charts in assessing the growth at birth and at discharge to find the difference between these two growth charts.
In a prospective study on 248 premature infants less than 32weeks gestational age, conducted by Tuzun et al [11] found that the small for gestational age (SGA) rate was significantly higher and the EUGR rate was significantly lower with the Intergrowth-21st charts compared with the Fenton’s growth chart. In our study the proportion of SGA babies identified at birth was slightly higher and the EUGR babies were slightly lower in Intergrowth-21st chart compared to Fenton growth chart which was similar to study conducted by Tuzun et al. The difference of IUGR and EUGR in Tuzun et al study found a statistical significance, which in our study, could not find a significant difference on statistical analysis. The reasons could be because of the study infant characteristics, where in, the Tuzun et al and also the rate of maternal complications were high in their study, which could cause IUGR and also had infants who required intensive care at birth than our study infants which could cause EUGR in those infants. In our study we had more number of infants born by spontaneous onset of labour pains without any other cause for prematurity and our infants required intensive care for short period of time.
In a retrospective study conducted by Reddy et al[12]  on 603 premature infants born <32weeks of gestational age found that, the proportion of infants identified as IUGR at birth with respect to weight by Intergrowth-21st chart were higher and also EUGR proportion was higher compared to Fenton growth chart. They also found that the incidence of morbidities in IUGR infants identified by Intergrowth-21st charts were higher. In our study we had similar results as described in Reddy at al study, in terms of identifying IUGR at birth by both charts. This difference could be because of difference in inclusion criteria in our study, which included only those babies who are survived till discharge and also the predominant infant’s population in our study were between 30 and 34 weeks of gestational age, which are expected to have few comorbidities. These difference could have changed the results of morbidity profile in our study. 
In a study conducted by Yitayew et al [13] in infants born between 24-33 weeks of gestational age also found that the SGA rate identified by Intergrowth-21st was high but not significant and the EUGR rate identified was low when compared to Fenton growth charts which was found to be statistically significant. These results were similar to our study infants except for the statistical significance.
In a study conducted by Patel DV et al[14] on 318 preterm infants <37weeks of gestation found that there is poor agreement between the both the growth charts in identifying weight, length and head circumference at birth. Similar to this study, in our study also there is poor agreement between the growth charts after applying Cohen’s kappa test for agreement among growth charts.   
Even though the proportion of SGA at birth was slightly higher in Intergrowth-21st chart compared to Fenton chart, we did not find a statistically significant difference in identifying the SGA at birth after performing a chi square analysis. (Chi square 2.86, p 0.09)
In our study we defined EUGR as ≤-1.28sd.[10] The proportion of EUGR was higher in Fenton charts compared to Intergowth-21st charts but there was statistically no significant difference in EUGR proportions identified by both growth charts after applying chi square test (p value 0.09).
The study conducted by Tuzun et al[11], Reddy et al[12], Yitayew et al[13] and Patel dv et al[14]  found that there was significant difference in identifying the EUGR proportions by both growth charts, contrary to our study, which found no statistical difference. The reason for this contradiction could be due to the difference in sample size used, feeding strategy in our unit, which follows a restricted feeding during the period of illness and also we had more number of mature infants compared to other studies. 
This study has some limitations which we did not include the head circumference and length at birth and at discharge in defining IUGR and EUGR which could have added more insight into the growth of infants in comparing the Intergrowth-21st and Fenton growth charts.
Our study showed that there is no difference in identifying AGA and SGA at birth when using Intergrowth-21st and Fenton growth charts. The proportion of EUGR identified by Intergrowth 21st chart was comparatively less than Fenton charts. Large scale prospective studies to be conducted to compare these growth charts before implementing Intergrowth-21st charts universally as standards for assessing size at birth and also at discharge.
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Maternal and neonatal characteristics
Distribution of infants’ growth at birth and EUGR rate at discharge
Flow chart depicting the study