New birthweight and head circumference centiles for gestational ages 24 to 42 weeks
Abstract
Based on 20,713 singleton livebirths at the John Radcliffe Hospital, Oxford, in 1978–1984, we calculated new birthweight and head circumference values for males and females between 24 and 42 weeks of gestation. Among the 803 babies born at or before 34 weeks of gestation, 28% were delivered electively for fetal problems; they were considerably lighter and had smaller heads than infants born after spontaneous preterm labour. As we and others have recommended elsewhere, the electively delivered preterm infants were excluded from the calculation of the new birthweight and head circumference centiles. In our series males were heavier and had larger head circumferences than females at most gestational ages. There were consistent and statistically significant differences in birthweight at all gestational ages from 37 weeks and in head circumference at all gestational ages from 35 weeks.
References (14)
- A. Lucas et al.
Birthweight centiles in preterm infants reappraised
Early Hum. Dev.
(1986) - M. Ounsted et al.
Proportionality and gender in small-for-dates and large-for-dates babies
Early Hum. Dev.
(1981) - R. Usher et al.
Intrauterine growth of live-born Caucasian infants at sea level: standards obtained from measurements in 7 dimensions of infants born between 25 and 44 weeks of gestation
J. Pediatr.
(1969) - W.G. Cochran
Approximate significance levels of the Behrens-Fisher test
Biometrics
(1964) - V. Farr et al.
The value of some external characteristics in the assessment of gestational age at birth
Dev. Med. Child Neurol
(1966) - D. Gairdner et al.
A growth chart for premature and other infants
Arch. Dis. Child
(1971) - D.V. Keen et al.
Birthweight between 14 and 42 weeks' gestation
Arch. Dis. Child
(1985)
Cited by (423)
Performance of fetal ultrasound and magnetic resonance imaging in predicting birthweight according to the test-to-delivery interval: A cohort study
2024, European Journal of Obstetrics and Gynecology and Reproductive BiologyTo assess the influence of the test-to-delivery interval (TDI) on the performance of ultrasound (US) and magnetic resonance imaging (MRI) for predicting birthweight (BW).
This is a secondary analysis of a prospective, single center, blinded cohort study that compared MRI and US for the prediction of BW ≥ 95th percentile in singleton pregnancies. Patients that were included in the initial study underwent US and MRI for estimation of fetal weight between 36 + 0/7 and 36 + 6/7 weeks of gestation (WG). The primary outcome of the current study was to report the changes of US and MRI sensitivity and specificity in the prediction of BW > 95th percentile, BW > 90th percentile, BW < 10th percentile, and BW < 5th percentile, according to the TDI. The secondary outcome was to represent the performance of both tools in the prediction of BW > 90th percentile when TDI is<2 weeks, between 2 and 4 weeks, and>4 weeks. Receiver operating characteristic (ROC) curves were constructed accordingly.
2378 patients were eligible for final analysis. For the prediction of BW > 95th or 90th percentile, the sensitivity of MRI remains high until 2 weeks, and it decreases slowly between 2 and 4 weeks, in contrast to the sensitivity of US which decreases rapidly 2 weeks after examination (p < 0.001). For the prediction of BW < 10th or 5th percentile, the sensitivity of both tools decreases in parallel between 1 and 2 weeks. The specificities of both tools remain high from examination till delivery. These findings are reproducible with the use of the antenatal customized and the postnatal national growth charts.
The performance of MRI in the prediction of BW, especially in large-for-gestational age, is maximal when delivery occurs within two weeks of the examination, decreasing slightly thereafter, in contrast with the performance of US which decreases drastically over time.
The impact of different growth charts on birthweight prediction: obstetrical ultrasound vs magnetic resonance imaging
2023, American Journal of Obstetrics and Gynecology MFMThe estimation of fetal weight by fetal magnetic resonance imaging is a simple and rapid method with a high sensitivity in predicting birthweight in comparison with ultrasound. Several national and international growth charts are currently in use, but there is substantial heterogeneity among these charts due to variations in the selected populations from which they were derived, in methodologies, and in statistical analysis of data.
This study aimed to compare the performance of magnetic resonance imaging and ultrasound for the prediction of birthweight using 3 commonly used fetal growth charts: the INTERGROWTH-21st Project, World Health Organization, and Fetal Medicine Foundation charts.
Data derived from a prospective, single-center, blinded cohort study that compared the performance of magnetic resonance imaging and ultrasound between 36+0/7 and 36+6/7 weeks of gestation for the prediction of birthweight ≥95th percentile were reanalyzed. Estimated fetal weight was categorized as above or below the 5th, 10th, 90th, and 95th percentile according to the 3 growth charts. Birthweight was similarly categorized according to the birthweight standards of each chart. The performances of ultrasound and magnetic resonance imaging for the prediction of birthweight <5th, <10th, >90th, and >95th percentile using the different growth charts were compared. Data were analyzed with R software, version 4.1.2. The comparison of sensitivity and specificity was done using McNemar and exact binomial tests. P values <.05 were considered statistically significant.
A total of 2378 women were eligible for final analysis. Ultrasound and magnetic resonance imaging were performed at a median gestational age of 36+3/7 weeks, delivery occurred at a median gestational age of 39+3/7 weeks, and median birthweight was 3380 g. The incidences of birthweight <5th and <10th percentiles were highest with the Fetal Medicine Foundation chart and lowest with the INTERGROWTH-21st chart, whereas the incidences of birthweight >90th and >95th percentiles were lowest with the Fetal Medicine Foundation chart and highest with the INTERGROWTH-21st chart. The sensitivity of magnetic resonance imaging with an estimated fetal weight >95th percentile in the prediction of birthweight >95th percentile was significantly higher than that of ultrasound across the 3 growth charts; however, its specificity was slightly lower than that of ultrasound. In contrast, the sensitivity of magnetic resonance imaging with an estimated fetal weight <10th percentile for predicting birthweight <10th percentile was significantly lower than that of ultrasound in the INTERGROWTH-21st and Fetal Medicine Foundation charts, whereas the specificity and positive predictive value of magnetic resonance imaging were significantly higher than those of ultrasound for all 3 charts. Findings for the prediction of birthweight >90th percentile were close to those of birthweight >95th percentile, and findings for the prediction of birthweight <5th percentile were close to those of birthweight <10th percentile.
The sensitivity of magnetic resonance imaging is superior to that of ultrasound for the prediction of large for gestational age fetuses and inferior to that of ultrasound for the prediction of small for gestational age fetuses across the 3 different growth charts. The reverse is true for the specificity of magnetic resonance imaging in comparison with that of ultrasound.
Diverse mechanisms underlying the fetal growth course in gastroschisis and omphalocele
2023, AJOG Global ReportsGastroschisis and omphalocele are the 2 most common congenital fetal abdominal wall defects. Both malformations are commonly associated with small-for-gestational-age neonates. However, the extent and causes of growth restriction remain controversial in both gastroschisis and omphalocele without associated malformations or aneuploidy.
This study aimed to examine the role of the placenta and the birthweight–to–placental weight ratio in fetuses with abdominal wall defects.
This study included all cases of abdominal wall defects examined at our hospital between January 2001 and December 2020, retrieving the data from the hospital's software. Fetuses with any other combined congenital anomalies, known chromosomal abnormalities, or lost to follow-up were excluded. Overall, 28 singleton pregnancies with gastroschisis and 24 singleton pregnancies with omphalocele met the inclusion criteria. Patient characteristics and pregnancy outcomes were reviewed. The primary outcome was to investigate the association between birthweight and placental weight in pregnancies with abdominal wall defects as measured after delivery. To correct for gestational age and to compare total placental weights, ratios between the observed and expected birthweights for the given gestational age in singletons were calculated. The scaling exponent β was compared with the reference value of 0.75. Statistical analysis was performed using GraphPad Prism (version 8.2.1; GraphPad Software, San Diego, CA) and IBM SPSS Statistics. A P value of <.05 indicated statistical significance.
Women pregnant with a fetus with gastroschisis were significantly younger and more often nulliparous. In addition, in this group, the gestational age of delivery was significantly earlier and almost exclusively for cesarean delivery. Of 28 children, 13 (46.7%) were born small for gestational age, only 3 of them (10.7%) had a placental weight <10th percentile. There is no correlation between birthweight percentiles and placental weight percentiles (P=not significant). However, in the omphalocele group, 4 of 24 children (16.7%) were born small for gestational age (<10th percentile), and all children also had a placental weight <10th percentile. There is a significant correlation between birthweight percentiles and placental weight percentiles (P<.0001). The birthweight–to–placental weight ratio differs significantly between pregnancies diagnosed with gastroschisis and pregnancies diagnosed with omphalocele (4.48 [3.79–4.91] vs 6.05 [5.38–6.47], respectively; P<.0001). Allometric metabolic scaling revealed that placentas complicated by gastroschisis and placentas complicated by omphalocele do not scale with birthweight.
Fetuses with gastroschisis displayed impaired intrauterine growth, which seemed to differ from the classical placental insufficiency growth restriction.
Reducing macrosomia-related birth complications in primigravid women: ultrasound- and magnetic resonance imaging–based models
2023, American Journal of Obstetrics and GynecologyMany complications increase with macrosomia, which is defined as birthweight of ≥4000 g. The ability to estimate when the fetus would exceed 4000 g could help to guide decisions surrounding the optimal timing of delivery. To the best of our knowledge, there is no available tool to perform this estimation independent of the currently available growth charts.
This study aimed to develop ultrasound- and magnetic resonance imaging–based models to estimate at which gestational age the birthweight would exceed 4000 g, evaluate their predictive performance, and assess the effect of each model in reducing adverse outcomes in a prospectively collected cohort.
This study was a subgroup analysis of women who were recruited for the estimation of fetal weight by ultrasound and magnetic resonance imaging at 36 0/7 to 36 6/7 weeks of gestation. Primigravid women who were eligible for normal vaginal delivery were selected. Multiparous patients, patients with preeclampsia spectrum, patients with elective cesarean delivery, and patients with contraindications for normal vaginal delivery were excluded. Of note, 2 linear models were built for the magnetic resonance imaging– and ultrasound-based models to predict a birthweight of ≥4000 g. Moreover, 2 formulas were created to predict the gestational age at which birthweight will reach 4000 g (predicted gestational age); one was based on the magnetic resonance imaging model, and the second one was based on the ultrasound model. This study compared the adverse birth outcomes, such as intrapartum cesarean delivery, operative vaginal delivery, anal sphincter injury, postpartum hemorrhage, shoulder dystocia, brachial plexus injury, Apgar score of <7 at 5 minutes of life, neonatal intensive care unit admission, and intracranial hemorrhage in the group of patients who delivered after the predicted gestational age according to the magnetic resonance imaging–based or the ultrasound-based models with those who delivered before the predicted gestational age by each model, respectively.
Of 2378 patients, 732 (30.8%) were eligible for inclusion in the current study. The median gestational age at birth was 39.86 weeks of gestation (interquartile range, 39.00–40.57), the median birthweight was 3340 g (interquartile range, 3080–3650), and 63 patients (8.6%) had a birthweight of ≥4000 g. Prepregnancy body mass index, geographic origin, gestational age at birth, and fetal body volume were retained for the optimal magnetic resonance imaging–based model, whereas maternal age, gestational diabetes mellitus, diabetes mellitus type 1 or 2, geographic origin, fetal gender, gestational age at birth, and estimated fetal weight were retained for the optimal ultrasound-based model. The performance of the first model was significantly better than the second model (area under the curve: 0.98 vs 0.89, respectively; P<.001). The group of patients who delivered after the predicted gestational age by the first model (n=40) had a higher risk of cesarean delivery, postpartum hemorrhage, and shoulder dystocia (adjusted odds ratio: 3.15, 4.50, and 9.67, respectively) than the group who delivered before this limit. Similarly, the group who delivered after the predicted gestational age by the second model (n=25) had a higher risk of cesarean delivery and postpartum hemorrhage (adjusted odds ratio: 5.27 and 6.74, respectively) than the group who delivered before this limit.
The clinical use of magnetic resonance imaging– and ultrasound-based models, which predict a gestational age at which birthweight will exceed 4000 g, may reduce macrosomia-related adverse outcomes in a primigravid population. The magnetic resonance imaging–based model is better for the identification of the highest-risk patients.
Fetal magnetic resonance imaging at 36 weeks predicts neonatal macrosomia: the PREMACRO study
2022, American Journal of Obstetrics and GynecologyLarge-for-gestational-age fetuses are at increased risk of perinatal morbidity and mortality. Magnetic resonance imaging seems to be more accurate than ultrasound in the prediction of macrosomia; however, there is no well-powered study comparing magnetic resonance imaging with ultrasound in routine pregnancies.
This study aimed to prospectively compare estimates of fetal weight based on 2-dimensional ultrasound and magnetic resonance imaging with actual birthweights in routine pregnancies.
From May 2016 to February 2019, women received counseling at the 36-week clinic. Written informed consent was obtained for this Ethics Committee-approved study. In this prospective, single-center, blinded study, pregnant women with singleton pregnancies between 36 0/7 and 36 6/7 weeks’ gestation underwent both standard evaluation of estimated fetal weight with ultrasound according to Hadlock et al and magnetic resonance imaging according to the formula developed by Baker et al, based on the measurement of the fetal body volume. Participants and clinicians were aware of the results of the ultrasound but blinded to the magnetic resonance imaging estimates. Birthweight percentile was considered as the gold standard for the ultrasound and magnetic resonance imaging–derived percentiles. The primary outcome was the area under the receiver operating characteristic curve for the prediction of large-for-gestation-age neonates with birthweights of ≥95th percentile. Secondary outcomes included the comparative prediction of large-for-gestation-age neonates with birthweights of ≥90th, 97th, and 99th percentiles and small-for-gestational-age neonates with birthweights of ≤10th, 5th, and 3rd percentiles for gestational age and maternal and perinatal complications.
Of 2914 women who were initially approached, results from 2378 were available for analysis. Total fetal body volume measurements were possible for all fetuses, and the time required to perform the planimetric measurements by magnetic resonance imaging was 3.0 minutes (range, 1.3–5.6). The area under the receiver operating characteristic curve for the prediction of a birthweight of ≥95th percentile was 0.985 using prenatal magnetic resonance imaging and 0.900 using ultrasound (difference=0.085, P<.001; standard error, 0.020). For a fixed false-positive rate of 5%, magnetic resonance imaging for the estimation of fetal weight detected 80.0% (71.1–87.2) of birthweight of ≥95th percentile, whereas ultrasound for the estimation of fetal weight detected 59.1% (49.0–68.5) of birthweight of ≥95th percentile. The positive predictive value was 42.6% (37.8–47.7) for the estimation of fetal weight using magnetic resonance imaging and 35.4% (30.1–41.1) for the estimation of fetal weight using ultrasound, and the negative predictive value was 99.0% (98.6–99.3) for the estimation of fetal weight using magnetic resonance imaging and 98.0% (97.6–98.4) for the estimation of fetal weight using ultrasound. For a fixed false-positive rate of 10%, magnetic resonance imaging for the estimation of fetal weight detected 92.4% (85.5–96.7) of birthweight of ≥95th percentile, whereas ultrasound for the estimation of fetal weight detected 76.2% (66.9–84.0) of birthweight of ≥95th percentile. The positive predictive value was 29.9% (27.2–32.8) for the estimation of fetal weight using magnetic resonance imaging and 26.2% (23.2–29.4) for the estimation of fetal weight using ultrasound, and the negative predictive value was 99.6 (99.2–99.8) for the estimation of fetal weight using magnetic resonance imaging and 98.8 (98.4–99.2) for the estimation of fetal weight using ultrasound. The area under the receiver operating characteristic curves for the prediction of large-for-gestational-age neonates with birthweights of ≥90th, 97th, and 99th percentiles and small-for-gestational-age neonates with birthweights of ≤10th, 5th, and 3rd percentiles was significantly larger in prenatal magnetic resonance imaging than in ultrasound (P<.05 for all).
At 36 weeks’ gestation, magnetic resonance imaging for the estimation of fetal weight performed significantly better than ultrasound for the estimation of fetal weight in the prediction of large-for-gestational-age neonates with birthweights of ≥95th percentile for gestational age and all other recognized cutoffs for large-for-gestational-age and small-for-gestational-age neonates (P<.05 for all).
Changing physicians’ incentives to control the C-section rate: Evidence from a major health care reform in Iran
2021, Journal of Health EconomicsWe evaluate the effect of a major health care policy in public hospitals which changed the demand and supply side incentives for c-section procedures in 2014 in Iran, where the c-section rate at the time was 55%. Following the reform, vaginal delivery became free for patients. The policy also introduced financial incentives to doctors for performing vaginal deliveries and set a cap on their maximum c-section rate. We show that supply side incentives had a major role in the effectiveness of the programme, after which the national rate reduced by 6 percentage points. This reduction was mainly driven by first-birth mothers. The reform also shifted doctors with high c-section rates out of public hospitals. We cannot find any adverse effect on Apgar score, hospitalisation or mortality; however, gestation length and birth weight significantly increased.