Impact of replacing Chinese ethnicity-specific fetal biometry charts with the INTERGROWTH-21(st) standard

Prediction by uterine artery Doppler screening of small-for-gestational-age neonates at 19-24 weeks' gestation

OBJECTIVE

Small-for-gestational-age (SGA) neonates are at increased risk of perinatal mortality and morbidity. We aimed to investigate the performance of uterine artery pulsatility index (UtA-PI) at 19-24 weeks' gestation to predict the delivery of a SGA neonate in a Chinese population.

METHODS

This was a retrospective cohort study using data obtained between January 2010 and June 2018. Doppler ultrasonography was performed at 19-24 weeks' gestation. SGA was defined as birth weight below the 10th centile according to the INTERGROWTH-21st fetal growth standards. The performance of UtA-PI to predict the delivery of a SGA neonate was assessed using receiver-operating-characteristics (ROC)-curve analysis.

RESULTS

We included 6964 singleton pregnancies, of which 748 (11%) delivered a SGA neonate, including 115 (15%) women with preterm delivery. Increased UtA-PI was associated with an elevated risk of SGA, both in neonates delivered at or after 37 weeks' gestation (term SGA) and those delivered before 37 weeks (preterm SGA). The areas under the ROC curve (AUCs) for UtA-PI were 64.4% (95% CI, 61.5-67.3%) and 75.8% (95% CI, 69.3-82.3%) for term and preterm SGA, respectively. The performance of combined screening by maternal demographic/clinical characteristics and estimated fetal weight in the detection of term and preterm SGA was improved significantly by the addition of UtA-PI, although the increase in AUC was modest (2.4% for term SGA and 4.9% for preterm SGA).

CONCLUSIONS

This is the first Chinese study to evaluate the role of UtA-PI at 19-24 weeks' gestation in the prediction of the delivery of a neonate with SGA. The addition of UtA-PI to traditional risk factors improved the screening performance for SGA, and this improvement was greater in predicting preterm SGA compared with term SGA. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Comparing population-based fetal growth standards in a US cohort

BACKGROUND

No fetal growth standard is currently endorsed for universal use in the United States. Newer standards improve upon the methodologic limitations of older studies; however, before adopting into practice, it is important to know how recent standards perform at identifying fetal undergrowth or overgrowth and at predicting subsequent neonatal morbidity or mortality in US populations.

OBJECTIVE

To compare classification of estimated fetal weight that is <5th or 10th percentile or >90th percentile by 6 population-based fetal growth standards and the ability of these standards to predict a composite of neonatal morbidity and mortality.

STUDY DESIGN

We used data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be cohort, which recruited nulliparous women in the first trimester at 8 US clinical centers (2010-2014). Estimated fetal weight was obtained from ultrasounds at 16 to 21 and 22 to 29 weeks of gestation (N=9534 women). We calculated rates of fetal growth restriction (estimated fetal weight <5th and 10th percentiles; fetal growth restriction<5 and fetal growth restriction<10) and estimated fetal weight >90th percentile (estimated fetal weight>90) from 3 large prospective fetal growth cohorts with similar rigorous methodologies: INTERGROWTH-21, World Health Organization-sex-specific and combined, Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific and unified, and the historic Hadlock reference. To determine whether differential classification of fetal growth restriction or estimated fetal weight >90 among standards was clinically meaningful, we then compared area under the curve and sensitivity of each standard to predict small for gestational age or large for gestational age at birth, composite perinatal morbidity and mortality alone, and small for gestational age or large for gestational age with composite perinatal morbidity and mortality.

RESULTS

The standards classified different proportions of fetal growth restriction and estimated fetal weight>90 for ultrasounds at 16 to 21 (visit 2) and 22 to 29 (visit 3) weeks of gestation. At visit 2, the Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific, World Health Organization sex-specific and World Health Organization-combined identified similar rates of fetal growth restriction<10 (8.4%-8.5%) with the other 2 having lower rates, whereas Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific identified the highest rate of fetal growth restriction<5 (5.0%) compared with the other references. At visit 3, World Health Organization sex-specific classified 9.2% of fetuses as fetal growth restriction<10, whereas the other 5 classified a lower proportion as follows: World Health Organization-combined (8.4%), Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific (7.7%), INTERGROWTH (6.2%), Hadlock (6.1%), and Eunice Kennedy Shriver National Institute of Child Health and Human Development unified (5.1%). INTERGROWTH classified the highest (21.3%) as estimated fetal weight>90 whereas Hadlock classified the lowest (8.3%). When predicting composite perinatal morbidity and mortality in the setting of early-onset fetal growth restriction, World Health Organization had the highest area under the curve of 0.53 (95% confidence interval, 0.51-0.53) for fetal growth restriction<10 at 22 to 29 weeks of gestation, but the areas under the curve were similar among standards (0.52). Sensitivity was generally low across standards (22.7%-29.1%). When predicting small for gestational age birthweight with composite neonatal morbidity or mortality, for fetal growth restriction<10 at 22 to 29 weeks of gestation, World Health Organization sex-specific had the highest area under the curve (0.64; 95% confidence interval, 0.60-0.67) and INTERGROWTH had the lowest (area under the curve=0.58; 95% confidence interval 0.55-0.62), though all standards had low sensitivity (7.0%-9.6%).

CONCLUSION

Despite classifying different proportions of fetuses as fetal growth restriction or estimated fetal weight>90, all standards performed similarly in predicting perinatal morbidity and mortality. Classification of different percentages of fetuses as fetal growth restriction or estimated fetal weight>90 among references may have clinical implications in the management of pregnancies, such as increased antenatal monitoring for fetal growth restriction or cesarean delivery for suspected large for gestational age. Our findings highlight the importance of knowing how standards perform in local populations, but more research is needed to determine if any standard performs better at identifying the risk of morbidity or mortality.

Can the Pfannenstiel skin incision length be adjusted according to the fetal head during elective cesarean delivery?

Objective

The study aims to determine whether the Pfannenstiel skin incision can be adjusted according to the fetal head's occipitofrontal diameter (OFD) during primary cesarean delivery.

Background

Eligible 114 nulliparous women delivered at term by cesarean section in which Pfannenstiel skin incision was performed according to the OFD of the fetal head between June 2017 and September 2021 were included. Excluded cases were non-vertex presentations, all emergency cesarean sections, severe preeclampsia, women in an active phase of the first stage of labor and second stage of labor, placenta previa and low-lying placenta, multiple pregnancies, and uncontrolled gestational diabetes mellitus.

Results

Among 114 eligible nulliparous women, the mean OFD was 116.1 ± 7.2 (99-138) mm, and the measurement of the Pfannenstiel skin incision length, which was performed according to the OFD was found to be 122.8 ± 9.2 (100-155) mm. The difference between OFD and Pfannenstiel incision kept remained within 10 mm in 90 (82.5.2%), 10-20 mm in 17 (15.5%), and more than 20 mm in two women (1.8%). This technique was successful in 109 (95.6%) out of 114 women without extending the skin incision. In five women, skin incision needed to be extended up to 38 mm. In 10 women (8.7%), the rectus abdominis muscle was cut partially to deliver the fetal head. The mean fetal umbilical artery pH was 7.33 ± 0.05. No neonatal hypoxia was encountered in the study.

Conclusion

Pfannenstiel skin incision can be adjusted according to the OFD with minimal margins of error. This technique may provide better cosmetic results by avoiding unnecessarily prolonged incisions with similar newborn outcomes.

Clinical Trial Registration

Clinicaltrials.gov, identifier [NCT05632796].

Reference Values for Birth Weight in Relation to Gestational Age in Poland and Comparison with the Global Percentile Standards

INTRODUCTION

Percentiles of birth weight by gestational age (GA) are an essential tool for clinical assessment and initiating interventions to reduce health risks. Unfortunately, Poland lacks a reference chart for assessing newborn growth based on the national population. This study aimed to establish a national reference range for birth weight percentiles among newborns from singleton deliveries in Poland. Additionally, we sought to compare these percentile charts with the currently used international standards, INTERGROWTH-21 and WHO.

MATERIALS AND METHODS

All singleton live births (n = 3,745,239) reported in Poland between 2010 and 2019 were analyzed. Using the Lambda Mu Sigma (LMS) method, the Generalized Additive Models for Location Scale, and Shape (GAMLSS) package, smoothed percentile charts (3-97) covering GA from 23 to 42 weeks were constructed.

RESULTS

The mean birth weight of boys was 3453 ± 540 g, and this was higher compared with that of girls (3317 ± 509 g). At each gestational age, boys exhibited higher birth weights than girls. The weight range between the 10th and 90th percentiles was 1061 g for boys and 1016 g for girls. Notably, the birth weight of Polish newborns was higher compared to previously published international growth standards.

CONCLUSION

The reference values for birth weight percentiles established in this study for Polish newborns differ from the global standards and are therefore useful for evaluating the growth of newborns within the national population. These findings hold clinical importance in identifying neonates requiring postbirth monitoring.

[Review of the literature on intrauterine and birthweight charts]

OBJECTIVES

To describe the main intrauterine and birthweight charts and review the studies comparing their performance for the identification of infants at risk of adverse perinatal outcomes.

METHODS

We carried out a literature search using Medline and selected the charts most frequently cited in the literature, French charts and those recently published.

RESULTS

Current knowledge on the association between mortality and morbidity and growth anomalies (small and large for gestational age) mostly relies on the use of descriptive charts which describe the weight distribution in unselected populations. Prescriptive charts, which describe ideal growth in low risk populations, have been constructed more recently. Few studies have evaluated whether the thresholds used to identify infants at risk with descriptive charts (such as the 3^rd or the 10^th percentile) are applicable to prescriptive charts. There is a large variability in the percentage of fetuses or newborns identified as being at risk by each chart, with from 3 to 25% having with a weight under the 10^th percentile, regardless of whether descriptive or prescriptive charts are used. The sensitivity and specificity of antenatal screening for small or large for gestational age newborns depends on the chart used to derive estimated fetal weight percentiles.

CONCLUSION

There is marked variability between intrauterine growth charts that can influence the percentage of infants identified as having abnormal growth. These results show that before the adoption of a growth chart, it is essential to evaluate whether it adequately describes the population and its performance for identifying of infants at risk because of growth anomalies.

The accuracy of international and national fetal growth charts in detecting small-for-gestational-age infants using the Lambda-Mu-Sigma method

Objective

To construct a national fetal growth chart using retrospective data and compared its diagnostic accuracy in predicting SGA at birth with existing international growth charts.

Method

This is a retrospective study where datasets from May 2011 to Apr 2020 were extracted to construct the fetal growth chart using the Lambda-Mu-Sigma method. SGA is defined as birth weight <10th centile. The local growth chart's diagnostic accuracy in detecting SGA at birth was evaluated using datasets from May 2020 to Apr 2021 and was compared with the WHO, Hadlock, and INTERGROWTH-21st charts. Balanced accuracy, sensitivity, and specificity were reported.

Results

A total of 68,897 scans were collected and five biometric growth charts were constructed. Our national growth chart achieved an accuracy of 69% and a sensitivity of 42% in identifying SGA at birth. The WHO chart showed similar diagnostic performance as our national growth chart, followed by the Hadlock (67% accuracy and 38% sensitivity) and INTERGROWTH-21st (57% accuracy and 19% sensitivity). The specificities for all charts were 95-96%. All growth charts showed higher accuracy in the third trimester, with an improvement of 8-16%, as compared to that in the second trimester.

Conclusion

Using the Hadlock and INTERGROWTH-21st chart in the Malaysian population may results in misdiagnose of SGA. Our population local chart has slightly higher accuracy in predicting preterm SGA in the second trimester which can enable earlier intervention for babies who are detected as SGA. All growth charts' diagnostic accuracies were poor in the second trimester, suggesting the need of improvising alternative techniques for early detection of SGA to improve fetus outcomes.

Factors associated with small-for-gestational-age births among preterm babies born <2000 g: a multifacility cross-sectional study in Ethiopia

OBJECTIVES

This study aimed to determine the prevalence of small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA); compare variations in multiple risk factors, and identify factors associated with SGA births among preterm babies born <2000 g.

DESIGN

Cross-sectional study.

SETTING

The study was conducted at five public hospitals in Oromia Regional State and Addis Ababa City Administration, Ethiopia.

PARTICIPANTS

531 singleton preterm babies born <2000 g from March 2017 to February 2019.

OUTCOME MEASURES

Birth size-for-gestational-age was an outcome variable. Birth size-for-gestational-age centiles were produced using Intergrowth-21st data. Newborn birth size-for-gestational-age below the 10th percentile were classified as SGA; those>10th to 90th percentiles were classified as AGA; those >90th percentiles, as large-for-gestational-age, according to sex. SGA and AGA prevalence were determined. Babies were compared for variations in multiple risk factors.

RESULTS

Among 531 babies included, the sex distribution was: 55.44% males and 44.56% females. The prevalences of SGA and AGA were 46.14% and 53.86%, respectively. The percentage of SGA was slightly greater among males (47.62%) than females (44.30%), but not statistically significant The prevalence of SGA was significantly varied between pre-eclamptic mothers (32.42%, 95% CI 22.36% to 43.22%) and non-pre-eclamptic mothers (57.94%, 95% CI 53.21% to 62.54%). Mothers who had a history of stillbirth (adjusted OR (AOR) 2.96 95% CI 1.04 to 8.54), pre-eclamptic mothers (AOR 3.36, 95% CI 1.95 to 5.79) and being born extremely low birth weight (AOR 10.48, 95% CI 2.24 to 49.02) were risk factors significantly associated with SGA in this population.

CONCLUSION

Prevalence of SGA was very high in these population in the study area. Maternal pre-eclampsia substantially increases the risk of SGA. Hence, given the negative consequences of SGA, maternal and newborn health frameworks must look for and use evidence on gestational age and birth weight to assess the newborn's risks and direct care.

Conditional standards for the quantification of foetal growth in an ethnic Chinese population: a longitudinal study

This was an observational study of low-risk singleton pregnancies in an ethnic Chinese population. Foetal biometric variables which included biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL) were measured repeatedly. The standard views for measurement were obtained according to INTERGROWTH-21st criteria. A linear mixed model with fractional polynomial regression was used to describe the longitudinal design. The study included 1289 foetuses and a total of 5125 ultrasound scans, of which each foetus was scanned at least three times, the intervals between scans being at least two weeks. The parameters of the linear mixed models were estimated by Stata v.16 (College Station, TX). Using these parameters, the equations of the mean and variance for BPD, HC, AC and FL were constructed. The conditional percentiles or Z scores could be calculated based on the above equations and previous measurements of the same foetus. A spreadsheet was provided for implementation.Impact StatementWhat is already known on this subject? Longitudinal data derived from serial measurements are therefore appropriate for assessing both foetal size and foetal growth. At present, most reference charts of ethnic Chinese foetal biometry are derived from cross-sectional data, which can only assess foetal size.What do the results of this study add? In this study, we have constructed conditional standards for foetal biometry in an ethnic Chinese population and provided a spreadsheet for querying.What are the implications of these findings for clinical practice and/or further research? The conditional standards can be used to assess foetal growth in clinical practice. In the future, we hope that these foetal growth standards can be applied to determine whether abnormal growth increases the risk of adverse outcomes.

Neonatal head circumference by gestation reflects adaptation to maternal body size: comparison of different standards

Neonatal head circumference (HC) not only represents the brain size of Homo sapiens, but is also an important health risk indicator. Addressing a lack of comparative studies on head size and its variability in term and preterm neonates from different populations, we aimed to examine neonatal HC by gestation according to a regional reference and a global standard. Retrospective analysis of data on neonatal HC obtained from the Lithuanian Medical Birth Register from 2001 to 2015 (423 999 newborns of 24–42 gestational weeks). The varying distribution by gestation and sex was estimated using GAMLSS, and the results were compared with the INTERGROWTH-21st standard. Mean HC increased with gestation in both sexes, while its fractional variability fell. The 3rd percentile matched that for INTERGROWTH-21st at all gestations, while the 50th and 97th percentiles were similar up to 27 weeks, but a full channel width higher than INTERGROWTH-21st at term. INTERGROWTH-21st facilitates the evaluation of neonatal HC in early gestations, while in later gestations, the specific features of neonatal HC of a particular population tend to be more precisely represented by regional references.

Assessing fetal growth in Africa: Application of the international WHO and INTERGROWTH-21st standards in a Beninese pregnancy cohort

BACKGROUND

Fetal growth restriction is a major complication of pregnancy and is associated with stillbirth, infant death and child morbidity. Ultrasound monitoring of pregnancy is becoming more common in Africa for fetal growth monitoring in clinical care and research, but many countries have no national growth charts. We evaluated the new international fetal growth standards from INTERGROWTH-21st and WHO in a cohort from southern Benin.

METHODS

Repeated ultrasound and clinical data were collected in women from the preconceptional RECIPAL cohort (241 women with singleton pregnancies, 964 ultrasounds). We modelled fetal biometric parameters including abdominal circumference (AC) and estimated fetal weight (EFW) and compared centiles to INTERGROWTH-21st and WHO standards, using the Bland and Altman method to assess agreement. For EFW, we used INTERGROWTH-21st standards based on their EFW formula (IG21st) as well as a recent update using Hadlock's EFW formula (IG21hl). Proportions of fetuses with measurements under the 10th percentile were compared.

RESULTS

Maternal malaria and anaemia prevalence was 43% and 69% respectively and 11% of women were primigravid. Overall, the centiles in the RECIPAL cohort were higher than that of INTERGROWTH-21st and closer to that of WHO. Consequently, the proportion of fetuses under 10th percentile thresholds was systematically lower when applying IG21st compared to WHO standards. At 27-31 weeks and 33-38 weeks, respectively, 7.4% and 5.6% of fetuses had EFW <10th percentile using IG21hl standards versus 10.7% and 11.6% using WHO standards.

CONCLUSION

Despite high anemia and malaria prevalence in the cohort, IG21st and WHO standards did not identify higher than expected proportions of fetuses under the 10th percentiles of ultrasound parameters or EFW. The proportions of fetuses under the 10th percentile threshold for IG21st charts were particularly low, raising questions about its use to identify growth-restricted fetuses in Africa.

Customized GROW vs INTERGROWTH-21st birthweight standards to identify small for gestational age associated perinatal outcomes at term

BACKGROUND

Fetal growth restriction is associated with stillbirth and other adverse pregnancy outcomes, and use of the correct weight standard is an essential proxy indicator of growth status and perinatal risk.

OBJECTIVE

We sought to assess the performance of two international birthweight standards for their ability to identify perinatal morbidity and mortality indicators associated with small for gestational age (SGA) infants at term.

STUDY DESIGN

This retrospective cohort study used data from a multi-center perinatal quality initiative including a multi-ethnic dataset of 125,826 births from 2012-2017. Of the singleton term births, 92,622 had complete outcome data including stillbirth, neonatal death, 5-minute Apgar <7, neonatal glucose instability and need for newborn transfer to a higher level of care or NICU admission. The customized (GROW) and INTERGROWTH-21^st (IG21) birthweight standards were applied to determine SGA (<10^th centile) according to their respective methods and formulae. Associations with adverse outcomes were expressed as relative risk (RR) with 95% confidence interval (CI) and population attributable fraction (PAF).

RESULTS

GROW classified 9,578 (10.3%) and IG21 classified 4,079 (4.4%) pregnancies as SGA, respectively. For all of the outcomes assessed, GROW identified more SGA infants with adverse outcomes than IG21, including more stillbirths, perinatal deaths, low Apgar scores, glucose instability, newborn seizure and transfers to a higher level of care. Thirteen of the 27 stillbirths (48%) that were SGA by either method were identified as SGA by GROW but not by IG21. Similarly, additional cases of all other adverse outcome indicators were identified by GROW as SGA, while only in one category (glucose instability) did IG21 identify 9 of 295 cases (3.1%) which were not identified as SGA by GROW.

CONCLUSION

Customized assessment using GROW results in increased identification of small for gestational age term babies that are at significantly increased risk of an array of adverse pregnancy outcomes.

Analysis of longitudinal follow-up data of physical growth in singleton full-term small for gestational age infants

OBJECTIVE

This study aimed to investigate the catch-up growth pattern of singleton full-term small for gestational age (SGA) infants in the first year after birth.

METHODS

A single-center retrospective cohort study was performed to assess singleton full-term SGA infants. Weight, length, and head circumference were measured at birth, and at 1, 3, 6, and 12 months of age.

RESULTS

Two hundred ten SGA infants were included in this study. Boys (n = 90) and girls (n = 120) showed a similar gestational age, birth weight, and body length. Weight, length, and head circumference in SGA infants in all age groups increased with age, with the fastest growth stage from birth to 3 months. The speed of weight and head circumference catch-up was higher than that of body length. At 12 months, significant associations of height in boys with height of the fathers, mothers, and both parents combined appeared. The height of girls showed associations with the mothers' and the parents' height.

CONCLUSIONS

Full-term SGA infants grow rapidly after birth, with the fastest growth rate in the first 3 months, as examined by weight, body length, and head circumference. However, the catch-up speed of weight and body length were not balanced in this study.

Performance of six birth-weight and estimated-fetal-weight standards for predicting adverse perinatal outcome: a 10-year nationwide population-based study

OBJECTIVE

To evaluate three birth-weight (BW) standards (Australian population-based, Fenton and INTERGROWTH-21^st ) and three estimated-fetal-weight (EFW) standards (Hadlock, INTERGROWTH-21^st and WHO) for classifying small-for-gestational age (SGA) and large-for-gestational age (LGA) and predicting adverse perinatal outcomes in preterm and term babies.

METHODS

This was a nationwide population-based study conducted on a total of 2.4 million singleton births that occurred from 24 + 0 to 40 + 6 weeks' gestation between 2004 and 2013 in Australia. The performance of the growth charts was evaluated according to SGA and LGA classification, and relative risk (RR) and diagnostic accuracy based on the areas under the receiver-operating-characteristics curves (AUCs) for stillbirth, neonatal death, perinatal death, composite morbidity and a composite of perinatal death and morbidity outcomes. The analysis was stratified according to gestational age at delivery (< 37 + 0 vs ≥ 37 + 0 weeks).

RESULTS

Following exclusions, 2 392 782 singleton births were analyzed. There were significant differences in the SGA and LGA classification and risk of adverse outcomes between the six BW and EFW standards evaluated. For the term group, compared with the other standards, the INTERGROWTH-21^st BW and EFW standards classified half the number of SGA (< 10^th centile) babies (3-4% vs 7-11%) and twice the number of LGA (> 90^th centile) babies (24-25% vs 8-15%), resulting in a smaller cohort of term SGA at higher risk of adverse outcome and a larger LGA cohort at lower risk of adverse outcome. For term SGA (< 3^rd centile) babies, the RR of perinatal death using the two INTERGROWTH-21^st standards was up to 1.5-fold higher than those of the other standards (including the WHO-EFW and Hadlock-EFW), while the INTERGROWTH-21^st -EFW standard indicated a 12-26% reduced risk of perinatal death for LGA cases across centile thresholds. Conversely, for the preterm group, the WHO-EFW and Hadlock-EFW standards identified a higher SGA classification rate than did the other standards (18-19% vs 10-11%) and a 20-65% increased risk of perinatal death in term LGA babies. All BW and EFW charts had similarly poor performance in predicting adverse outcomes, including the composite outcome (AUC range, 0.49-0.62) for both preterm (AUC range, 0.58-0.62) and term (AUC range, 0.49-0.50) cases and across centiles. Furthermore, specific centile thresholds for identifying adverse outcomes varied markedly by chart between BW and EFW standards.

CONCLUSIONS

This study addresses the recurrent problem of identifying fetuses at risk of morbidity and perinatal mortality associated with growth disorders and provides new insights into the applicability of international growth standards. Our findings of marked variation in classification and the similarly poor performance of prescriptive international standards and the other commonly used standards raise questions about whether the prescriptive international standards that were constructed for universal adoption are indeed applicable to a multiethnic population such as that of Australia. Thus, caution is needed when adopting universal standards for clinical and epidemiological use. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Temporal trends and risk of small for gestational age (SGA) infants among Asian American mothers by ethnicity

PURPOSE

To examine the temporal trends and risk of small for gestational age (SGA) phenotypes across Asian American ethnic groups.

METHODS

We conducted a population-based retrospective study using the 1992-2018 natality data files obtained from the National Vital Statistics System. Joinpoint regression modeling was employed to calculate the average annual percentage change in SGA birth rates among Asian American sub-groups and NH-White women. Logistic regression was utilized to compute the adjusted odds ratio and 95% confidence interval for the association between maternal race (Asian American sub-groups vs. NH-White) and SGA birth and its phenotypes.

RESULTS

We analyzed data on 2,821,798 Asian Americans and 62,174,875 NH-White US live-born infants. Overall, NH-Whites had the lowest SGA rates, while all the Asian ethnic groups had almost consistently higher rates during the 27-year period. Disparity in SGA births in the Asian subgroups was observed. Compared to NH-Whites, stratified analyses showed varying and significantly higher odds of any SGA in all Asian ethnic groups. Asian Indians had the highest odds [adjusted odds ratio (AOR) = 2.23, 95% confidence interval (CI) = 2.22-2.23] of any SGA compared to NH-Whites.

CONCLUSIONS

Our findings support the evidence that Asian Americans are not a homogenous group and highlight the need to disentangle these differences when conducting population health research and interventions among Asian Americans.

FIGO (international Federation of Gynecology and obstetrics) initiative on fetal growth: best practice advice for screening, diagnosis, and management of fetal growth restriction

Fetal growth restriction (FGR) is defined as the failure of the fetus to meet its growth potential due to a pathological factor, most commonly placental dysfunction. Worldwide, FGR is a leading cause of stillbirth, neonatal mortality, and short- and long-term morbidity. Ongoing advances in clinical care, especially in definitions, diagnosis, and management of FGR, require efforts to effectively translate these changes to the wide range of obstetric care providers. This article highlights agreements based on current research in the diagnosis and management of FGR, and the areas that need more research to provide further clarification of recommendations. The purpose of this article is to provide a comprehensive summary of available evidence along with practical recommendations concerning the care of pregnancies at risk of or complicated by FGR, with the overall goal to decrease the risk of stillbirth and neonatal mortality and morbidity associated with this condition. To achieve these goals, FIGO (the International Federation of Gynecology and Obstetrics) brought together international experts to review and summarize current knowledge of FGR. This summary is directed at multiple stakeholders, including healthcare providers, healthcare delivery organizations and providers, FIGO member societies, and professional organizations. Recognizing the variation in the resources and expertise available for the management of FGR in different countries or regions, this article attempts to take into consideration the unique aspects of antenatal care in low-resource settings (labelled “LRS” in the recommendations). This was achieved by collaboration with authors and FIGO member societies from low-resource settings such as India, Sub-Saharan Africa, the Middle East, and Latin America.

Reassessment of the risk of birth defects due to Zika virus in Guadeloupe, 2016

BACKGROUND

In the French Territories in the Americas (FTA), the risk of birth defects possibly associated with Zika virus (ZIKV) infection was 7.0% (95%CI: 5.0 to 9.5) among foetuses/infants of 546 women with symptomatic RT-PCR confirmed ZIKV infection during pregnancy. Many of these defects were isolated measurement-based microcephaly (i.e. without any detected brain or clinical abnormalities) or mild neurological conditions. We wanted to estimate the proportion of such minor findings among live births of women who were pregnant in the same region during the outbreak period but who were not infected with ZIKV.

METHODS

In Guadeloupe, pregnant women were recruited at the time of delivery and tested for ZIKV infection. The outcomes of live born infants of ZIKV non-infected women were compared to those of ZIKV-exposed live born infants in Guadeloupe, extracted from the FTA prospective cohort.

RESULTS

Of 490 live born infants without exposure to ZIKV, 42 infants (8.6%, 95%CI: 6.2-11.4) had mild abnormalities that have been described as 'potentially linked to ZIKV infection'; all but one of these was isolated measurement-based microcephaly. Among the 241 live born infants with ZIKV exposure, the proportion of such abnormalities, using the same definition, was similar (6.6%, 95%CI: 3.8-10.6).

CONCLUSIONS

Isolated anthropometric abnormalities and mild neurological conditions were as prevalent among infants with and without in-utero ZIKV exposure. If such abnormalities had not been considered as 'potentially linked to ZIKV' in the original prospective cohort in Guadeloupe, the overall estimate of the risk of birth defects considered due to the virus would have been significantly lower, at approximately 1.6% (95% CI: 0.4-4.1).

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02916732).

Gestational Diabetes Mellitus: Predictive Value of Fetal Growth Measurements by Ultrasonography at 22-24 Weeks: A Retrospective Cohort Study of Medical Records

Early intervention of gestational diabetes mellitus (GDM) is effective in reducing pregnancy disorders. Fetal growth, measured by routine ultrasound scan a few weeks earlier before GDM diagnosis, might be useful to identify women at high risk of GDM. In the study, generalized estimating equations were applied to examine the associations between ultrasonic indicators of abnormal fetal growth at 22–24 weeks and the risk of subsequent GDM diagnosis. Of 44,179 deliveries, 8324 (18.8%) were diagnosed with GDM between 24 and 28 weeks. At 22–24 weeks, fetal head circumference (HC) < 10th, fetal femur length (FL) < 10th, and estimated fetal weight (EFW) < 10th percentile were associated with 13% to 17% increased risks of maternal GDM diagnosis. Small fetal size appeared to be especially predictive of GDM among women who were parous. Fetal growth in the highest decile of abdominal circumference (AC), HC, FL and EFW was not associated with risk of subsequent GDM. The observed mean difference in fetal size across gestation by GDM was small; there was less than 1 mm difference for AC, HC, and FL, and less than 5 g for EFW before 24 weeks. Despite similar mean fetal growth among women who were and were not later diagnosed with GDM, mothers with fetuses in the lowest decile of HC, FL and EFW at 22–24 weeks tended to have higher risk of GDM.

Current use and performance of the different fetal growth charts in the Italian population

OBJECTIVES

The choice of growth charts impacts on screening, diagnosis and clinical management of fetal growth abnormalities. The objectives of the study were to evaluate: 1) the clinical practice at a national level among tertiary referral centers in the use of fetal biometric growth charts; and 2) the impact on fetal growth screening of existing national and international growth charts.

STUDY DESIGN

A questionnaire was sent to 14 Italian tertiary referral centers to explore biometric reference growth charts used in clinical practice. National and international (Intergrowth-21st and World Health Organization) fetal growth charts were tested on a large national cohort of low risk women with singleton uneventful pregnancy derived from a retrospective cross-sectional multicenter study (21 centers). The percentage of fetuses with biometric measurements below and above the 10th and 90th percentile for each biometric parameter and gestational week were calculated for each growth chart. The percentile curves of the study population were calculated by non-linear quantile regressions.

RESULTS

Twelve Italian centers (86 %) answered to the questionnaire showing a wide discrepancy in the use of growth charts for fetal biometry. The cohort included 7347 pregnant women. By applying Intergrowth-21st growth charts the percentage of fetuses with head circumference, abdominal circumference and femur length below the 10th centile was 3.9 %, 3.6 % and 2.3 %, and above the 90th centile 29.9 %, 32.5 % and 46 %, respectively. The percentages for the World Health Organization growth charts for head and abdominal circumferences and femur length were: below the 10th centile 6.3 %, 7.2 % and 5.3 %, and above 90th centile 22.8 %, 21.3 % and 31.9 %, respectively.

CONCLUSIONS

The wide discrepancy in clinical use of fetal growth charts in Italian centers warrants the adoption of an uniform set of charts. Our data suggest that immediate application into clinical practice of international growth charts might result into an under-diagnosis of small for gestational age fetuses and, especially, in an over-diagnosis of large for gestational age fetuses with major consequences for clinical practice. On these grounds, there is an urgent need for a nationwide study for the prospective evaluation of international growth charts and, if needed, the construction and adoption of methodologically robust national growth charts.

Trends of change in the individual contribution of risk factors for small for gestational age over more than 2 decades

PURPOSE

Over the past years, the prevalence of various risk factors for small for gestational age (SGA) neonates has changed. Little is known if there was also a change in the specific contribution of these risk factors to the prevalence of SGA. We aim to identify trends in the specific contribution of various risk factors for SGA by observing their odds ratios (ORs) throughout different time periods.

METHODS

A nested case-control study was conducted. The ORs for selected known risk factors for SGA occurring in three consecutive 8-year intervals between 1988 and 2014 (T1 - 1988-1996; T2 - 1997-2005; T3 - 2006-2014) were compared. Data were retrieved from the medical centre's computerized perinatal database. Multivariable logistic regression models were constructed and ORs were compared to identify the specific contribution of independent risk factors for SGA along the study period.

RESULTS

During the study period, 285,992 pregnancies met the study's inclusion criteria, of which 15,013 (5.25%) were SGA. Between 1988 and 2014, the incidence of SGA increased from 2.6% in 1988 to 2.9% in 2014. Using logistic regression models, nulliparity, maternal age, gestational age, hypertensive disorders of pregnancy, oligohydramnios and pre-gestational diabetes mellitus were found to be independently associated with SGA. While the adjusted ORs (aOR) of hypertensive disorders of pregnancy and pre-gestational diabetes mellitus had increased, aORs for nulliparity, maternal age and gestational age had remained stable over time. Oligohydramnios had demonstrated a mixed trend of change over the time.

CONCLUSION

In our study, the specific contribution of factors associated with SGA had changed over time. Having a better understating of the changes in the specific contribution of different risk factors for SGA may enable obstetricians to provide consultations.

Birth-weight differences at term are explained by placental dysfunction and not by maternal ethnicity. Study in newborns of first generation immigrants

Objective: The aim of the study was to investigate the influence of ethnicity and cerebroplacental ratio (CPR) on the birth weight (BW) of first generation Indo-Pakistan immigrants' newborns.Methods: This was a retrospective study in a mixed population of 620 term Caucasian and Indo-Pakistan pregnancies, evaluated in two reference hospitals of Spain and Italy. All fetuses underwent a scan and Doppler examination within two weeks of delivery. The influence of fetal gender, ethnicity, GA at delivery, CPR, maternal age, height, weight and parity on BW was evaluated by multivariable regression analysis.Results: Newborns of first generation Indo-Pakistan immigrants were smaller than local Caucasian newborns (mean BW mean= 3048 ± 435 g versus 3269 ± 437 g, p < .001). Multivariable regression analysis demonstrated that all studied parameters, but maternal age and ethnicity, were significantly associated with BW. The most important were GA at delivery (partial R² = 0.175, p < .001), CPR (partial R² = 0.032, p < .001), and fetal gender (partial R² = 0,029, p < .001).Conclusions: The propensity to a lower BW, explained by placental dysfunction but not by maternal ethnicity is transmitted to newborns of first generation immigrants. Whatever are the factors implied they persist in the new residential setting.

Adverse birth outcomes and their clinical phenotypes in an urban Zambian cohort

Background: Few cohort studies of pregnancy in sub-Saharan Africa use rigorous gestational age dating and clinical phenotyping. As a result, incidence and risk factors of adverse birth outcomes are inadequately characterized. Methods: The Zambian Preterm Birth Prevention Study (ZAPPS) is a prospective observational cohort established to investigate adverse birth outcomes at a referral hospital in urban Lusaka. This report describes ZAPPS phase I, enrolled August 2015 to September 2017. Women were followed through pregnancy and 42 days postpartum. At delivery, study staff assessed neonatal vital status, birthweight, and sex, and assigned a delivery phenotype. Primary outcomes were: (1) preterm birth (PTB; delivery <37 weeks), (2) small-for-gestational-age (SGA; <10 ^th percentile weight-for-age at birth), and (3) stillbirth (SB; delivery of an infant without signs of life). Results: ZAPPS phase I enrolled 1450 women with median age 27 years (IQR 23-32). Most participants (68%) were multiparous, of whom 41% reported a prior PTB and 14% reported a prior stillbirth. Twins were present in 3% of pregnancies, 3% of women had short cervix (<25mm), 24% of women were HIV seropositive, and 5% were syphilis seropositive. Of 1216 (84%) retained at delivery, 15% were preterm, 18% small-for-gestational-age, and 4% stillborn. PTB risk was higher with prior PTB (aRR 1.88; 95%CI 1.32-2.68), short cervix (aRR 2.62; 95%CI 1.68-4.09), twins (aRR 5.22; 95%CI 3.67-7.43), and antenatal hypertension (aRR 2.04; 95%CI 1.43-2.91). SGA risk was higher with twins (aRR 2.75; 95%CI 1.81-4.18) and antenatal hypertension (aRR 1.62; 95%CI 1.16-2.26). SB risk was higher with short cervix (aRR 6.42; 95%CI 2.56-16.1). Conclusio ns: This study confirms high rates of PTB, SGA, and SB among pregnant women in Lusaka, Zambia. Accurate gestational age dating and careful ascertainment of delivery data are critical to understanding the scope of adverse birth outcomes in low-resource settings.

Adverse birth outcomes and their clinical phenotypes in an urban Zambian cohort

Background: Few cohort studies of pregnancy in sub-Saharan Africa use rigorous gestational age dating and clinical phenotyping. As a result, incidence and risk factors of adverse birth outcomes are inadequately characterized. Methods: The Zambian Preterm Birth Prevention Study (ZAPPS) is a prospective observational cohort established to investigate adverse birth outcomes at a referral hospital in urban Lusaka. This report describes ZAPPS phase I, enrolled August 2015 to September 2017. Women were followed through pregnancy and 42 days postpartum. At delivery, study staff assessed neonatal vital status, birthweight, and sex, and assigned a delivery phenotype. Primary outcomes were: (1) preterm birth (PTB; delivery <37 weeks), (2) small-for-gestational-age (SGA; <10 ^th percentile weight-for-age at birth), and (3) stillbirth (SB; delivery of an infant without signs of life). Results: ZAPPS phase I enrolled 1450 women with median age 27 years (IQR 23-32). Most participants (68%) were multiparous, of whom 41% reported a prior PTB and 14% reported a prior stillbirth. Twins were present in 3% of pregnancies, 3% of women had short cervix (<25mm), 24% of women were HIV seropositive, and 5% were syphilis seropositive. Of 1216 (84%) retained at delivery, 15% were preterm, 18% small-for-gestational-age, and 4% stillborn. PTB risk was higher with prior PTB (aRR 1.88; 95%CI 1.32-2.68), short cervix (aRR 2.62; 95%CI 1.68-4.09), twins (aRR 5.22; 95%CI 3.67-7.43), and antenatal hypertension (aRR 2.04; 95%CI 1.43-2.91). SGA risk was higher with twins (aRR 2.75; 95%CI 1.81-4.18) and antenatal hypertension (aRR 1.62; 95%CI 1.16-2.26). SB risk was higher with short cervix (aRR 6.42; 95%CI 2.56-16.1). Conclusio ns: This study confirms high rates of PTB, SGA, and SB among pregnant women in Lusaka, Zambia. Accurate gestational age dating and careful ascertainment of delivery data are critical to understanding the scope of adverse birth outcomes in low-resource settings.

Comparison of the INTERGROWTH-21st standard and a new reference for head circumference at birth among newborns in Southern China

BACKGROUND

Previous studies proposed that there were racial or ethnic disparities in fetal growth, challenging the use of international standards in specific populations. This study was to evaluate the validity of applying the INTERGROWTH-21st standard to a Chinese population for identifying abnormal head circumference (HC), in comparison with a newly generated local reference.

METHODS

There were 24,257 singletons delivered by low-risk mothers in four perinatal health-care centers in Southern China. New HC reference was constructed and comparison in distribution of HC categories was performed between the INTERGROWTH-21st standard and new reference after applying these two tools in study population. Logistic regression was used to examine the association between abnormal HC and adverse neonatal outcomes.

RESULTS

There were 4.40% of the newborns identified with microcephaly (HC > 2 standard deviation below the mean) using the INTERGROWTH-21st standard, comparing to the proportion of 2.83% using new reference. The newborns identified with microcephaly only by the INTERGROWTH-21st standard were not at a higher risk of adverse neonatal outcome, compared with those identified as non-microcephaly by both tools (OR 0.73, 95% CI 0.47-1.13).

CONCLUSION

The new HC reference may be more appropriate for newborn assessment in Chinese populations than the INTERGROWTH-21st standard.

Fetal growth standards for Somali population

BACKGROUND

Accurate assessment of fetal size is essential in providing optimal prenatal care. National Institute of Child Health and Human Development (NICHD) study from 2015 demonstrated that estimated fetal weight (EFW) differed significantly by race/ethnicity after 20 weeks. There is a large Somali population residing in Minnesota, many of whom are cared for at our maternal fetal medicine practice at the University of Minnesota. Anecdotally, we noticed an increased proportion of small-for-gestational age diagnoses within this population. We sought to use our ultrasound data to create a reference standard specific for this population and compare to currently applied references.

PURPOSE

We aimed to model fetal growth standards within a healthy Somali population between 16 and 40 weeks gestation, and address possible differences in the growth patterns compared with standards for non-Hispanic White, non-Hispanic Black, Hispanic, and Asian singleton fetuses published by the NICHD in the Fetal Growth Study.

MATERIALS AND METHODS

This is a retrospective cohort study using ultrasound data from 527 low risk pregnancies of Somali ethnicity at single tertiary care center between 2011 and 2017. A total of 1107 scans were identified for these pregnancies and maternal and obstetrical data were reviewed. Women 18-40 years of age with low-risk pregnancies and established dating consistent with first trimester ultrasound scan were included. Exclusion criteria were any maternal, fetal or obstetrical conditions known to affect fetal growth.

RESULTS

Estimated fetal weight among Somali pregnancies differed significantly at some time points from the NICHD four ethnic groups, but generally the EFW graph curves crossed over at most time points between the study groups. At week 18, EFW was significantly larger than all other four ethnic groups (all p<.001), it was also significantly larger from the Hispanic, Black, and Asian ethnic groups at some time points between 18 and 27 weeks gestation (p < .05). Additionally, EFW among Somali pregnancies was significantly smaller than the Black and Asian ethnicity at 32 and 35-36 weeks and smaller than the White ethnicity at 30 and 38-39 weeks (p < .05). Abdominal circumference (AC) for the Somali population was significantly smaller than the other ethnic groups, especially than the White ethnicity at various time points across 16-40 weeks (p < .05). Femur and humerus length were significantly longer when compared to all other ethnic groups at most time points from 16 to 40 weeks of gestation (p < .05). Biparietal diameter (BPD) was significantly smaller than all other ethnic groups specifically at time of fetal survey (18 weeks) and at time of fetal growth assessment (32 weeks) (p < .05).

CONCLUSIONS

Significant differences in fetal growth standards were found between the Somali ethnicity and other ethnic groups (White, Black, Asian, and Hispanic) at various time points from 16 to 40 weeks of gestation. Racial/ethnic-specific standards improve the precision for evaluating fetal growth and may decrease the proportion of fetuses of Somali ethnicity labeled as small-for-gestational age.

Examining the predictive accuracy of metabolomics for small-for-gestational-age babies: a systematic review

INTRODUCTION

To date, there is no robust enough test to predict small-for-gestational-age (SGA) infants, who are at increased lifelong risk of morbidity and mortality.

OBJECTIVE

To determine the accuracy of metabolomics in predicting SGA babies and elucidate which metabolites are predictive of this condition.

DATA SOURCES

Two independent researchers explored 11 electronic databases and grey literature in February 2018 and November 2018, covering publications from 1998 to 2018. Both researchers performed data extraction and quality assessment independently. A third researcher resolved discrepancies.

STUDY ELIGIBILITY CRITERIA

Cohort or nested case-control studies were included which investigated pregnant women and performed metabolomics analysis to evaluate SGA infants. The primary outcome was birth weight <10th centile-as a surrogate for fetal growth restriction-by population-based or customised charts.

STUDY APPRAISAL AND SYNTHESIS METHODS

Two independent researchers extracted data on study design, obstetric variables and sampling, metabolomics technique, chemical class of metabolites, and prediction accuracy measures. Authors were contacted to provide additional data when necessary.

RESULTS

A total of 9181 references were retrieved. Of these, 273 were duplicate, 8760 were removed by title or abstract, and 133 were excluded by full-text content. Thus, 15 studies were included. Only two studies used the fifth centile as a cut-off, and most reports sampled second-trimester pregnant women. Liquid chromatography coupled to mass spectrometry was the most common metabolomics approach. Untargeted studies in the second trimester provided the largest number of predictive metabolites, using maternal blood or hair. Fatty acids, phosphosphingolipids and amino acids were the most prevalent predictive chemical subclasses.

CONCLUSIONS AND IMPLICATIONS

Significant heterogeneity of participant characteristics and methods employed among studies precluded a meta-analysis. Compounds related to lipid metabolism should be validated up to the second trimester in different settings.

PROSPERO REGISTRATION NUMBER

CRD42018089985.

Understanding the relation between Zika virus infection during pregnancy and adverse fetal, infant and child outcomes: a protocol for a systematic review and individual participant data meta-analysis of longitudinal studies of pregnant women and their infants and children

INTRODUCTION

Zika virus (ZIKV) infection during pregnancy is a known cause of microcephaly and other congenital and developmental anomalies. In the absence of a ZIKV vaccine or prophylactics, principal investigators (PIs) and international leaders in ZIKV research have formed the ZIKV Individual Participant Data (IPD) Consortium to identify, collect and synthesise IPD from longitudinal studies of pregnant women that measure ZIKV infection during pregnancy and fetal, infant or child outcomes.

METHODS AND ANALYSIS

We will identify eligible studies through the ZIKV IPD Consortium membership and a systematic review and invite study PIs to participate in the IPD meta-analysis (IPD-MA). We will use the combined dataset to estimate the relative and absolute risk of congenital Zika syndrome (CZS), including microcephaly and late symptomatic congenital infections; identify and explore sources of heterogeneity in those estimates and develop and validate a risk prediction model to identify the pregnancies at the highest risk of CZS or adverse developmental outcomes. The variable accuracy of diagnostic assays and differences in exposure and outcome definitions means that included studies will have a higher level of systematic variability, a component of measurement error, than an IPD-MA of studies of an established pathogen. We will use expert testimony, existing internal and external diagnostic accuracy validation studies and laboratory external quality assessments to inform the distribution of measurement error in our models. We will apply both Bayesian and frequentist methods to directly account for these and other sources of uncertainty.

ETHICS AND DISSEMINATION

The IPD-MA was deemed exempt from ethical review. We will convene a group of patient advocates to evaluate the ethical implications and utility of the risk stratification tool. Findings from these analyses will be shared via national and international conferences and through publication in open access, peer-reviewed journals.

TRIAL REGISTRATION NUMBER

PROSPERO International prospective register of systematic reviews (CRD42017068915).

Fetal anogenital distance using ultrasound

OBJECTIVE

This study measured anogenital distance (AGD) during late second/early third trimester of pregnancy to confirm previous findings that AGD can be measured noninvasively in the fetus using ultrasound and further showed differences in reference ranges between populations.

METHOD

Two hundred ten singleton pregnancies were recruited at the Rosie Hospital, Cambridge, UK. A 2D ultrasound was performed between 26 and 30 weeks of pregnancy. AGD was measured from the centre of the anus to the base of the scrotum in males and to the posterior convergence of the fourchette in females.

RESULTS

A significant difference in AGD between males and females (P < .0001) was found, replicating previous results with a significant correlation between estimated fetal weight (EFW) and AGD in males only (P = .006). A comparison of AGD using reference data from an Israeli sample (n = 118) and our UK sample (n = 208) showed a significant difference (P < .0001) in both males and females, after controlling for gestational age (GA).

CONCLUSION

Our results confirm that AGD measurement in utero using ultrasound is feasible. In addition, there are strong sex differences, consistent with previous suggestions that AGD is influenced by prenatal androgen exposure. AGD lengths differ between the UK and Israel; therefore, population-specific normative values may be required for accurate clinical assessments.

A Comparison of Prediction of Adverse Perinatal Outcomes between Hadlock and INTERGROWTH-21st Standards at the Third Trimester

Little is known about the clinical value of the Hadlock and INTERGROWTH-21^st EFW standards for predicting adverse perinatal outcomes (APOs) in the third trimester. The purpose of this study was to study the association between low estimated fetal weight percentile (EFWc) in the third trimester and the risk of APOs and compare predictions of APOs between Hadlock and INTERGROWTH-21^st EFW standards. A prospective cohort of 690 singleton pregnancies with ultrasonography performed in the third trimester between March 2015 and March 2016 in China was conducted. EFW and the corresponding EFWc were measured using the Hadlock and INTERGROWTH-21^st standards, respectively. Cox proportional hazard models were used to assess the relationship between low EFWc (i.e., <5 percentile, P5) and the risk of APOs. Compared with fetuses with ≥P5 of the EFWc, fetuses with <P5 of the EFWc were much more likely to have an APO, with adjusted hazard ratios of 35.0 (95% confidence interval, 13.9-88.5) and 17.5 (7.7-39.6) for the Hadlock and INTERGROWTH standards, respectively. The Hadlock-EFWc had a higher predictive accuracy for APOs than the INTERGROWTH-EFWc, with area under the receiver operating characteristic curve of 0.94 (0.92-0.95) and 0.90 (0.87-0.92), respectively (P=0.007). The cutoff value for the INTERGROWTH-EFWc was percentile 11.61 with a sensitivity and specificity of 87.9% and 80.5%, respectively. For the Hadlock-EFWc, the corresponding sensitivity and specificity were 93.9% and 81.2%, with a cutoff value of percentile 8.65. Fetuses with low EFWc (i.e., <P5) were associated with an increased risk of APOs. APOs were more accurately predicted when EFWc was measured by the Hadlock standard than by the INTERGROWTH-21^st standard.

Are selection criteria for healthy pregnancies responsible for the gap between fetal growth in the French national Elfe birth cohort and the Intergrowth-21st fetal growth standards?

BACKGROUND

The Intergrowth-21st (IG) project proposed prescriptive fetal growth standards for global use based on ultrasound measurements from a multicounty study of low-risk pregnancies selected using strict criteria. We examined whether the IG standards are appropriate for fetal growth monitoring in France and whether potential differences could be due to IG criteria for "healthy" pregnancies.

METHOD

We analysed data on femur length and abdominal circumference at the second and/or the third recommended ultrasound examination from 14 607 singleton pregnancies from the Elfe national birth cohort. We compared concordance of centile thresholds using the IG standards and current French references and used restricted cubic splines to plot z-scores by gestational age. A "healthy pregnancy" sub-sample was created based on maternal and pregnancy selection criteria, as specified by IG.

RESULTS

Mean gestational age-specific z-scores for femur length and abdominal circumference using French references fluctuated around 0 (-0.2 to 0.1), while those based on IG standards were higher (0.3-0.8). Using IG standards, 2.5% and 5.2% of fetuses at the third ultrasound were <10th centile for femur length and abdominal circumference, respectively, and 31.5% and 16.7% were >90th. Only 34% of pregnancies fulfilled IG low-risk criteria, but sub-analyses yielded very similar results.

CONCLUSION

Intergrowth standards differed from fetal biometric measures in France, including among low-risk pregnancies selected to replicate IG's healthy pregnancy sample. These results challenge the project's assumption that careful constitution of a low-risk population makes it possible to describe normative fetal growth across populations.

Birth-weight differences at term are explained by placental dysfunction and not by maternal ethnicity

OBJECTIVE

To investigate the influence of ethnicity, fetal gender and placental dysfunction on birth weight (BW) in term fetuses of South Asian and Caucasian origin.

METHODS

This was a retrospective study of 627 term pregnancies assessed at two public tertiary hospitals in Spain and Sri Lanka. All fetuses underwent biometry and Doppler examinations within 2 weeks of delivery. The influences of fetal gender and ethnicity, gestational age (GA) at delivery, cerebroplacental ratio (CPR) and maternal age, height, weight and parity on BW were evaluated by multivariable regression analysis.

RESULTS

Fetuses born in Sri Lanka were smaller than those born in Spain (mean BW = 3026 ± 449 g vs 3295 ± 444 g; P < 0.001). Multivariable regression analysis demonstrated that GA at delivery, maternal weight, CPR, maternal height and fetal gender (estimates = 0.168, P < 0.001; 0.006, P < 0.001; 0.092, P = 0.003; 0.009, P = 0.002; 0.081, P = 0.01, respectively) were associated significantly with BW. Conversely, no significant association was noted for maternal ethnicity, age or parity (estimates = -0.010, P = 0.831; 0.005, P = 0.127; 0.035, P = 0.086, respectively). The findings were unchanged when the analysis was repeated using INTERGROWTH-21^st fetal weight centiles instead of BW (log odds, -0.175, P = 0.170 and 0.321, P < 0.001, respectively for ethnicity and CPR).

CONCLUSION

Fetal BW variation at term is less dependent on ethnic origin and better explained by placental dysfunction. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Prospective assessment of INTERGROWTH-21st and World Health Organization estimated fetal weight reference curves

OBJECTIVES

To assess the suitability of the new INTERGROWTH-21^st and World Health Organization (WHO) estimated fetal weight (EFW) references in a Southern Chinese population. A secondary aim was to determine the accuracy of EFW by assessing the difference between EFW and actual birth weight.

METHODS

This was a prospective cross-sectional cohort study. Viable singleton pregnancies at 11-13 weeks' gestation were recruited to undergo a single standardized fetal biometric scan after 20 weeks. The gestational age at which the scan was performed was allocated randomly at the time of recruitment. EFW was predicted using both the Hadlock and INTERGROWTH-21^st weight estimation model formulae. Population-specific EFW references were constructed. Z-scores were used to compare these references against the INTERGROWTH-21^st and WHO international size references. Gestational-age-adjusted projection was used to assess the difference between EFW on the day of delivery and birth weight for fetuses having biometry scans ≥ 34 weeks.

RESULTS

Fetuses of 970 participants had biometry scans. The median number of scans per gestational week was 48 (interquartile range, 43-53). Z-score comparison indicated that the WHO 10^th , 50^th and 90^th centiles of the EFW reference were consistently higher than the corresponding local centiles, whilst the INTERGROWTH-21^st 10^th centile was lower. Fewer than 2% of fetuses scanned at or after 34 weeks would be considered as potentially large-for-gestational age, irrespective of which model was used to predict weight. Adopting the WHO international reference would result in approximately one in six fetuses being regarded as potentially small-for-gestational age, 50% more than the number determined using a population-specific reference. Systematic errors of extrapolated EFW were similar, ranging from 5.5% to 7.4%.

CONCLUSIONS

Centers seeking to use new references, such as the INTERGROWTH-21^st and/or WHO international references, as a means of determining whether a fetus is small- or large-for-gestational age, would be advised to assess the suitability of these references within their own population using standardized methodology. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Customized growth charts: rationale, validation and clinical benefits

Appropriate standards for the assessment of fetal growth and birthweight are central to good clinical care, and have become even more important with increasing evidence that growth-related adverse outcomes are potentially avoidable. Standards need to be evidence based and validated against pregnancy outcome and able to demonstrate utility and effectiveness. A review of proposals by the Intergrowth consortium to adopt their single international standard finds little support for the claim that the cases that it identifies as small are due to malnutrition or stunting, and substantial evidence that there is normal physiologic variation between different countries and ethnic groups. It is possible that the one-size-fits-all standard ends up fitting no one and could be harmful if implemented. An alternative is the concept of country-specific charts that can improve the association between abnormal growth and adverse outcome. However, such standards ignore individual physiologic variation that affects fetal growth, which exists in any heterogeneous population and exceeds intercountry differences. It is therefore more logical to adjust for the characteristics of each mother, taking her ethnic origin and her height, weight, and parity into account, and to set a growth and birthweight standard for each pregnancy against which actual growth can be assessed. A customized standard better reflects adverse pregnancy outcome at both ends of the fetal size spectrum and has increased clinicians' confidence in growth assessment, while providing reassurance when abnormal size merely represents physiologic variation. Rollout in the United Kingdom has proceeded as part of the comprehensive Growth Assessment Protocol (GAP), and has resulted in a steady increase in antenatal detection of babies who are at risk because of fetal growth restriction. This in turn has been accompanied by a year-on-year drop in stillbirth rates to their lowest ever levels in England. A global version of customized growth charts with over 100 ethnic origin categories is being launched in 2018, and will provide an individualized, yet universally applicable, standard for fetal growth.

Evidence-based national guidelines for the management of suspected fetal growth restriction: comparison, consensus, and controversy

Small for gestational age is usually defined as an infant with a birthweight <10th centile for a population or customized standard. Fetal growth restriction refers to a fetus that has failed to reach its biological growth potential because of placental dysfunction. Small-for-gestational-age babies make up 28-45% of nonanomalous stillbirths, and have a higher chance of neurodevelopmental delay, childhood and adult obesity, and metabolic disease. The majority of small-for-gestational-age babies are not recognized before birth. Improved identification, accompanied by surveillance and timely delivery, is associated with reduction in small-for-gestational-age stillbirths. Internationally and regionally, detection of small for gestational age and management of fetal growth problems vary considerably. The aim of this review is to: summarize areas of consensus and controversy between recently published national guidelines on small for gestational age or fetal growth restriction; highlight any recent evidence that should be incorporated into existing guidelines; and identify future research priorities in this field. A search of MEDLINE, Google, and the International Guideline Library identified 6 national guidelines on management of pregnancies complicated by fetal growth restriction/small for gestational age published from 2010 onwards. There is general consensus between guidelines (at least 4 of 6 guidelines in agreement) in early pregnancy risk selection, and use of low-dose aspirin for women with major risk factors for placental insufficiency. All highlight the importance of smoking cessation to prevent small for gestational age. While there is consensus in recommending fundal height measurement in the third trimester, 3 specify the use of a customized growth chart, while 2 recommend McDonald rule. Routine third-trimester scanning is not recommended for small-for-gestational-age screening, while women with major risk factors should have serial scanning in the third trimester. Umbilical artery Doppler studies in suspected small-for-gestational-age pregnancies are universally advised, however there is inconsistency in the recommended frequency for growth scans after diagnosis of small for gestational age/fetal growth restriction (2-4 weekly). In late-onset fetal growth restriction (≥32 weeks) general consensus is to use cerebral Doppler studies to influence surveillance and/or delivery timing. Fetal surveillance methods (most recommend cardiotocography) and recommended timing of delivery vary. There is universal agreement on the use of corticosteroids before birth at <34 weeks, and general consensus on the use of magnesium sulfate for neuroprotection in early-onset fetal growth restriction (<32 weeks). Most guidelines advise using cardiotocography surveillance to plan delivery in fetal growth restriction <32 weeks. The recommended gestation at delivery for fetal growth restriction with absent and reversed end-diastolic velocity varies from 32 to ≥34 weeks and 30 to ≥34 weeks, respectively. Overall, where there is high-quality evidence from randomized controlled trials and meta-analyses, eg, use of umbilical artery Doppler and corticosteroids for delivery <34 weeks, there is a high degree of consistency between national small-for-gestational-age guidelines. This review discusses areas where there is potential for convergence between small-for-gestational-age guidelines based on existing randomized controlled trials of management of small-for-gestational-age pregnancies, and areas of controversy. Research priorities include assessing the utility of late third-trimester scanning to prevent major morbidity and mortality and to investigate the optimum timing of delivery in fetuses with late-onset fetal growth restriction and abnormal Doppler parameters. Prospective studies are needed to compare new international population ultrasound standards with those in current use.

Customized vs INTERGROWTH-21st standards for the assessment of birthweight and stillbirth risk at term

BACKGROUND

Fetal growth abnormalities are linked to stillbirth and other adverse pregnancy outcomes, and use of the correct birthweight standard is essential for accurate assessment of growth status and perinatal risk.

OBJECTIVE

Two competing, conceptually opposite birthweight standards are currently being implemented internationally: customized gestation-related optimal weight (GROW) and INTERGROWTH-21^st. We wanted to compare their performance when applied to a multiethnic international cohort, and evaluate their usefulness in the assessment of stillbirth risk at term.

STUDY DESIGN

We analyzed routinely collected maternity data from 10 countries with a total of 1.25 million term pregnancies in their respective main ethnic groups. The 2 standards were applied to determine small for gestational age (SGA) and large for gestational age (LGA) rates, with associated relative risk and population-attributable risk of stillbirth. The customized standard (GROW) was based on the term optimal weight adjusted for maternal height, weight, parity, and ethnic origin, while INTERGROWTH-21^st was a fixed standard derived from a multiethnic cohort of low-risk pregnancies.

RESULTS

The customized standard showed an average SGA rate of 10.5% (range 10.1-12.7) and LGA rate of 9.5% (range 7.3-9.9) for the set of cohorts. In contrast, there was a wide variation in SGA and LGA rates with INTERGROWTH-21^st, with an average SGA rate of 4.4% (range 3.1-16.8) and LGA rate of 20.6% (range 5.1-27.5). This variation in INTERGROWTH-21^st SGA and LGA rates was correlated closely (R = ±0.98) to the birthweights predicted for the 10 country cohorts by the customized method to derive term optimal weight, suggesting that they were mostly due to physiological variation in birthweight. Of the 10.5% of cases defined as SGA according to the customized standard, 4.3% were also SGA by INTERGROWTH-21^st and had a relative risk of 3.5 (95% confidence interval, 3.1-4.1) for stillbirth. A further 6.3% (60% of the whole customized SGA) were not SGA by INTERGROWTH-21^st, and had a relative risk of 1.9 (95% confidence interval, 3.1-4.1) for stillbirth. An additional 0.2% of cases were SGA by INTERGROWTH-21^st only, and had no increased risk of stillbirth. At the other end, customized assessment classified 9.5% of births as large for gestational age, most of which (9.0%) were also LGA by the INTERGROWTH-21^st standard. INTERGROWTH-21^st identified a further 11.6% as LGA, which, however, had a reduced risk of stillbirth (relative risk, 0.6; 95% confidence interval, 0.5-0.7).

CONCLUSION

Customized assessment resulted in increased identification of small for gestational age and stillbirth risk, while the wide variation in SGA rates using the INTERGROWTH-21^st standard appeared to mostly reflect differences in physiological pregnancy characteristics in the 10 maternity populations.

Estimates of burden and consequences of infants born small for gestational age in low and middle income countries with INTERGROWTH-21st standard: analysis of CHERG datasets

Objectives To estimate small for gestational age birth prevalence and attributable neonatal mortality in low and middle income countries with the INTERGROWTH-21^st birth weight standard.Design Secondary analysis of data from the Child Health Epidemiology Reference Group (CHERG), including 14 birth cohorts with gestational age, birth weight, and neonatal follow-up. Small for gestational age was defined as infants weighing less than the 10th centile birth weight for gestational age and sex with the multiethnic, INTERGROWTH-21^st birth weight standard. Prevalence of small for gestational age and neonatal mortality risk ratios were calculated and pooled among these datasets at the regional level. With available national level data, prevalence of small for gestational age and population attributable fractions of neonatal mortality attributable to small for gestational age were estimated.Setting CHERG birth cohorts from 14 population based sites in low and middle income countries.Main outcome measures In low and middle income countries in the year 2012, the number and proportion of infants born small for gestational age; number and proportion of neonatal deaths attributable to small for gestational age; the number and proportion of neonatal deaths that could be prevented by reducing the prevalence of small for gestational age to 10%.Results In 2012, an estimated 23.3 million infants (uncertainty range 17.6 to 31.9; 19.3% of live births) were born small for gestational age in low and middle income countries. Among these, 11.2 million (0.8 to 15.8) were term and not low birth weight (≥2500 g), 10.7 million (7.6 to 15.0) were term and low birth weight (<2500 g) and 1.5 million (0.9 to 2.6) were preterm. In low and middle income countries, an estimated 606 500 (495 000 to 773 000) neonatal deaths were attributable to infants born small for gestational age, 21.9% of all neonatal deaths. The largest burden was in South Asia, where the prevalence was the highest (34%); about 26% of neonatal deaths were attributable to infants born small for gestational age. Reduction of the prevalence of small for gestational age from 19.3% to 10.0% in these countries could reduce neonatal deaths by 9.2% (254 600 neonatal deaths; 164 800 to 449 700).Conclusions In low and middle income countries, about one in five infants are born small for gestational age, and one in four neonatal deaths are among such infants. Increased efforts are required to improve the quality of care for and survival of these high risk infants in low and middle income countries.