A new customized fetal growth standard for African American women: the PRB/NICHD Detroit study

Abstract

Background The assessment of fetal growth disorders requires a standard. Current nomograms for the assessment of fetal growth in African American women have been derived either from neonatal (rather than fetal) biometry data or have not been customized for maternal ethnicity, weight, height, parity, and fetal sex. Objective We sought to 1) develop a new customized fetal growth standard for African American mothers; and 2) compare such a standard to three existing standards for the classification of fetuses as small (SGA) or large (LGA) for gestational age. Study Design A retrospective cohort study included 4,183 women (4,001 African American and 182 Caucasian) from the Detroit metropolitan area who underwent ultrasound examinations between 14 and 40 weeks of gestation (the median number of scans per pregnancy was 5, interquartile range 3-7) and for whom relevant covariate data were available. Longitudinal quantile regression was used to build models defining the “normal” estimated fetal weight (EFW) centiles for gestational age in African American women, adjusted for maternal height, weight, parity, and fetal sex, and excluding pathologic factors with a significant effect on fetal weight. The resulting Perinatology Research Branch/Eunice Kennedy Shriver National Institute of Child Health and Human Development (hereinafter, PRB/NICHD) growth standard was compared to 3 other existing standards—the customized gestation-related optimal weight (GROW) standard; the Eunice Kennedy Shriver National Institute of Child Health and Human Development (hereinafter, NICHD) African American standard; and the multinational World Health Organization (WHO) standard—utilized to screen fetuses for SGA (<10th centile) or LGA (>90th centile) based on the last available ultrasound examination for each pregnancy. Results 1) First, the mean birthweight at 40 weeks was 133g higher for neonates born to Caucasian than to African American mothers and 150g higher for male than female neonates; maternal weight, height, and parity had a positive effect on birthweight.Second, analysis of longitudinal EFW revealed the following features of fetal growth: (1) all weight centiles were about 2% higher for male than for female fetuses; (2) maternal height had a positive effect on EFW, with larger fetuses being affected more (2% increase in the 95th centile of weight for each 10-cm increase in height); and (3) maternal weight and parity had a positive effect on EFW that increased with gestation and varied among the weight centiles. Third, the screen-positive rate for SGA was 7.2% for the NICHD African American standard, 12.3% for the GROW standard, 13% for the WHO standard customized by fetal sex, and 14.4% for the PRB/NICHD customized standard. For all standards, the screen-positive rate for SGA was at least two-fold higher among fetuses delivered preterm than at term.Fourth, the screen-positive rate for LGA was 8.7% for the GROW standard, 9.2% for the PRB/NICHD customized standard, 10.8% for the WHO standard customized by fetal sex, and 12.3% ...

Research update for articles published in EJCI in 2016

“…This is in accordance with findings from other studies 29,30 that the use of the INTER-GROWTH-21st standard underestimates the proportion of SGA live births and SGA infants at risk of perinatal mortality and morbidity. Furthermore, both The Eunice Kennedy Shriver National Institute of Child Health and Human Development A study 31 that was designed to assess whether specific racial/ethnic-specific foetal growth standards were needed and the PRB/NICHD Detroit study 32 concluded that there is highly statistically significant racial/ethnic differences in foetal growth resulting in the publication of racial/ethnic-specific derived standards supporting our findings about the need of customized rather than multinational formulas.…”

Prediction of adverse perinatal outcome by fetal biometry: comparison of customized and population‐based standards

“…For the PRB/NICHD standard, EFW was calculated using the three‐parameter Hadlock formula (HC, AC and FL) and corresponding customized centiles were calculated using the R package available at http://bioinformaticsprb.med.wayne.edu/software/prb-nichd-fetal-growth-standard/. Growth centiles were customized for maternal height, weight and parity, and fetal sex.…”

“…The effects of these factors were assumed to be proportionally constant during gestation, and adjustment coefficients were estimated from birth weight data in specific populations. More recent customized standards do not rely on the proportionality assumption and allow these effects to vary among the specific centile curves.…”

Timing of Delivery in Pregnancies Complicated by Suspected Fetal Growth Restriction without Doppler Abnormalities

“…The PRB/NICHD Detroit study included only black women living in Detroit and classified 11.6% of term black fetuses as SGA, which may be due to their inclusion of pathological pregnancies. 13 The INTERGROWTH study combined multiple racial and ethnic populations from eight countries but included only normal healthy pregnancies, creating in international standard based on the premise that there is no biological basis for variation in fetal growth by population. 14 Whether varied growth curves of different populations of fetuses is physiological or pathological remains debated.…”