Ultrasound‐derived fetal size nomogram for a sub‐Saharan African population: a longitudinal study

Abstract Objectives To create a fetal size nomogram for use in sub‐Saharan Africa and compare the derived centiles with reference intervals from developed countries. Methods Fetal biometric measurements were obtained at entry to antenatal care (11–22 weeks' gestation) and thereafter at 4‐week intervals from pregnant women enrolled in a longitudinal ultrasound study in Kinshasa, Democratic Republic of Congo. The study population comprised 144 singleton gestations with ultrasound‐derived gestational age within 14 days of the menstrual estimate. A total of 755 monthly ultrasound scans were included with a mean ± SD of 5 ± 1 (range, 2–8) scans per woman. Estimated fetal weight (EFW) was calculated at each ultrasound examination using the Hadlock algorithm. A general mixed‐effects linear regression model that incorporated random effects for both the intercept and slope was fitted to log‐transformed EFW to account for both mean growth and within‐fetus variability in growth. Reference centiles (5 th , 10 th , 50 th , 90 th and 95 th centiles) were derived from this model. Results Nomograms derived from developed populations consistently overestimated the 50 th centile EFW value for Congolese fetuses by roughly 5–12%. Differences observed in the 10 th and 90 th centiles were inconsistent between nomograms, but generally followed a pattern of overestimation that decreased with advancing gestational age. Conclusions In low‐resource settings, endemic malaria and maternal nutritional factors, including low prepregnancy weight and pregnancy weight gain, probably lead to lower fetal weight and utilization of nomograms derived from developed populations is not appropriate. This customized nomogram could provide more applicable reference intervals for diagnosis of intrauterine growth restriction in sub‐Saharan African populations. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.