Assessing fetal growth in Africa: Application of the international WHO and INTERGROWTH-21(st) 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-21(st) 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-21(st) and WHO standards, using the Bland and Altman method to assess agreement. For EFW, we used INTERGROWTH-21(st) 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 10(th) 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-21(st) and closer to that of WHO. Consequently, the proportion of fetuses under 10(th) 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 <10(th) 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 10(th) percentiles of ultrasound parameters or EFW. The proportions of fetuses under the 10(th) percentile threshold for IG21st charts were particularly low, raising questions about its use to identify growth-restricted fetuses in Africa.