Abstract
OBJECTIVE: Fetal growth standards determine which fetuses are diagnosed with fetal growth restriction (FGR) and become candidates for enhanced fetal monitoring. Given the existence of race-based differences in fetal and neonatal weights, we sought to determine the impact of race-based customization of fetal growth curves on the antenatal detection of FGR. METHODS: This was a retrospective cohort study of 8731 individuals who identified as either White or Black and delivered a liveborn singleton at Magee-Womens Hospital (MWH), Pittsburgh, PA, USA, between January 2003 and January 2013, with at least one sonographic measurement of estimated fetal weight (EFW) taken at 23-41 weeks' gestation. We compared the rates of antenatal FGR diagnosis when EFW was assessed using three distinct growth standards: (1) a standard used at MWH from 2012 to 2018, customized based on the height, weight, parity and race of the pregnant individual (Cust-Race); (2) the same standard without adjustment for race (Cust-NoRace); and (3) the Hadlock standard. Analyses were stratified by the race of the pregnant individual and classification of the neonate as small-for-gestational age (SGA) based on birth weight < 10(th) percentile. RESULTS: The study population included 1458 (16.7%) individuals who self-identified as Black and 7273 (83.3%) who self-identified as White. SGA was diagnosed in 663 (7.6%) newborns, and was significantly more common in those born to Black vs White individuals (172/1458 (11.8%) vs 491/7273 (6.8%); P < 0.001). Among SGA newborns, 286 (43.1%) had at least one antenatal ultrasound scan that met the diagnostic criteria for FGR using the Cust-Race standard, compared with 306 (46.2%) using Cust-NoRace and 335 (50.5%) using Hadlock; only the difference in FGR diagnosis rate between Cust-Race and Hadlock was significant (P = 0.007). For newborns of Black individuals who were SGA at birth, the Cust-Race growth standard diagnosed 52 (30.2%) cases of antenatal FGR, compared with 72 (41.9%) for Cust-NoRace and 77 (44.8%) for Hadlock; again, only the difference in FGR diagnosis rate between Cust-Race and Hadlock was significant (P = 0.005). The antenatal detection of FGR among newborns of White individuals who were SGA at birth was similar across standards, with 234 (47.7%) detected by Cust-Race, 234 (47.7%) by Cust-NoRace and 258 (52.5%) by Hadlock. CONCLUSIONS: Customization of growth standards with a race variable did not improve the antenatal detection of FGR compared with the Hadlock standard. The Hadlock standard demonstrated an improved ability to detect FGR among Black patients without a negative effect on White patients. Moving away from race-specific growth standards may help to eliminate inequities in resource allocation and reduce racial disparities in obstetric care. © 2025 The Author(s). Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.