Impact of race-based customization on detection of fetal growth restriction.

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 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.