Racial and ethnic disparities in extremes of fetal growth after gestational diabetes mellitus

The aim of this study was to assess and compare risks of having large- or small-for gestational age (LGA and SGA, respectively) infants born to women with gestational diabetes mellitus (GDM) from ten racial/ethnic groups. LGA and SGA were defined as birthweight > 90th and < 10th percentile, respectively, specific to each racial/ethnic population and infant sex. Risks of LGA and SGA were compared among a retrospective cohort of 29,544 GDM deliveries from Hispanic, non-Hispanic white (NHW), non-Hispanic black (NHB), Filipino, Chinese, Asian Indian, Vietnamese, Korean, Japanese and Pacific Islander (PI) groups of women. Unadjusted LGA and SGA risks varied among the ten groups. For LGA, the highest risk was in infants born to NHB women (17.2%), followed by those born to PI (16.2%), Hispanic (14.5%), NHW (13.1%), Asian Indian (12.8%), Filipino (11.6%) and other Asian (9.6-11.1%) women (p < 0.0001). Compared with NHW, the LGA risk was significantly greater for NHB women with GDM (RR 1.25 [95% CI 1.11-1.40]; p = 0.0001 after adjustment for maternal characteristics). Further adjustment for maternal pre-pregnancy BMI and gestational weight gain in the sub-cohort with available data (n = 8,553) greatly attenuated the elevated LGA risk for NHB women. For SGA, the risks ranged from 5.6% to 11.3% (p = 0.003) where most groups (8/10) had risks that were lower than the population-expected 10% and risks were not significantly different from those in NHW women. These data suggest that variation in extremes of fetal growth associated with GDM deliveries across race/ethnicity can be explained by maternal characteristics, maternal obesity and gestational weight gain. Women should be advised to target a normal weight and appropriate weight gain for pregnancies; this is particularly important for NHB women.