Objectives
Pre-pregnancy body mass index (BMI) varies by race/ethnicity and modifies the
association between gestational weight gain (GWG) and adverse pregnancy outcomes, which
disproportionately affect racial/ethnic minorities. Yet studies investigating whether
racial/ethnic disparities in GWG vary by pre-pregnancy BMI are inconsistent, and none
studied nationally representative populations.
Methods
Using categorical measures of GWG adequacy based on Institute of Medicine
recommendations, we investigated whether associations between race/ethnicity and GWG
adequacy were modified by pre-pregnancy BMI [underweight
(<18.5kg/m2), normal weight (18.5-24.9 kg/m2),
overweight (25.0-29.9 kg/m2), or obese (≥30.0 kg/m2)
] among all births to Black, Hispanic, and White mothers in the 1979 USA
National Longitudinal Survey of Youth cohort (n=6849 pregnancies;
range=1-10). We used generalized estimating equations, adjusted for marital
status, parity, smoking during pregnancy, gestational age, and multiple measures of
socioeconomic position.
Results
Effect measure modification between race/ethnicity and pre-pregnancy BMI was
significant for inadequate GWG (Wald test p-value=0.08). Normal weight Black
(Risk Ratio (RR)=1.34, 95% confidence interval (CI): 1.18, 1.52) and
Hispanic women (RR=1.33, 95%CI: 1.15, 1.54) and underweight Black women
(RR=1.38; 95% CI: 1.07, 1.79) experienced an increased risk of
inadequate GWG compared to Whites. Differences in risk of inadequate GWG between
minority women, compared to White women, were not significant among overweight and obese
women. Effect measure modification between race/ethnicity and pre-pregnancy BMI was not
significant for excessive GWG.
Conclusions
The magnitude of racial/ethnic disparities in inadequate GWG appears to vary by
pre-pregnancy weight class, which should be considered when designing interventions to
close racial/ethnic gaps in healthy GWG.