Racial disparities in the transgenerational transmission of low birthweight risk

Objective: To examine the association of maternal low birthweight (LBW) with infant LBW and infant LBW subgroups (i.e. moderate and very LBW), overall and among non-Hispanic (NH) white and NH black mothers. Design: We conducted a population-based cohort study in Allegheny County, Pennsylvania, using linked birth record data of NH white and NH black mother-infant pairs (N = 6,633) born in 1979-1998 and 2009-2011, respectively. The exposure of interest was maternal LBW (birthweight <2500 grams) while the outcomes were infant LBW and LBW subgroups - moderate LBW (1,500-2,499 grams) or very LBW (<1,500 grams). Logistic regression (binomial and multinomial) models were used to estimate adjusted Odds Ratios (ORs), Relative Risk Ratios (RRRs), and related 95% confidence intervals (CI). Stratified analyses were conducted to assess effect modification by mothers' race. Results: Maternal LBW was associated with 1.53 (95%CI: 1.15-2.02) and 1.75 (95%CI: 1.29-2.37) -fold increases in risk of infant LBW and MLBW, respectively, but not VLBW (RRR = 0.86; 95%CI: 0.44-1.70). In race-stratified models, maternal LBW-infant LBW associations were observed among NH blacks (OR = 1.88; 95%CI: 1.32-2.66) and not among NH whites (OR = 1.03; 95%CI: 0.62-1.73) (P for interaction = 0.07). Among NH blacks, maternal LBW was associated with a 2.18 (95%CI: 1.49, 3.20) -fold increase in risk of infant MLBW, but not VLBW (RRR = 1.12; 95%CI: 0.54, 2.35). Among NH whites, LBW subgroup analyses could not be performed due to small numbers of VLBW infants among LBW mothers. Conclusion: Mothers who were LBW at their own birth were more likely to have MLBW infants. Maternal race modified associations of maternal LBW with infant LBW, particularly infant MLBW. Further research is needed in this area to understand the potential mechanisms involved in the transgenerational transmission of LBW risk and race-specific differences in the transmission.