Sex-specific associations of maternal birthweight with offspring birthweight in the Omega study

Abstract

PurposeWe investigated nonlinear and offspring sex–specific associations of maternal birthweight (BW) with offspring BW among participants of the Omega study, a pregnancy cohort. MethodsMaternal BW was modeled as a continuous variable, linear spline and binary variable indicating low birthweight (LBW; <2500 vs. ≥2500 grams). Offspring BW was modeled as a continuous and binary variable in regression models. Nonlinearity was assessed using likelihood ratio tests (LRTs) in marginal linear spline models. ResultsFor every 100-gram increase of maternal BW, offspring BW increased by 22.29 (95% CI: 17.57, 27.02) or 23.41 (95% CI: 6.87, 39.96) grams among mothers with normal BW or born macrosomic, respectively, but not among LBW mothers (β = −8.61 grams; 95% CI: −22.88, 5.65; LRT P-value = .0005). For every 100-gram increase in maternal BW, BW of male offspring increased 23.47 (95% CI: 16.75, 30.19) or 25.21 (95% CI: 4.35, 46.07) grams among mothers with normal BW or born macrosomic, respectively, whereas it decreased 31.39 grams (95% CI: −51.63, −11.15) among LBW mothers (LRT P-value < .0001). Corresponding increases in BW of female offspring (16–22 grams) did not differ among mothers with LBW, normal BW or macrosomia (LRT P-value = .9163). ConclusionsMaternal and offspring BW associations are evident among normal BW and macrosomic mothers. These associations differ by offspring sex.