Maternal obesity and gestational weight gain are risk factors for infant death

Abstract

Objective: Assessment of the joint and independent relationships of gestational weight gain and prepregnancy body mass index (BMI) on risk of infant mortality was performed.

Methods: This study used Pennsylvania linked birth-infant death records (2003-2011) from infants without anomalies born to mothers with prepregnancy BMI categorized as underweight (n = 58,973), normal weight (n = 610,118), overweight (n = 296,630), grade 1 obesity (n = 147,608), grade 2 obesity (n = 71,740), and grade 3 obesity (n = 47,277). Multivariable logistic regression models stratified by BMI category were used to estimate dose-response associations between z scores of gestational weight gain and infant death after confounder adjustment.

Results: Infant mortality risk was lowest among normal-weight women and increased with rising BMI category. For all BMI groups except for grade 3 obesity, there were U-shaped associations between gestational weight gain and risk of infant death. Weight loss and very low weight gain among women with grades 1 and 2 obesity were associated with high risks of infant mortality. However, even when gestational weight gain in women with obesity was optimized, the predicted risk of infant death remained higher than that of normal-weight women.

Conclusions: Interventions aimed at substantially reducing preconception weight among women with obesity and avoiding very low or very high gestational weight gain may reduce risk of infant death.

Figure 1

Adjusted predicted risks of infant death by gestational weight gain z-score among underweight (n=58,973), normal weight (n=610,118, panel B), overweight (n=296,630, panel C), grade 1 obese (n=147,608, panel D), and grade 2 obese (n=71,740, panel E) and grade 3 obese (n=47,277, panel F) mothers, Pennsylvania singleton birth certificates, 2003–2011. The solid lines represent the point estimate and dashed lines represent its 95% confidence bands. The vertical lines indicate the Institute of Medicine recommended weight gain ranges (12.5–18 kg at 40 weeks among underweight; 11.5–16 kg at 40 weeks among normal weight, 7–11.5 kg at 40 weeks among overweight, 5–9 kg at 40 weeks among grade 1, 2, and 3 obese). Risks were set at the population average for maternal age, maternal race/ethnicity, maternal education, marital status, parity, smoking during pregnancy, pre-existing diabetes or hypertension, height, Black racial composition of neighborhood, payment source, urban residence, neonatal care level of the birth facility, and year of birth. Gestational weight gain was modeled using a 4-knot restricted cubic spline.

Figure 2

Gestational weight gain z-score categories in association with the adjusted risk of early neonatal death (<7 days, dark gray boxes), late neonatal death (7 to <28 days, light gray boxes), neonatal death (<28 days, white boxes), and postneonatal death (28 to <365 days, black boxes) among normal weight (n=610,118, panel A), overweight (n=296,630, panel B), grade 1 obese (n=147,608, panel C), and grade 2 obese women (n=71,740, panel D). Z-scores <−1 SD, −1 to +1 SD, and >+1 SD correspond to 40-week gestation total weight gains of <11.2, 11.2 to 23, >23 kg for normal weight; <9.0, 9.0 to 24.6, >24.6 kg for overweight; <5.8, 5.8 to 22.2, >22.2 kg for grade 1 obese; <1.9, 1.9 to 21.1, >21.1 kg for grade 2 obese women.