The association between gestational weight gain and risk of stillbirth: a population-based cohort study

Purpose To estimate the risk of stillbirth associated with excessive and inadequate weight gain during pregnancy. Methods Retrospective cohort study using the Texas vital records database between 2006 and 2011, with 2,230,310 births (5502 stillbirths) was included for analysis. Pregnancies were categorized as adequate weight gain, excessive weight gain, inadequate weight gain, or weight loss based on the Institute of Medicine 2009 recommendations. Hazard ratios (HRs) for stillbirth were estimated for each gestational weight-gain stratum using adequate weight gain as the comparison group. The analysis was performed separately for each body mass index (BMI) class. Results Both inadequate weight gain and weight loss were associated with an increased risk of stillbirth for all BMI classes except the morbidly obese group. Highest risk was seen in weight-loss groups after 36 completed weeks (normal weight: HR = 18.85 [8.25–43.09]; overweight: HR = 5.87 [2.99–11.55]; obese: HR = 3.44 [2.34–5.05]). Weight loss was associated with reduced stillbirth risk in morbidly obese women between 24 and 28 weeks (HR = 0.56 [0.34–0.95]). Excess weight gain was associated with an increased risk of stillbirth among obese and morbidly obese women, with highest risk after 36 completed weeks (obese: HR = 2.00 [1.55–2.58]; morbidly obese: HR = 3.16 [2.17–4.62]). In contrast, excess weight gain was associated with reduced risk of stillbirth in normal-weight women between 24 and 28 weeks (HR = 0.57 [0.44–0.70]) and in overweight women between 29 and 33 weeks (HR = 0.62 [0.45–0.85]). Analysis for the underweight group was limited by sample size. Both excessive weight gain and inadequate weight gain were not associated with stillbirth in this group. Conclusions Stillbirth risk increased with inadequate weight gain and weight loss in all BMI classes except the morbidly obese group, where weight demonstrated a protective effect. Conversely, excessive weight gain was associated with higher risk of stillbirth among obese and morbidly obese women but was protective against stillbirth in lower weight women.