Maternal Body Mass Index and the Risk of Fetal Death, Stillbirth, and Infant Death

IMPORTANCE: Evidence suggests that maternal obesity increases the risk of fetal death, stillbirth, and infant death; however, the optimal body mass index (BMI) for prevention is not known. OBJECTIVE: To conduct a systematic review and meta-analysis of cohort studies of maternal BMI and risk of fetal death, stillbirth, and infant death. DATA SOURCES: The PubMed and Embase databases were searched from inception to January 23, 2014. STUDY SELECTION: Cohort studies reporting adjusted relative risk (RR) estimates for fetal death, stillbirth, or infant death by at least 3 categories of maternal BMI were included. DATA EXTRACTION: Data were extracted by 1 reviewer and checked by the remaining reviewers for accuracy. Summary RRs were estimated using a random-effects model. MAIN OUTCOMES AND MEASURES: Fetal death, stillbirth, and neonatal, perinatal, and infant death. RESULTS: Thirty eight studies (44 publications) with more than 10,147 fetal deaths, more than 16,274 stillbirths, more than 4311 perinatal deaths, 11,294 neonatal deaths, and 4983 infant deaths were included. The summary RR per 5-unit increase in maternal BMI for fetal death was 1.21 (95% CI, 1.09-1.35; I2 = 77.6%; n = 7 studies); for stillbirth, 1.24 (95% CI, 1.18-1.30; I2 = 80%; n = 18 studies); for perinatal death, 1.16 (95% CI, 1.00-1.35; I2 = 93.7%; n = 11 studies); for neonatal death, 1.15 (95% CI, 1.07-1.23; I2 = 78.5%; n = 12 studies); and for infant death, 1.18 (95% CI, 1.09-1.28; I2 = 79%; n = 4 studies). The test for nonlinearity was significant in all analyses but was most pronounced for fetal death. For women with a BMI of 20 (reference standard for all outcomes), 25, and 30, absolute risks per 10,000 pregnancies for fetal death were 76, 82 (95% CI, 76-88), and 102 (95% CI, 93-112); for stillbirth, 40, 48 (95% CI, 46-51), and 59 (95% CI, 55-63); for perinatal death, 66, 73 (95% CI, 67-81), and 86 (95% CI, 76-98); for neonatal death, 20, 21 (95% CI, 19-23), and 24 (95% CI, 22-27); and for infant death, 33, 37 (95% CI, 34-39), and 43 (95% CI, 40-47), respectively. CONCLUSIONS AND RELEVANCE: Even modest increases in maternal BMI were associated with increased risk of fetal death, stillbirth, and neonatal, perinatal, and infant death. Weight management guidelines for women who plan pregnancies should take these findings into consideration to reduce the burden of fetal death, stillbirth, and infant death.