HealthDay News — Overweight and obese women have an increased risk of adverse perinatal and neonatal outcomes compared with normal-weight women, meta-analysis findings indicate.

Absolute risks for poor birth outcomes were greatest for among the heaviest women (BMI 40 kg/m2), with absolute risks ranging from 0.69% to 2.7%, compared with normal-weight women (BMI 20 kg/m2), whose absolute risks ranged from 0.20% to 0.76%, Dagfinn Aune, MS, of the Imperial College London and colleagues reported in the Journal of the American Medical Association.

The optimal pre-pregnancy BMI to prevent fetal and infant death is not known, the researchers noted.

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“Some studies have reported J-shaped associations with a small increase in risk among women with low or moderate BMI (although not statistically significant), while other studies reported a linear association,” they wrote. “Determining whether there are any threshold effects between maternal BMI and fetal and infant death could be important with regard to public health recommendations for women who plan pregnancies.”

So they conducted a systematic review and meta-analysis of cohort studies examining maternal BMI and its association with risk of fetal death, stillbirth and infant death.

The summary relative risk (RR) per 5-unit increase in maternal BMI was 1.21 for fetal death (95% CI: 1.09-1.35; I2=77.6%), 1.24 for stillbirth (95% CI: 1.18-1.30; I2=80%), 1.16 for perinatal death (95% CI: 1.00-1.35; I2=93.7%), 1.15 for neonatal death (95% CI: 1.07-1.23; I2=78.5%), and 1.18 for infant death (95% CI: 1.09-1.28; I2=79%).

Women who had a BMI of 20 (used as the reference standard), 25, and 30 kg/m², respectively, had absolute risks per 10,000 pregnancies of 76, 82, and 102 for fetal death; 40, 48, and 59 for stillbirth; 66, 73, and 86 for perinatal death; 20, 21, and 24 for neonatal death; and 33, 37, and 43, for 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.”


  1. Aune D et al. JAMA 2014; 311(15): 1536-1546.