Obesity has become an epidemic in developed societies. Retrospective studies suggest that obesity is associated with miscarriage in assisted reproduction. The objective of this study was to evaluate whether obesity is associated with miscarriage in spontaneous conception. We conducted a systematic review of published studies with pooled analysis. A literature review was performed. Studies in which fertility drugs or in vitro fertilization were used were excluded, unless data could be extracted for spontaneous conception. Data were compared for obese (body mass index [BMI]: ≥28 or 30 kg/m (2)), overweight (BMI: 25 to 29 kg/m (2)), and normal-weight (BMI: <25 kg/m (2)) women, with pooled odds ratios (ORs). Recurrent miscarriage data were analyzed separately. Six studies met the criteria for a cohort of 28,538 women. Pooled analysis revealed a higher miscarriage rate of 13.6% in 3800 obese versus 10.7% in 17,146 normal-BMI women (OR: 1.31; 95% confidence interval [CI], 1.18 to 1.46). Although the cohort was small, there was a higher prevalence of recurrent early miscarriage in obese versus normal-BMI women (0.4% versus 0.1%; OR: 3.51; 95% CI, 1.03 to 12.01). In women with recurrent miscarriage, there was a higher miscarriage rate in the obese versus nonobese women (46% versus 43%; OR: 1.71; 95% CI, 1.05). Based on retrospective studies, we concluded that obesity is associated with a higher miscarriage rate in women who conceive spontaneously. Larger prospective studies are urgently needed to verify these preliminary results.
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