Obesity increases the risk of spontaneous abortion during infertility treatment

Objective: This study examines the relationship between body mass and the risk of spontaneous abortion in a large cohort of patients who received infertility treatment. Research Methods and Procedures: This is a retrospective study using data on pregnancies (n = 2349) achieved after treatment in a tertiary medical center from 1987 to 1999. One pregnancy per subject was included, and the subjects were stratified into five body mass groups based on body mass index (BMI): underweight, < 18.5 kg/m(2); normal, 18.5 to 24.9 kg/m(2); overweight, 25 to 29.9 kg/m(2); obese, 30 to 34.9 kg/m(2); and very obese, greater than or equal to35 kg/m(2). Logistical regression analysis was used. Results: The overall incidence of spontaneous abortion was 20% (476 of 2349). The effect of BMI on the risk of spontaneous abortion was significant after adjusting for several independent risk factors. Compared with the reference group (BMI 18.5 to 24.9 kg/m(2)), underweight women had a similar risk of spontaneous abortion, whereas there was progressive increase of risk in overweight, obese, and very obese groups (p < 0.05, p < 0.01, and p < 0.001, respectively). Discussion: Of all known risk factors for spontaneous abortion, the control of obesity has great significance because it is noninvasive, potentially modifiable, possibly amenable to low cost, and self-manageable by patients. This study established a positive relationship between BMI and the risk of spontaneous abortion in women who became pregnant after assisted reproductive technology treatment.