SUBFERTILITY AND THE RISK OF LOW-BIRTH-WEIGHT

Objective: We evaluated the association between subfertility and low birth weight infants. Design: Women in this analysis participated in a cross-sectional investigation of maternal risk factors for adverse pregnancy outcomes. Setting: Medical and obstetric history and life style information were obtained from women who delivered at the Boston Hospital for Women, 1977 to 1980. Patients, Participants: Our analysis was restricted to nondiabetic married women who planned their pregnancies and subsequently delivered viable singletons (3,622). The 644 "subfertile" women (no conception during a year of unprotected intercourse) were compared with 2,978 "fertile" women (conception within 1 year). Main Outcome Measure(s): The relative risk of low birth weight was estimated using the cumulative incidence risk ratio. Results: After adjusting for confounding, the relative risk of delivering a low birth weight infant (< 2,500 g) for subfertile women versus fertile women was 1.9 (95% confidence interval [CI], 1.3 to 2.8). The adjusted relative risk of delivering a term low birth weight (intrauterine growth retarded) infant was 2.3 (95% CI, 1.2 to 4.4). Conclusions: In these data, subfertility is a predictor for low birth weight. The association may result from endocrinological, immunological, cervical, or other factors that interfere with optimal fetal growth.