INTRODUCTION
In the United States, the prevalence of overweight and obesity has reached epidemic proportions, affecting more than 95 million adults.1–3 Obesity contributes to significant morbidity and mortality from several conditions, including heart disease, diabetes, and cancer.4,5 Obesity during pregnancy has been associated with increased risk of fetal macrosomia and medical complications, including pregnancy-induced hypertension, gestational diabetes, and cesarean delivery.6–9 A recent study from Sweden showed that higher maternal pre-pregnancy body mass index (BMI), a measure of weight for height, was associated with an increased risk of adverse pregnancy outcomes.10 The effect differed by parity status, with greater risk of some outcomes, including late fetal death and delivery at or before 32 weeks’ gestation, for pregnancies to nulliparous women. The risk of late fetal death was increased for both obese (BMI≥30.0) and overweight (BMI=25.0–29.9) women compared with women categorized as lean (BMI< 20.0), suggesting that not only pre-pregnancy obesity but also prepregnancy overweight may carry some risk. Many factors associated with perinatal morbidity and mortality are not amenable to intervention. Recent epidemiologic findings indicate that weight control may offer the potential for affecting gestational outcomes, especially among women planning a first pregnancy.10 With this in mind, we conducted a population-based cohort study of the effect of maternal prepregnancy obesity or overweight on pregnancy complications and adverse pregnancy outcomes.
