The effect of maternal nutritional status prior to pregnancy on birth outcomes is of great public health importance. Epidemiological studies have shown a clear association between maternal pregravid weight and birth outcomes. As a marker of nutritional status, a woman's pregravid body mass index (BMI = kg/m
2), if low (<19.8 BMI), may reflect chronic nutritional deficiency whereas a high BMI (>26.1 BMI) reflects an imbalance between energy intake and expenditure, and thus varying degrees of adiposity [
1]. The effects of each on birth outcomes differ, with low BMI being associated with intrauterine growth retardation (IUGR), preterm birth, and iron deficiency anemia [
2‐
5]. Whereas, BMI above the normal range of 19.8 to 26.1 (IOM 1990) is associated with a number of adverse reproductive health outcomes. For example, infertility [
6] gestational diabetes [
7], pregnancy induced hypertension and pre-eclampsia [
8], birth defects [
9], large for gestational age (LGA) or macrosomia (>4500 g) [
10], cesarean sections [
11‐
13], prolonged labor [
14], and recently postpartum anemia [
15‐
17] have all been associated with maternal overweight yet the exact mechanisms have not been identified. The purpose of this paper is to describe an overview of the complications associated with maternal overweight and obesity; present updated information on the weight trends among women; and review prevention studies aimed at adolescents and women prior to pregnancy.