Maternal body mass index and pregnancy outcome in the Nutrition Collaborative Research Support Program.

This paper uses data from the Nutrition CRSP in Egypt, Mexico and Kenya to examine relationships between maternal BMI and pregnancy outcome. Women were studied from the periconceptional period up to 6 months of lactation. No women in Egypt or Mexico, and only two in Kenya where periods of food shortage occurred, had a BMI < 18 at conception. Women with a lower BMI in Mexico and Kenya gained more weight and fat in pregnancy and lost more weight and fat during lactation. These counter-intuitive relationships affect the interpretation of weight and body composition measures used to assess energy adequacy during pregnancy and lactation. Lower pre-pregnancy BMI predicted lower infant weights at birth and was a risk factor for low birthweight in Kenya. At 3-6 months post partum, maternal BMI was less strongly related to infant size, and the lean body mass component of BMI appeared to be a more important predictor than fatness.