What is the recommended weight gain in pregnancy?

Nearly 20 years have passed since guidelines for pregnancy weight gain have been reissued from the Institute of Medicine (IOM). In that time, more research has been completed to better understand the effects of weight gain during pregnancy on the health of both the mother and the infant. Important variables to take into consideration regarding recommended weight gain include twin or triplet pregnancies, the mother’s age, and the mother’s prepregnancy weight.

These variables can add to the burden of chronic disease for the mother and baby; excessive weight gain is associated with an increased risk for gestational diabetes, pregnancy-associated hypertension, and delivery of large-for-gestational-age infants. Because of these risks, the Institute of Medicine has developed new guidelines for weight gain during pregnancy.

Guidelines for weight gain during pregnancy* are as follows:

• Underweight women (BMI < 18.5) should gain 28-40 pounds.
• Normal-weight women (BMI, 18.5-24.9) should gain 25-35 pounds.
• Overweight women (BMI, 25-29.9) should gain 15-25 pounds.
• Obese women (BMI, 30 or higher) should gain 11-20 pounds.

*Weight gain guidelines are for singleton pregnancy; weight gain should be higher for multiple pregnancies.

Clinicians are urged to supplement these guidelines with individualized counseling about diet and exercise, and preconception counseling should emphasize the importance of conceiving when the mother is at a normal body mass index (BMI). To help mothers attain these goals, dietary, lifestyle, and exercise interventions have been shown to be safe and effective at reducing excessive weight gain in pregnancy. In an analysis of 44 studies that evaluated the efficacy of these 3 types of interventions, a balanced, low-glycemic diet with a maximum of 30% fat and 15-20% protein and an emphasis on unprocessed whole grains, fruits, beans and vegetables was the most effective. This dietary intervention decreased the incidence of gestational diabetes, gestational hypertension, preterm birth, and intrauterine fetal demise (IUFD).

Dietz et al found that prepregnancy body mass index (BMI) modifies the relationship between pregnancy weight gain and newborn weight for gestational age. In a population-based cohort study of 104,980 singleton, term births from 2000-2005, women who gained 36 lb or more during pregnancy were more likely to bear an infant who was large for gestational age (birthweight >90th percentile) if the mother was lean before pregnancy than if she was overweight or obese. Compared with women who gained 15-25 lb, the adjusted odds ratio (aOR) for a gain of 26-35 lb was 1.5 (95% confidence interval [CI], 1.2-1.9); for a gain of 36-45 lb, the aOR was 2.1 (95% CI, 1.7-2.7); and for a gain of 46 lb or more, the aOR was 3.9 (95% CI, 3.0-5.0). The risk of macrosomia (birthweight 4500 g or more) was not modified by prepregnancy BMI.