Washington, DC -- Women who are either underweight or overweight before getting pregnant are less likely than women of normal weight to report a target weight gain within the recommended guidelines when they become pregnant, according to a study in the March issue of Obstetrics & Gynecology.

The amount of weight a woman needs to gain during pregnancy is based on her prepregnancy body mass index (BMI), which compares weight to height. In 1990, the Institute of Medicine (IOM) issued guidelines on weight gain during pregnancy. Depending on how much a woman weighed before getting pregnant, the IOM weight gain guidelines for pregnant women are: underweight: 28-40 pounds; normal weight: 25-35 pounds; overweight: 15-25 pounds; and obese: at least 15 pounds.

Researchers examined the target weight gain (amount of weight a woman says she plans to gain) of a diverse, multiethnic group of pregnant women from the San Francisco Bay area. They also examined the amount of weight pregnant women were medically advised to gain. Researchers concluded that based on a woman's prepregnancy BMI, overweight women were more likely to have a target gain above the IOM's guidelines, and underweight women were more likely to have a target gain below the guidelines.

While a woman's prepregnancy BMI was the strongest predictor of maternal target weight gain, her health care provider's recommendation was also an important factor. Although researchers did not survey the health care providers, their findings suggest that prenatal care providers are not always following the IOM's guidelines when advising their patients, especially those women who are either over- or underweight. In the study, 33% of subjects reported receiving no advice on gestational weight gain from their provider.

Because women who gain either above or below the IOM's guidelines have higher risks for problems, including macrosomia, cesarean birth, low birth weight, and preterm birth, researchers suggest that greater public health efforts are needed to educate providers and the public about BMI-appropriate weight gain in pregnancy.

Contact: Naomi E. Stotland, MD, University of California, San Francisco, at stotlandn@obgyn.ucsf.edu.

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