The recommended weight gain of 25 to 35 pounds during pregnancy can increase women's risk for giving birth to infants that are large for gestational age -- LGA -- or have excessively high birthweights -- known as macrosomia -- according to a Centers for Disease Control and Prevention study published in the July issue of the American Journal of Obstetrics and Gynecology, Reuters reports. The study also found that prepregnancy body mass index appears to affect the association between LGA and weight gain, but BMI does not affect the link between macrosomia and weight gain.

For the study, Patricia Dietz of CDC and colleagues analyzed data from the Pregnancy Risk Assessment Monitoring System on 104,980 singleton term births from 2000 to 2005. They defined LGA as greater than 90% of birthweight for gestational age and macrosomia as birthweight of at least 4,500 grams.

For women who gained 26 to 35 pounds, the risk for macrosomia increased 1.5 times relative to the risk for women who gained 15 to 25 pounds. A 36- to 45-pound weight gain increased the risk 2.1 times, while the risk increased 3.9 times for women who gained 46 pounds or more. In addition, relative to a weight gain of 15 to 25 pounds, lean women had sixfold increased risk of LGA if they gained 46 pounds or more, while obese women had a 2.4-fold increased risk for the same weight gain.

The researchers wrote, "Healthy women have been found to gain an average of 27.5 pounds. The results of our study suggest that weight above this amount may not be beneficial for the mother or the fetus, regardless of the mother's prepregnancy body mass index" (Reuters, 8/17).

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