How Much Weight Gain is Optimal During Pregnancy?

(This is a review of 3 separate studies, done by the editors of 'Journal Watch', Nov. 2007)

The weight of women of reproductive age is increasing in the U.S. In three separate studies, researchers addressed the vexing question of whether recommendations for optimal weight gain during pregnancy should vary depending on prepregancy body-mass index (BMI)

Two studies used data from the Missouri birth registry. In the first study, investigators evaluated women with normal prepregnancy BMIs. Compared with women who gained 25 to 35 pounds during pregnancy, those who gained less than 25 pounds had lower odds for pre-eclampsia, cephalopelvic disproportion, failed induction of labour, caesarean delivery, and large-for-gestational-age infants and had higher odds for small-for-gestational-age infants. Women who gained more than 35 pounds (43% of the study population) had increased odds for preeclampsia, cephalopelvic disproportion, failed induction, caesarean delivery, and large-for-gestational-age infants, and had lower odds for small-for-gestational-age infants.

In the second study, researchers evaluated overweight and obese women. Compared with weight gain during pregnancy of 15 to 25 pounds, gain of less than 15 pounds was associated with lower risk of preeclampsia, caesarean delivery, and large-for-gestational-age infants and higher risk for small-for-gestational-age infants and higher risk for small-for-gestational -age infants. Of note, among the obese women (BMI more than 30), 23% gained less than 15 pounds, and 46% gained more than 25 pounds during their pregnancies.

In a third study, from Sweden, researchers found that optimal weight gain during pregnancy was less than 13 pounds for prepregnancy BMI more than 30, less than 20 pounds for a BMI 25 to 29.9, and less than 22 pounds for women in all categories of BMI less than 24.9

Thus: Pregnancy weight gain of more than 35 pounds, regardless of prepregnancy weight, is associated with higher risk for adverse outcomes. Lower weight gain among over weight women seems to be associated with lower risk for adverse maternal and obstetric outcomes.