Weight Gain May Endanger Pregnancy

Gaining even a modest amount of weight between pregnancies could lead to serious complications in childbirth, according to a new report from the Harvard School of Public Health (HSPH).

The study, published in the Sept. 30 issue of the British medical journal The Lancet, examined a population of more than 150,000 Swedish women who had their first and second births between 1992 and 2001. Researchers found that women who gained weight between pregnancies were at a higher risk of adverse outcomes such as gestational diabetes, gestational hypertension, and stillbirth.

“It turns out that women do not need to become overweight or obese in order to increase their chances of having poor gestational outcomes,” said Assistant Professor of International Nutrition Eduardo Villamor, one of the study’s lead researchers. “A relatively modest increase in weight between pregnancies could lead to serious illnesses.”

The researchers calculated body mass index (BMI), which is a measurement based on weight and height, at the first prenatal visit for each of the consecutive pregnancies. They compared increases in BMI with the frequency of complications in the second pregnancy.

Results showed that a gain of only one or two BMI units—equivalent to about 6.6 pounds for a woman who weighs 139 pounds and is five feet five inches tall—increased the risk of gestational diabetes and gestational hypertension by an average of 20 to 40 percent.

A gain of three of more BMI units increased the chances of stillbirth by 64 percent and increased the chances of all other complications.

The findings suggest that obese women should lose weight if they want to reduce their risk of pregnancy complications, Villamor said.

The study was limited in that it did not differentiate between weight gained as a result of the initial pregnancy and weight gained following childbirth. Researchers also admitted that other factors could be associated with both weight gain and pregnancy complications, but said they were confident in their findings, according to a HSPH press release.

“A key public health message from our study is that women of normal weight should avoid gaining weight between pregnancies,” Villamor said. “In addition, overweight and obese women are likely to benefit from weight loss if they are planning to become pregnant.”

The study was a joint effort between the Harvard School of Public Health and Karolinska Institutet in Stockholm, Sweden.