Nearly every woman frets about gaining weight after giving birth. But after your first baby is born, you can increase your chances of a subsequent healthy pregnancy by keeping your weight the same or less.

Women who gain weight, even seven pounds, after their first pregnancy raise their risk of suffering high blood pressure, diabetes and stillbirth during the second pregnancy.

For example, a 5-foot-5 woman who weighs 139 pounds before her first pregnancy would have a healthy "body mass index." If she gained just seven pounds before her second pregnancy, her index would still be healthy, but her risk of becoming diabetic in the second pregnancy would rise 30 percent.

If she gained 12.2 pounds, her risk would increase 100 percent.

"It turns out that women do not need to become overweight or obese to increase their chances of having poor gestational outcomes," said Dr. Eduardo Villamor, a nutrition expert at the Harvard School of Public Health. "One message could be that women should not gain any weight. They should try to go back to their pre-pregnant weight and should not gain any weight after the first pregnancy.

"Obviously, overweight and obese women should try to reduce their weight, and that's likely accompanied by other health benefits."

Double-digit risk increases

The findings present a new angle to America's growing problem with expanding waistlines. In 2000, nearly 30 percent of the women 20 to 39 - the prime child-bearing years - suffered from obesity, compared to only 9 percent in 1962.

Villamor and Sven Cnattingius, a researcher with Stockholm's Karolinska Institute, reached their conclusions after studying more than 150,000 Swedish women who gave birth to their first and second children between 1992 and 2001.

In their project, Villamor and Cnattingius based their findings on a woman's "body mass index," the ratio of weight to height that many health experts use to judge whether a person is overweight or obese.

The reseachers found:

•  The more weight the women gained between births, the more at risk they were for pre-eclampsia, high blood pressure, diabetes, Caesarean section, still-birth and delivery of large babies.

•  Even a gain of one to two BMI units boosted the odds of diabetes and high blood pressure during pregnancy by 20 to 40 percent. One BMI unit equals about 6.6 pounds.

•  A woman who gained three or more BMI units risks a 63-percent greater risk of a stillbirth compared to women who gained less than one BMI, according to the results.

•   If women lowered their weight, the risks decreased.

Numerous studies throughout the years have linked obesity to pregnancy complications, but the new study sheds light on a direct cause-and-effect relationship.

Dr. Aaron Caughey, an assistant professor of obstetrics and gynecology at the University of California, San Francisco, said one factor in a woman's weight gain after pregnancy could be breastfeeding.

In an editorial accompanying the study, Caughey said women who breastfeed gain less weight after birth and  breastfeeding for longer periods of time lowers the risk of diabetes.

The study appears in the recent The Lancet, a British medical journal.

In-vitro problems

But another new study about pregnancy and complications showed that women who exercised for at least four hours a week were 40 percent less likely than sedentary women to have a live birth after their first cycle of in-vitro fertilization.

In-vitro fertilization is the process by which a woman's eggs are fertilized outside her body and then surgically implanted back into her uterus. Infants born by this method are commonly referred to as "test-tube babies."

The study by researchers at Brigham and Women's Hospital in Boston found that women who exercised regularly were twice as likely to have an implantation failure or pregnancy loss after undergoing in-vitro fertilization.

The research linked cardiovascular exercise to a 30-percent lower risk of a successful live birth. The scientists said they are not sure why exercise brought about the negative effects, although hormones may play a part.

The study appears in October's Obstetrics & Gynecology.

This article includes information from HealthDay.

Source: Harvard School of Public Health
References: The Lancet

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