Excess weight gain, especially in the first trimester, increased gestational diabetes risk by about 50% among the women included in the study.
And overweight women who gained the most weight in their first and second trimesters were twice as likely to develop gestational diabetes later in pregnancy as overweight women who gained the least weight.
Obesity is a well-known risk factor for gestational diabetes, which occurs in up to 7% of pregnancies in the U.S.
But the study is among the first to link weight gain early in pregnancy to gestational diabetes.
The study was conducted by the research arm of the California-based managed care group Kaiser Permanente. It appears in the March issue of Obstetrics & Gynecology.
"There has been a dramatic rise in gestational diabetes within the past decade," study researcher Monique M. Hedderson, PhD, tells WebMD. "Women who develop gestational diabetes are more likely to have preterm deliveries and C-sections. And even after delivery they are at increased risk for developing type 2 diabetes."
Babies born to women with gestational diabetes also have an increased risk for obesity and diabetes during childhood.
Minority Women Most at Risk
The three-year study included 1,145 women living in northern California who were followed throughout their pregnancies.
Weight gains were measured in the first trimester and again prior to screening for gestational diabetes, which typically occurred in the 24th to 28th week of pregnancy.
Actual weight gains were compared to recommended weight gains published by the health policy group the Institute of Medicine (IOM) in May of last year.
These guidelines call for weight gains of between 1.1 pounds and 4.4 pounds in the first trimester of pregnancy, regardless of weight at the beginning of pregnancy.
According to the IOM, normal-weight women should gain between 25 and 35 pounds during pregnancy, while overweight women should gain 15 to 25 pounds and obese women should gain 11 to 20 pounds.
After adjusting for well-known risk factors for gestational diabetes, including obesity and older age, women who gained the most weight prior to diabetes screening were 74% more likely to develop gestational diabetes than women who gained the least
The risk associated with early pregnancy weight gain seemed to be higher for black, Hispanic, and Asian women than for white women.
Non-white women in the study who gained the most weight early in pregnancy had a 2.5-fold increased risk for developing gestational diabetes, compared to a 1.5-fold increase in risk among white women.
Tips for Healthy Weight Gain
Kaiser Permanente ob-gyn Amanda W. Calhoun, MD, who practices in Richmond, Calif., tells WebMD the new research will definitely influence how she advises patients about early pregnancy weight gain.
Calhoun is the co-author of the 2009 book My Pregnancy Pocket Guide.
"We've been focused on total weight gain during pregnancy, but not so much on weight gain early in pregnancy," she says. "This information about the impact of weight gain in the first trimester is really brand new."
She adds that nutritional counseling early in pregnancy could have a big impact on increasing gestational diabetes rates.
Among her tips for controlling weight gain during pregnancy:
- Eat regular meals and small, healthy snacks between meals. This will also help control pregnancy-related nausea.
- Cut down on sweets and sweetened drinks.
- Eat only about 100 to 300 extra calories a day.
- Reduce fat intake to less than 30% of calories.
She also recommends 30 minutes of exercise on most days of the week. Women who already exercise should continue, but decrease the intensity of their workouts by about 15%. Women who don't exercise should talk to their health care provider about starting a program