Study: First trimester critical for gestational diabetes risk

LOS ANGELES - Women have long been told that gaining weight before becoming pregnant or being overweight at the start of pregnancy puts them at higher risk for gestational diabetes. But a new study finds that the first trimester is the most critical time for weight gain that can increase the danger of gestational diabetes.

The study, released yesterday in the journal Obstetrics & Gynecology, looked at data on an ethnically diverse group of women who delivered babies between 1996 and 1998; 345 women had gestational diabetes, and 800 who had not developed the disease served as a control group.

Gestational diabetes starts during pregnancy; it can disappear after giving birth but has the potential to affect mother and child for years to come.

"When we looked at weight gain by trimester, we found that association [with gestational diabetes] was mainly due to excess weight gain during the first trimester," said Monique Hedderson, the study's lead author and a scientist at the Kaiser Permanente division of research in Oakland, Calif.

During that time, women who gained more weight than is recommended by the Institute of Medicine had a 50 percent greater risk of developing gestational diabetes than those within or below the institute's recommendations.

The women in the highest category of weight gain - those who gained between 0.6 pounds and 4 pounds per week in the first trimester - had an 80 percent increased risk over women who were within or below the institute's recommendations.

The link between weight gain during the first trimester and gestational diabetes was stronger among women overweight at the start of pregnancy. Obese women (those with a body mass index of 30 or more) gained the least weight in that time, yet that group was more at risk for developing gestational diabetes.