First trimester weight gain & diabetes risk

Women who gain weight too quickly during the first three months of pregnancy are more prone to develop pregnancy-related diabetes, known as gestational diabetes.

Gestational diabetes occurs when a woman's pancreas can no longer keep up with the body's growing demands for the blood-sugar-regulating hormone insulin. Left untreated, high blood sugar in pregnancy can cause the fetus to grow abnormally large, increasing the risk of injury to baby and mother during delivery. While a woman's glucose (sugar) metabolism usually returns to normal after her pregnancy is over, she runs a higher risk of developing type 2 diabetes later on.

Women typically undergo an oral glucose tolerance test between the 24th and 28th weeks of pregnancy to assess whether their body is producing enough insulin. To date, only few studies have looked at the rate of weight gain before this test and gestational diabetes risk.

To investigate this, researchers in the U.S. compared 345 women who developed gestational diabetes to 800 women who did not, all of whom delivered their babies between 1996 and 1998 and had oral glucose tolerance tests at 24 to 28 weeks' gestation.

After adjusting for age at delivery, race/ethnicity, the number of previous pregnancies, and prepregnancy body mass index, the researchers found that women who gained weight the most slowly during their first trimester (less than a third of a kilogram per week, or just over half a pound) had the lowest risk of gestational diabetes. Risk went up as a woman's rate of first trimester weight gain increased; for women gaining between 0.3 and 0.4 kilograms (0.6 to 0.9 pounds), diabetes risk was about 40 percent higher; for women who gained more than 0.4 kilograms (0.9 pounds), risk increased 74 percent.

This study suggests that weight gain in early pregnancy may be a modifiable risk factor for pregnancy-related or gestational diabetes.