Diet, exercise and weight control counseling in early pregnancy can lower the risk of developing diabetes before giving birth, according to a new study from Finland.

"Gestational diabetes and maternal obesity are both independently associated with adverse maternal and neonatal outcomes," and many women who have gestational diabetes develop type 2 diabetes within 10 years, said lead author Dr. Saila B. Koivusalo of Helsinki University Hospital and Katiloopisto Maternity Hospital.

Between 2 and 18 percent of pregnancies involve gestational diabetes, Koivusalo told Reuters Health by email.

Women who do not have diabetes before getting pregnant may develop it during pregnancy, especially if they have risk factors like being overweight, or they had gestational diabetes in a past pregnancy. The condition can be managed during pregnancy and often goes away afterward, according to the Centers for Disease Control and Prevention.

To see if it can be avoided entirely, even by women with heightened risk, the researchers recruited 293 women who were less than five months into their pregnancies and either had a history of gestational diabetes or were obese, but did not have type 1 or 2 diabetes.

The women were randomly divided into two groups, with half the women receiving only standard prenatal care.

In the intervention group, however, the women received one-on-one counseling on diet, physical activity and weight control with trained nurses as well as one group meeting with a dietitian.

Obese women were advised to avoid any weight gain during the first two trimesters. Dietary counseling focused on optimizing the amount of vegetables, fruits and berries, whole grains, low-fat dairy, unsaturated fatty acids, fish and lean meats in the diet, and reducing sugar intake.

For physical activity, the women aimed to get a minimum of 150 min of moderate-intensity physical activity each week. They also had free access to public swimming pools and guided exercise groups once a week.

Close to 14 percent of the women in the counseling group developed gestational diabetes, compared to almost 22 percent of the standard-care group, after the researchers accounted for age and prepregnancy weight, according to the report in Diabetes Care.

That represents a 39 percent risk reduction in this group of high-risk women, the authors note.

Women in the counseling group tended to gain less weight during pregnancy, about 1.3 pounds less than those in the comparison group. They also increased their physical activity and improved their diet quality compared to the other group.

"This is a very nice trial that demonstrates that small changes in eating habits and physical activity patterns may have an important impact in women at risk for gestational diabetes," said Dr. Kaberi Dasgupta of McGill University in Montreal.

"What is remarkable is that the occurrence of (gestational diabetes) was reduced by a relatively simple intervention with only three in-person sessions," Dasgupta, who was not part of the study, told Reuters Health by email. "There may also be a 'healthier culture' in Scandinavian countries that makes people more responsive to health behavior change interventions."

Since this is the first randomized controlled trial to test lifestyle interventions for preventing gestational diabetes, it's still unclear when is the best time in pregnancy to start making changes to reduce risk, Koivusalo said.

"Taken together, prevention of overweight and obesity already before the first pregnancy is an important factor when aiming at optimal maternal and neonatal outcomes," she said. "And weight control should also continue after pregnancy when the maintenance of a healthy lifestyle among children also needs to be stressed."

Most women can make healthier lifestyle choices on their own, she said. "But it may be important to have a support person during the process of lifestyle changes, as we know that they are not necessarily easy to carry out," she said.

In the Finnish study, the study nurses were midwives with strong expertise in counseling pregnant women, she noted.