Pre-pregnancy Lifestyle Impacts Gestational Diabetes Risk

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(Reuters Health) - A woman's pre-pregnancy lifestyle may strongly impact her risk of developing diabetes while pregnant.

Healthy eating, regular exercise, healthy weight and no history of smoking before pregnancy were each powerfully linked to whether women would develop "gestational diabetes," according to a new U.S. study.

Women with all four healthy lifestyle factors before becoming pregnant were more than 80 percent less likely to develop gestational diabetes than those with none of them, researchers found.

Maintaining a healthy body weight throughout one's reproductive life would confer the greatest benefit, said Dr. Cuilin Zhang, the study's lead author from the National Institute of Child Health and Human Development in Bethesda, Maryland. The results also highlight the potential benefit of integrating lifestyle counseling into preconception care, she told Reuters Health.

Zhang and her coauthors analyzed data on 14,437 women who participated in Nurses' Health Study II, from the time it began in 1989 to 2001, and looked at how their lifestyles related to their risk of developing diabetes during pregnancy.

Each of the individual factors was related to a lower gestational diabetes risk independently from the other three, according to Zhang. But in combinations, they were even more potent.

For instance, being a non-smoker, getting in at least 150 minutes of moderate to vigorous physical activity a week and maintaining a healthy diet was associated with a 41 percent lower risk of gestational diabetes, as compared with all other pregnancies.

"A healthful diet was one higher in intakes of vegetables, fruit, nuts, whole grains, polyunsaturated fatty acids and long chain omega-3 fatty acids and lower in intakes of red and processed meats, sugar sweetened beverages, trans fats and sodium," Zhang said.

Pre-pregnancy weight seemed to have the greatest influence, she noted. "Not being overweight or obese was related to the lowest risk of gestational diabetes as compared with other factors," said Zhang.

The researchers considered a body mass index (BMI) - a measure of weight relative to height - below 25 to be a healthy weight. But, they noted, even a pre-pregnancy BMI of 23 to 24.9, near the top of the healthy range, was linked to an elevated gestational diabetes risk.

Importantly, though, being a non-smoker, eating well and exercising were all linked to reducing the risk of diabetes, even if the women were overweight or obese before pregnancy.

If women were at a healthy weight before beginning their pregnancy, didn't smoke and were physically active, their risk was 52 percent lower compared to all other pregnancies.

Women who met the criteria for all four healthy lifestyle behaviors: a normal weight, healthy eating, exercise and no smoking were 83 percent less likely to develop gestational diabetes than those who had none of those traits and habits.

The study cannot prove that lifestyle factors do or do not cause diabetes directly because it is based only on observations, the researchers note in their report in the journal BMJ.

The results are also limited by the fact that most of the study population was white, and obesity rates were lower than in the general population, they add, so the findings may not apply more broadly.

However, the study team writes, there’s evidence that the heavy stresses on a woman's metabolism in the third trimester of pregnancy may “unmask” weaknesses in an individual’s ability to process blood sugar, so anything that predisposes a woman to diabetes before pregnancy - such as being overweight - would make her more vulnerable.

Dr. Katrien Benhalima, an endocrinologist at University Hospitals Leuven in Belgium who was not part of the study, pointed out that trying to address such health issues once a woman is pregnant is not that easy.

"Interventions to delay the development of gestational diabetes often combine weight reduction with physical activity but also physical activity alone had been associated with a lower risk," Benhalima said in an email.

She said it’s important to make these changes before becoming pregnant, as trying to make lifestyle interventions while pregnant to prevent diabetes and other potential problems is “usually disappointing.”

Another of the study’s authors, Dr. Frank Hu, of the Harvard School of Public Health in Boston, noted that planning to get pregnant offers an opportunity to improve one’s health in general. "The time before and during pregnancy may be the best opportunity to adopt a healthy diet and lifestyle because these women are particularly motivated to improve their pregnancy/birth outcomes," he said in an email.

STUDY SOURCE: BMJ, online September 30, 2014.