(Reuters Health) - Women who gain substantial amounts of weight after their first pregnancy may be more likely to develop gestational diabetes during their next pregnancy, a Norwegian study suggests.

Gestational diabetes is a form of glucose intolerance that develops for the first time during pregnancy. The condition is more common among women who are overweight or obese when they become pregnant or who gain a lot of weight during pregnancy.

“It is important to prevent gestational diabetes as it is associated with complications in mothers and babies during birth, and health care costs in mothers with gestational diabetes are 25 percent higher compared to non-diabetic mothers,” said lead study author Linn Marie Sorbye, a midwife and public health researcher at the University of Bergen in Norway.

For the current study, researchers examined data on 24,198 mothers in Norway with a first and second pregnancy between 2006 and 2014.

Compared to women whose weight didn’t fluctuate much after the first pregnancy, women whose body mass index (BMI) - a ratio of weight to height – rose significantly were between twice and more than five times as likely to develop gestational diabetes during their second pregnancy, the study found.

Overall, there were 18 cases of gestational diabetes for every 1,000 second pregnancies, researchers report in PLOS Medicine.

The focus on promoting healthy weight in the reproductive population needs to be expanded to include preconception throughout reproduction, Sorbye said by email.

Women who are underweight at the start of pregnancy should gain 28 to 40 pounds, while women who are normal weight are advised to gain 25 to 35 pounds, according to the U.S. Institute of Medicine. For overweight women, a 15- to 25-pound gain is recommended and obese women should gain just 11 to 20 pounds.

For a nonpregnant adult who is 5 feet 9 inches tall, gaining just ten pounds is more than enough to go up more than one BMI unit, the threshold in the study for an increased risk of gestational diabetes.

Slightly more than one third of the women in the study gained more than one BMI unit of weight between the start of their first pregnancy and the start of their second pregnancy. This included women who didn’t lose all of the weight after the first baby arrived as well as women who gained extra pounds between pregnancies.

Women who gained up to two BMI units of weight between pregnancies had a doubled risk of gestational diabetes compared to women who gained no more than one BMI unit, the study found. Women who gained four BMI units, meanwhile, had a five-fold increased risk of gestational diabetes.

A BMI calculator is available for free online from the National Institutes of Health, at bit.ly/2tXeEf4.

The study wasn’t a controlled experiment designed to prove how or if a failure to lose baby weight or a gain of extra pounds between pregnancies causes gestational diabetes.

“Further research is needed to tease out exactly how changes in weight, particularly over short time interpregnancy intervals, have adverse metabolic effects in future pregnancies,” Dr. Jacinda Nicklas, a researcher at the University of Colorado School of Medicine who wasn’t involved in the study said by email.

Shorter periods between pregnancies may not give women enough time to lose weight and increase their risk of gestational diabetes the second time around, said Dr. Sharleen O’Reilly a researcher at University College Dublin in Ireland.

“Weight loss should be a mix of healthy eating and more physical activity, and we know that both together are more effective in helping women lose weight after pregnancy,” O’Reilly said by email.

SOURCE: bit.ly/2vllnDk PLOS Medicine, online August 1, 2017.