WEDNESDAY, March 18, 2015 (HealthDay News) -- Obese women who develop diabetes during pregnancy, and then gain 11 pounds or more after giving birth, have more than a 40 times higher risk of developing type 2 diabetes, a new study suggests.
Diabetes that develops during pregnancy is known as gestational diabetes. While this type of diabetes often disappears after pregnancy, it's long been known that women who've had the condition have a higher risk of developing type 2 diabetes later in life. Background information in the new study pointed out that as many as one-third of women with type 2 diabetes had a history of gestational diabetes.
Excess weight is a risk factor for both gestational and type 2 diabetes, according to the researchers.
"Our findings show the importance of maintaining a healthy body weight both before and after pregnancy," said lead researcher Dr. Cuilin Zhang, a senior investigator in the epidemiology branch at the U.S. National Institute of Child Health and Human Development.
"Women should strive to maintain a healthy body weight over their lives to lower the risk of diabetes," Zhang added.
The report was published March 18 in the journal Diabetologia.
Dr. Mitchell Roslin, chief of obesity surgery at Lenox Hill Hospital in New York City, said that type 2 diabetes is not a sudden occurrence, but develops over time.
"It's probably a 15-year process that begins with insulin resistance as cells in the pancreas start working less," he said. "When a woman has gestational diabetes, it's telling you that they are already on the pathway to diabetes, and even a small amount of weight gain can put them over the edge."
Roslin said the most common patient he sees is a woman who gains weight during and after several pregnancies. "It becomes a vicious circle," he said.
The only way for these women to prevent or delay developing type 2 diabetes is to lose weight and exercise, Roslin suggested. "Exercise is tremendously important," he said. "There is a huge link between exercise and improvement in insulin resistance."
For the study, Zhang and colleagues collected data on nearly 1,700 women who took part in the Diabetes & Women's Health Study and developed gestational diabetes between 1991 and 2001.
The researchers found that over 18 years of follow-up, 259 of the women developed type 2 diabetes. The risk of type 2 diabetes increased by 27 percent for each 11 pounds a woman gained after having gestational diabetes -- no matter what her pre-pregnancy weight, the researchers said.
But, for women who were already obese when they developed gestational diabetes, gaining 11 pounds or more was associated with a 43 times higher risk of developing type 2 diabetes, compared to women who were not obese and gained fewer than 11 pounds after having gestational diabetes, Zhang's group found.
The risk for developing type 2 diabetes persisted even after taking into account factors such as age, a family history of diabetes, diet, physical activity, breast-feeding and the time since pregnancy, the study authors found.
A recent study in the April issue of the journal Obstetrics & Gynecology reported that nearly half of all pregnant women gain more weight than recommended during pregnancy.
"This is a concern because gaining too much weight has health consequences for both mothers and infants," said one of that study's co-authors, Andrea Sharma, an epidemiologist with the U.S. Centers for Disease Control and Prevention's Maternal and Infant Health Branch.
During pregnancy, women who are at a normal weight at the beginning of their pregnancy should generally gain about 25 to 35 pounds, according to guidelines from the Institute of Medicine (IOM). Women who are underweight when pregnancy begins should aim for 28 to 40 pounds, and it's recommended that women who are obese at the start of pregnancy keep weight gain to 11 to 20 pounds, according to the IOM.
Some excess weight gain might result from misconceptions, said Dr. Karen Cooper, an obstetrician/gynecologist and director of the Cleveland Clinic's Be Well Moms program.
"Most women feel that pregnancy is the time when weight does not matter and it is an opportunity to eat as much as desired," said Cooper, who was not involved with the new study. "Most believe the myth that the weight will be lost quickly and easily after delivery."
For more on type 2 diabetes, visit the American Diabetes Association.