Recently published: Three studies advance gestational diabetes research

Researchers at the Division of Research have conducted recently published observational research that underscores the importance of reducing the risk of diabetes during pregnancy — also called gestational diabetes (GDM).

GDM, glucose intolerance that typically occurs during the second or third trimester of pregnancy, complicates between 7 and 14 percent of United States pregnancies and can lead to delivery complications as well as long-term health risks for baby and mother, explain the researchers.

More specifically, GDM is associated with an increased risk of cesarean section and may increase the baby and the mother’s risk of developing diabetes, obesity or metabolic disease later in life.

A Woman’s Risk of GDM May Be Identifiable Long Before Pregnancy
A study led by Monique Hedderson, PhD, suggests that whether a woman will develop GDM during pregnancy may actually be predicted years before she becomes pregnant — by assessing routine measures of blood sugar and body weight.

In the study published in May online in the American Journal of Obstetrics and Gynecology, Hedderson and her Division colleagues explored these measures among women examined during multiphasic health checkups between 1984 and 1996. The study looked at cardio-metabolic risk factors routinely measured before pregnancy in women who later became pregnant.

The research provides evidence to support preconception care for healthy pregnancies as suggested by the Centers for Disease Control and Prevention (CDC) in a 2006 report on the subject. The CDC report suggests that risk factors for adverse pregnancy outcomes can be identified  prior to conception and emphasizes a need for the initiation of interventions prior to conception.

The Hedderson study found that the risk of GDM increased in conjunction with risk factors commonly associated with diabetes and heart disease. Women in the study with increased BMI and blood sugar levels had a 4.6-fold increased risk of GDM compared to women with normal BMI and blood sugar levels.

“It’s important to recognize that women who develop GDM are at increased risk of developing type 2 diabetes, a chronic condition that these relatively young women may have to manage for the rest of their lives,” added Samantha Ehrlich, MPH, a U.C. Berkeley PhD candidate. Ehrlich led a related study that looked at how weight gain between the first and second pregnancies impacts the risk of developing GDM in a second pregnancy.

Weight loss between pregnancies reduces GDM risk
Compared with women whose weight remained stable, women with body mass index (BMI) gains between their first and second pregnancies had an increased risk of GDM in their second pregnancy, according to the Ehrlich-led study that appeared online in May in Obstetrics and Gynecology.

Results of that study are the first to show that women who lose weight between their first and second pregnancies may reduce the GDM risk in their second pregnancy, particularly if they were overweight or obese to begin with.

The study examined a diverse cohort of 22,351 women from Kaiser Permanente in Northern California over a 10-year period. Women who gained 2.0 to 2.9 BMI units — approximately 12 to 17 pounds — between their first and second pregnancies, were more than twice as likely to develop GDM in their second pregnancy compared to those whose weight remained stable, plus or minus approximately six pounds.

Women who gained three or more BMI units — approximately 18 or more pounds — between their first and second pregnancies were more than three times as likely to develop GDM during their second pregnancy compared to those whose weight remained stable.

By contrast, women who lost more than six pounds between their first and second pregnancies reduced their risk of developing GDM in their second pregnancy by about 50 percent compared to women whose weight remained stable. The association between losing weight and reduced GDM risk was strongest in women who were overweight or obese during their first pregnancy, explained the researchers.

There is strong evidence from previous efficacy trials in at-risk populations that type 2 diabetes can be prevented through lifestyle interventions that focus on weight management, emphasized Ehrlich, explaining why a recently launched Division intervention study is critical to better understanding what helps women lose weight after a GDM pregnancy.

Lifestyle intervention may help women lose weight after a GDM pregnancy
A feasibility intervention study, led by Assiamira Ferrara, MD, PhD, was completed and published online in May in Diabetes Care. A team of 10 Division investigators, led by Ferrara, is now undertaking a randomized comparative effectiveness study to see if a telephone intervention after a GDM pregnancy is more effective — than recommendations of diet and physical activity sent by mail — in helping  new moms lose weight and reduce their risk of developing diabetes.

The results of the feasibility intervention study among women with gestational diabetes show that in women with gestational diabetes, a lifestyle intervention — including modified diet and physical activity that starts during pregnancy and continues postpartum — is feasible and may prevent diabetes by reducing pregnancy weight retention. The intervention can also help overweight women lose weight, according to the published results.

This study represents the first lifestyle intervention for diabetes prevention starting during pregnancy and continuing postpartum that has been translated for use in women with GDM, explained Ferrara.

“Starting an intervention soon after diagnosis of GDM is important because evidence shows that women who exceed Institute of Medicine guidelines during pregnancy retain twice as much weight compared to women who gain weight within the recommendations,” she said, explaining that this weight retention is associated with an increased likelihood of long-term obesity.

“A lifestyle intervention that starts soon after the diagnosis of GDM takes advantage of the teachable moment of pregnancy, because women with GDM are concerned about their children’s increased risk of adverse health outcomes as well as their own increased risk of diabetes, which can motivate the adoption of preventive behaviors.”

Study participants were recruited between October 2005 and June 2009. The intervention used in the study — called Diet, Exercise and Breastfeeding Intervention (DEBI) — was delivered over the phone by trained dieticians and included three phases: prenatal, postpartum and maintenance. About 200 women with GDM participated in the study.

The larger comparative effectiveness study of diabetes prevention strategies in women with GDM is now underway and has been described in a previous Research Spotlight article.

The investigators have also established a GDM registry within Kaiser Permanente Northern California. This registry, started in 1995, is one of the first GDM registries and includes more than 30,000 women with at least one pregnancy complicated by GDM. It has been a unique resource for epidemiologic, health services and comparative effectiveness research, said Ferrara.

Previously published Division research on gestational diabetes
See links below for a press release about each published paper.

• A study in the American Journal of Epidemiology found that cardio-metabolic risk factors such as high blood sugar and insulin, and low high density lipoprotein cholesterol that are present before pregnancy, predict whether a woman will develop diabetes during a future pregnancy.
• A study in Obstetrics and Gynecology showed that pregnancy weight gain, especially in the first trimester, may increase a woman’s risk of gestational diabetes
• A study in The Journal of the American Diabetes Association showed that breastfeeding a child may protect women from metabolic syndrome, a condition linked to diabetes and heart disease in women.
• A study in Obstetrics and Gynecology showed that gestational diabetes increased 35 percent between 1991 and 2000.
• A study in Obstetrics & Gynecology showed that women who gain excessive weight during pregnancy, especially in the first trimester, may increase their risk of developing diabetes later in their pregnancy. A video of Monique Hedderson, PhD, the study’s principal investigator, may be seen below.