Pregnancy Lifestyle Influences Gestational Diabetes Risk

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Meredith Carlson-Daly: Nearly half of all cases of diabetes during pregnancy could be prevented if the expecting mothers ate well, exercised regularly, stopped smoking, and maintained a healthy body weight before pregnancy, a new study finds.

Diabetes during pregnancy—also known as gestational diabetes—is a common pregnancy complication that can have long-term health effects for both mothers and babies. For example, affected babies are more likely to be born abnormally large and with birth defects. They are also at greater risk for childhood obesity and for Type 2 diabetes later in life.

The study appeared in the British Medical Journal and was funded in part by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. The researchers found numerous links between the unhealthy habits and diabetes during pregnancy. One of the key findings was that the women with the highest risk were overweight or obese before pregnancy.

From the National Institutes of Health, I’m Meredith Carlson Daly and this is Research Developments, a podcast of the NICHD. With me today is the study’s lead author, Cuilin Zhang, of the Institute’s Epidemiology Branch, Division of Intramural Population Health Research.

Thank you for joining us today, Dr. Zhang.

Dr. Cuilin Zhang: Sure, my pleasure. Thanks for having me Meredith.

Ms. Carlson-Daly: Dr. Zhang, I wonder if you could start off by defining gestational diabetes. What is it and how would a pregnant woman know if she had it?

Dr. Zhang: Sure, I’d be happy to. Gestational diabetes is high blood sugar with onset or first diagnosed during pregnancy. Our body uses glucose for energy. But, too much glucose in pregnant women’s blood is not good for either women or their babies.

Usually women are tested for gestational diabetes between weeks 24 and 28 of pregnancy by measuring their blood glucose levels. If women have a higher chance of getting gestational diabetes, for instance they are obese before pregnancy; doctor may test for diabetes during their first perinatal visit.

Ms. Carlson-Daly: And how common is gestational diabetes?

Dr. Zhang: Well, this really depends on the diagnosis criteria used. There are still debates regarding the best diagnosis criteria. I am not getting into that today. In the United States, gestational diabetes affects roughly between 1 % and 26% of all pregnancies. And this pregnancy complication is a growing health concern; multiple population-based studies have shown increases in its occurrence in the past decade.

Ms. Carlson-Daly: What did your study find?

Dr. Zhang: So, in this study, we found that low risk lifestyle before pregnancy (that is, maintaining a healthy body weight, consuming a healthy diet, exercising regularly (at least 150 minutes a week, and not smoking) was related to a substantially lower risk of gestational diabetes. And women at low risk for all these four factors had more than 80% lower risk than those without any of these low risk factors.

We also found that the combination of the four highest risks: smoking, inactivity, overweight or obesity and poor diet could account for nearly half of gestational diabetes events.

And, importantly, among both normal weight and obese or overweight women, a healthy diet and lifestyle was related to a lower risk.

Ms. Carlson-Daly: So, let me see, I’m just going to repeat back. Let me just see if I have this correctly because it seems to be a very important finding. So, women who had the four factors: smoking, inactivity, being overweight or obese before becoming pregnant, and a poor diet. All those four categories, the women who did not have those were 80% less likely to have gestational diabetes?

Dr. Zhang: That is right, exactly.

Ms. Carlson-Daly: That is an enormous statistic.

Dr. Zhang: It is! It is amazing, but if you look at our paper you can see woman who can really fit into that category, really healthy diet and lifestyle, the number is so small. Even among these women who are health professionals. So, this on the other hand also indicates we have lots of space for intervention.

Ms. Carlson-Daly: Can you tell me what the findings mean for women who are pregnant or who are planning a pregnancy?

Dr. Zhang: So, clearly, women who are pregnant or planning a pregnancy should stop smoking, adopt a healthy diet, and get regular exercise. And if overweight or obese before pregnant, they should take steps to lower their weight.

And as we know, obesity has become a global epidemic, and its prevalence continues to increase, unfortunately. And women of reproductive age are no exception. A high proportion of women, more than 40%, are overweight or obese when they become pregnant.

And we all know it is so hard to lose weight. And the promising news from the present study is that, even for overweight or obese women, stopping smoking, adopting a healthy diet, and getting regular exercise were related to a great decrease in the risk of developing diabetes in pregnancy.

And another question is whether to encourage all women planning pregnancy to adopt these healthier lifestyles, or to limit our attempts only to those presently at higher risk. I would agree with the editorial in the British Medical Journal strongly encouraging all women planning a pregnancy, including those at low risk, to eat better, stop smoking, and exercise more.

Ms. Carlson-Daly: I mean, you know, you can’t go wrong even if you are starting out healthy, to maintain those four key factors.

Dr. Zhang: Yes, that’s true. Exactly!

Ms. Carlson-Daly: How did you select the women you studied?

Dr. Zhang: Well, our study are based on a comprehensive investigation of more than 14,000 healthy women in the United States who took part in the Nurses' Health Study II between 1989 and 2001. And as some of you may know, the Nurses’ Health Study II, is an ongoing prospective cohort that was established in 1989 by enrolling more than 100,000 female nurses aged 24-44 years old at baseline from the United States.

Ms. Carlson-Daly: How did you collect the data on the women’s smoking, their diet, their exercise?

Dr. Zhang: So in this study, we obtained the information of women’s’ smoking and weight every two years. And beginning in 1991 and every four years thereafter, women were asked to complete a food frequency questionnaire in addition to the main questionnaire. And as some of you may know diet, the food frequency questionnaire was designed to measure average habitual dietary intakes over a year-long period.

And physical activity, exercise was assessed on the main questionnaire in 1989, 1991, and 1997. Women were asked to report the average amount of time they spent on moderate or vigorous recreational activities each week.

Ms. Carlson-Daly: Where does this research go from here?

Dr. Zhang: This is really a good question. So, thinking about the future research along this line, one feature of the present study was that women were predominantly white and all were nurses. So, it would be really important for future research to find out whether lifestyle changes would have the same effect in other ethnic groups or in populations who aren’t as well-educated about health and wellness as the nurses in our study.

And secondly, our promising findings are based on an observational study. So, an intervention study among women who are planning pregnancy on the impact of promoting healthy diet and lifestyle before pregnancy in lowering GDM risk and improving maternal and neonatal outcomes may also be warranted.

And if we can prevent gestational diabetes at the first beginning, it could be an important strategy in curbing its related adverse health events for future generations.

And in addition, going beyond pregnancy, we all know that women who have gestational diabetes are at exceptionally high risk for developing type 2 diabetes later in their lives and their children may be at greater risk for obesity and cardio-metabolic disorders. But, indeed, very limited is known about determinants of these subsequent adverse health outcomes among women and their children, and about how to prevent these adverse events. And we do not know well about the underlying mechanisms either.

So, in the Division of Intramural Population Health Research, we are trying to answer these questions in the ongoing Diabetes & Women’s Health study and a planning study on the trans-generational impact of diabetes in pregnancy. Fortunately, we have identified some promising findings. And hopefully, in the near future we’ll have more findings to share.

Ms. Carlson-Daly: Thank you so much. This is Research Developments, a podcast of the Eunice Kennedy Shriver National Institute of Child Health and Human Development. I’ve been speaking with Cuilin Zhang, lead author of the study about risk factors for gestational diabetes, published in the British Medical Journal. Thanks again for joining us today, Dr. Zhang.

Dr. Zhang: Sure, my pleasure. Thank you again for having me.

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About the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute's website at http://www.nichd.nih.gov/.