December 7, 2015

Breastfeeding may help prevent type 2 diabetes after gestational diabetes

At a Glance

  • Among women who had gestational diabetes, breastfeeding was associated with a lower rate of type 2 diabetes for up to 2 years after childbirth.
  • The results suggest that breastfeeding after gestational diabetes may have lasting effects that reduce a woman’s chance of developing type 2 diabetes.
Woman with newborn. In addition to healthy eating and physical activity, breastfeeding may also help women who’ve had gestational diabetes prevent or delay type 2 diabetes. NiDerLander/iStock/Thinkstock

About 5-9% of pregnant women nationwide develop high blood sugar levels even though they didn’t have diabetes before pregnancy. This condition, called gestational diabetes, drastically raises a woman’s risk for type 2 diabetes later in life. In type 2 diabetes, cells don’t respond properly to insulin, a hormone that signals cells to take in the sugar glucose from the blood. If left untreated, blood sugar levels can soar and cause a host of health problems, including heart disease, stroke, kidney disease, blindness, and amputation.

Research has found that breastfeeding increases insulin sensitivity and improves glucose metabolism in the mother. However, studies have been inconclusive as to whether breastfeeding lowers the risk of type 2 diabetes, particularly among women with a history of gestational diabetes. A research team led by Dr. Erica P. Gunderson at the Kaiser Permanente Division of Research set out to address the question. Their work was funded by NIH’s National Institute of Child Health and Human Development (NICHD) and others.

The team enrolled more than 1,000 ethnically diverse women (75% minority) who were diagnosed with gestational diabetes. Trained research staff assessed the women’s lactation intensity and duration using feeding diaries, telephone calls, in-person examinations, and monthly mailed questionnaires. The researchers tested for glucose tolerance 6 to 9 weeks after delivery and then annually for 2 years. Results appeared online on November 24, 2015, in Annals of Internal Medicine.

During the 2-year follow-up, 113 of the 1,010 women without diabetes at the study baseline (11.8%) developed type 2 diabetes. After accounting for differences in age, pre-pregnancy body size, and other risk factors, the researchers estimated that women who exclusively breastfed or mostly breastfed were about half as likely to develop type 2 diabetes as those who didn’t breastfeed.

How long women breastfed also affected their chance of developing type 2 diabetes. Breastfeeding for longer than 2 months lowered the risk of type 2 diabetes by almost one half, the researchers calculated. Breastfeeding beyond 5 months lowered the risk by more than one half. Notably, differences in weight loss, which affects type 2 diabetes risk, didn’t account for these risk differences.

“Both the level and duration of breastfeeding may offer unique benefits to women during the post-delivery period for protection against development of type 2 diabetes after gestational diabetes,” Gunderson says.

Longer follow-up will be needed to determine how long the benefits of breastfeeding might last and to understand the underlying biological mechanisms.

—by Harrison Wein, Ph.D.

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Reference: Lactation and Progression to Type 2 Diabetes Mellitus After Gestational Diabetes Mellitus: A Prospective Cohort Study. Gunderson EP, Hurston SR, Ning X, Lo JC, Crites Y, Walton D, Dewey KG, Azevedo RA, Young S, Fox G, Elmasian CC, Salvador N, Lum M, Sternfeld B, Quesenberry CP Jr; Study of Women, Infant Feeding and Type 2 Diabetes After GDM Pregnancy Investigators. Ann Intern Med. 2015 Nov 24:889-898. doi: 10.7326/M15-0807. [Epub ahead of print]. PMID: 26595611.

Funding: NIH’s National Institute of Child Health and Human Development (NICHD) and National Center for Research Resources (NCRR); Kaiser Permanente Northern California Community Benefit Program; and W.K. Kellogg Foundation.