OAKLAND, Calif., November 23, 2015 -- Women with gestational diabetes who consistently and continuously breastfeed from the time of giving birth are half as likely to develop type 2 diabetes within two years after delivery, according to a study from Kaiser Permanente published today in Annals of Internal Medicine.
Gestational diabetes mellitus, or high blood glucose during pregnancy, is diagnosed in 5 percent to 9 percent of all pregnancies in the United States -- approximately 250,000 women annually. Women with gestational diabetes are up to seven times more likely to develop type 2 diabetes within several years after pregnancy. Breastfeeding is recommended for women with GDM, but previous studies exploring the impact of breastfeeding on subsequent development of diabetes have had inconsistent findings.
In this study, women who exclusively or mostly breastfed for at least two months after giving birth, and those who continued to breastfeed for several months, were able to cut their risk for type 2 diabetes by half.
"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 pregnancy," said lead author Erica P. Gunderson, PhD, MPH, MS, epidemiologist and senior research scientist at the Kaiser Permanente Division of Research.
The "Study of Women, Infant Feeding and Type 2 Diabetes after GDM Pregnancy," also known as the SWIFT Study, is the first to measure breastfeeding on a monthly basis during the first year after delivery and to enroll a statistically significant number of women with gestational diabetes. It is also the first to evaluate social, behavioral and prenatal risk factors that influence development of type 2 diabetes, as well as breastfeeding initiation and success.
The study enrolled more than 1,000 Kaiser Permanente members in Northern California who were diagnosed with gestational diabetes during pregnancy between 2008 and 2011. The SWIFT cohort was racially and ethnically diverse, with 75 percent of the women reporting Hispanic, Asian or African-American heritage. In-person exams, which included oral glucose tolerance tests, were conducted at six to nine weeks after delivery as women enrolled in the study, and again at one year and two years post-delivery in those who did not have diabetes at baseline.
Almost 12 percent of women in the study developed type 2 diabetes within two years after delivery. Those who exclusively formula-fed their babies at six to nine weeks of age were more than twice as likely to develop diabetes as women who exclusively breastfed their infants. There was a graded 35 percent to 57 percent reduction in the two-year diabetes incidence associated with greater lactation intensity -- from exclusively formula-feeding to exclusively breastfeeding, and with increasing lactation duration -- from less than two months to more than 10 months of breastfeeding.
A major strength of the study was the ability to control for numerous influences on breastfeeding and other diabetes risk factors, including maternal obesity before pregnancy, gestational weight gain, prenatal metabolism, treatment for gestational diabetes, C-section delivery, infant size and birth outcomes, race/ethnicity, and lifestyle behaviors such as diet, physical activity and weight change. The association between breastfeeding intensity and duration with lower risk of developing type 2 diabetes remained after accounting for these variables.
"These findings highlight the importance of prioritizing breastfeeding education and support for women with gestational diabetes as part of early diabetes prevention efforts by health care systems," Dr. Gunderson concluded.
Co-authors of the study were Shanta R. Hurston, MPA, Xian Ning, MS, Joan C. Lo, MD, Barbara Sternfeld, PhD, and Charles P. Quesenberry, Jr., PhD, of the Kaiser Permanente Northern California Division of Research; Yvonne Crites, MD, David Walton, MD, Robert A. Azevedo, MD, Stephen Young, MD, Gary Fox, MD, Cathie C. Elmasian, MD, Nora Salvador, MD, and Michael Lum, MD, of The Permanente Medical Group; and Kathryn G. Dewey, PhD, of the Department of Nutrition, University of California, Davis.
Primary funding for the study was the National Institute of Child Health and Human Development (R01 HD050625, Dr. Gunderson). Other sources included the Kaiser Permanente Community Benefit Program, the W.K. Kellogg Foundation, and the National Institutes of Health National Center for Research Resources.
About the Kaiser Permanente Division of Research
The Kaiser Permanente Division of Research conducts, publishes, and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR's 500-plus staff is working on more than 400 epidemiological and health services research projects. For more information, visit http://www.dor.kaiser.org or follow us @KPDOR.
About Kaiser Permanente
Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America's leading health care providers and not-for-profit health plans. Founded in 1945, Kaiser Permanente has a mission to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 10 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/share.
Annals of Internal Medicine