Breastfeeding has numerous immediate health benefits for both mothers and infants. Emerging evidence reveals possible long-term benefits including lower risk of cardiometabolic diseases even among high risk women with gestational diabetes mellitus (GDM) and their offspring. In cross-sectional studies, lactating compared with non-lactating women with recent GDM had more favorable metabolic profiles (lower fasting glucose and triglycerides, higher disposition index), and lower prevalence of diabetes during the early postpartum period.1;2 Breastfeeding intensity appears to be particularly important; exclusive or mostly breastfeeding (0 to 6 oz formula/day) groups have better postpartum glucose tolerance than exclusive or mostly formula feeding groups, but mixed/inconsistent feeders do not.3 Findings lactation lower risk of incident type 2 diabetes after GDM pregnancy are conflicting, with one study showing a 50% reduction in risk and another reporting a null association.4;5 However, lack of data on postpartum lifestyle behaviors and self-report of diabetes remain significant limitations of these studies.4;5 A 20-year prospective study of U.S. women of reproductive age (CARDIA Study) measured cardiometabolic risk factors from before to after pregnancy at 2-5 year intervals, and reported that longer duration of lactation (>2-5 mos to >9 mos vs. 0 to <1 mos) was associated with a 2- to 7-fold lower incidence rate of the metabolic syndrome adjusted for parity, BMI, lifestyle behaviors and weight gain.6 Findings were similar for women without GDM and those with GDM.
Breastfeeding also has been associated with a 22 to 24% lower risk of overweight, but primarily in Caucasian children and adolescents from developed countries. Yet, evidence is mixed as to whether breastfeeding confers the same protection against overweight to the offspring exposed to diabetes in utero. These offspring are more vulnerable to obesity, cardiometabolic disease and diabetes, but few prospective studies have assessed the impact of breastfeeding on their risk of overweight or metabolic disease. Retrospective studies provide evidence that breastfeeding “adequately” may lessen child adiposity or risk of diabetes for offspring of mothers with diabetes. However, most of these studies examine breastfeeding retrospectively, and cannot distinguish mixed feeding from exclusive breastfeeding. Emerging evidence supports the hypothesis that higher breastfeeding intensity by mothers with GDM slows infant growth during the first year of life .
Prospective studies in Northern California are underway to assess whether higher intensity and longer duration of lactation prevent or delay the development of type 2 diabetes and pre-diabetes (standardized annual OGTT screening) during the two years after delivery among women with recent GDM pregnancies, and whether breastfeeding slows weight gain during early life in their offspring. The Study of Women, Infant Feeding, and Type 2 Diabetes (SWIFT) is comprised of 1,035 postpartum women with recent GDM (multi-racial/ethnic cohort; 75% minority) who delivered in the Kaiser Permanente Health Care system from 2008-2011, and were enrolled at 6-9 weeks postpartum.7 SWIFT prospectively assesses breastfeeding intensity and duration during the first year postpartum. In the SWIFT Offspring Study, we assess growth in 470 of their infants during the first year of life. Our preliminary findings support the hypothesis that breastfeeding has long-term health benefits among women with a history of GDM and their infants. The SWIFT cohort consists of 25% White, 8% Black, 32% Asian, including East and Southeast Asians, and 32% Hispanic women. Intensively breastfeeding and Intensively formula feeding groups had similar glucose intolerance during pregnancy, and gestational weight gain, and family history of diabetes. The formula feeding group had lower educational attainment and has greater proportion of obese women. The SWIFT Study’s initial findings indicate that lactation may lower the risk of incident type 2 diabetes in women, contribute to greater postpartum maternal weight loss, and slow the growth of their offspring from 3-6 months of age. Long-term follow up of the SWIFT cohort is underway.
National Institutes of Health, National Institute of Child Health and Human Development, Bethesda, Maryland, United States; R01 HD050625, R01 HD050625-03S1, The Centers for Disease Control and Prevention, The American Diabetes Association and Kaiser Permanente Northern California.