We found that adequate breastfeeding (≥6 breast milk–months) was associated with lower BMI, waist circumference, and SAT levels in a multiethnic population of youth 6–13 years of age from Colorado. Moreover, our study provides novel evidence that the effect of exposure to diabetes in utero on childhood adiposity parameters is substantially attenuated by breastfeeding, such that the obesity outcomes in exposed youth who were adequately breast-fed were similar to those of unexposed youth. Our data suggest that breastfeeding promotion may be an effective strategy for reducing the increased risk of childhood obesity in the offspring of mothers with diabetes during pregnancy.
The current literature on the impact of breastfeeding for the offspring of diabetic women is inconclusive. Plagemann et al. (18
) suggested an adverse effect of breastfeeding during the first 7 days of life on relative weight at 2 years of age among offspring of women with type 1 diabetes and GDM. However, a follow-up of this study was conducted by Rodekamp et al. (19
) with an extended assessment of breastfeeding exposure beyond the first week of life. The researchers found that neither dose of breast milk nor duration of breastfeeding among offspring of type 1 diabetic women was associated with increased risk of overweight or impaired glucose tolerance at 2 years of age. In another study, Kerssen et al. (20
) showed no effect of breast milk, formula, or mixed feeding on the weight or BMI of offspring exposed to type 1 diabetes during pregnancy at 1 year of age. In contrast, among 15,253 offspring of the 1989 Nurses’ Health Study II, Mayer-Davis et al. (21
) reported a protective OR of 0.63 (95% CI 0.50–0.78) for overweight at 12 years of age for breastfeeding duration of ≥9 versus <9 months. OR for overweight among offspring exposed to GDM in utero who were exclusively breast-fed compared with those exclusively formula-fed was 0.62 (0.24–1.60). Among Pima Indians, Pettitt and Knowler (22
) found a substantial reduction (30.1 vs. 43.6%) in type 2 diabetes among the offspring exposed to diabetes in utero if they were breast-fed for at least 2 months compared with those who were bottle-fed. A similar reduction was observed among Pima offspring not exposed to in utero diabetes (6.9 and 11.9% among offspring of nondiabetic women who were breast-fed and bottle-fed, respectively).
The early postnatal period may represent a critical period for the future obesity risk in childhood (23
) and adult life (6
). The macronutrient composition of breast milk (i.e., protein, fat, carbohydrate) and bioactive substances not present in formula may influence metabolic programming and regulation of body fatness and growth rate. Higher insulin levels (24
) and lower leptin levels (25
) have been reported in formula-fed infants compared with breast-fed babies. The effect of breastfeeding on infant growth may be an important determinant of early life programming for future obesity and chronic disease, especially for the offspring of diabetic pregnancies.
Our study adds to the limited body of evidence by suggesting that breastfeeding attenuates the unfavorable effects on childhood adiposity parameters conferred by exposure to maternal diabetes. Importantly, all measures of adiposity were influenced including the more sensitive VAT and SAT. The mechanisms that trigger adipose tissue deposition in specific locations at different periods of fetal development or in childhood remain unclear. Identification of strategies to alter the long-term development of fat deposition and accumulation are necessary to minimize the significant increased morbidity risk associated with childhood obesity. Fetal life and early infancy both represent critical periods when obesity begins and may be effectively minimized by targeted prevention strategies.
Our study had some limitations. An a priori power calculation suggested that, with 100 exposed individuals, our study had 80% power to detect a difference in the effect of exposure to diabetes in utero on childhood BMI according to breastfeeding status (an interaction) of 0.4 BMI units. The observed difference in our study was 0.5 BMI units; however, the difference was not statistically significant, possibly because of the slightly smaller achieved sample of exposed individuals. This suggests that we had limited power to detect a statistically significant effect of breastfeeding in modifying the association between exposure to diabetes in utero and childhood adiposity. Nevertheless, our findings of an attenuation of the effect of in utero exposure on childhood adiposity by breastfeeding was robust and consistent across various measures of adiposity including BMI, waist circumference, SAT, VAT, and fat distribution. Similar effects were noted regardless of how our breastfeeding variable was defined (i.e., breastfeeding yes/no, duration in months, etc.; data not shown). Moreover, our study had several important strengths including state-of-the-art assessment of childhood adiposity and fat distribution, a validated exposure assessment, and an assessment of breast milk dose that incorporated breastfeeding exclusivity and duration.
In conclusion, our study found no deleterious effects of breastfeeding among a diverse group of children exposed to diabetes in utero. In contrast, we suggest that breastfeeding may be protective against the increased childhood adiposity associated with intrauterine diabetes exposure. Further work is needed to confirm this finding in larger populations, and to determine if the reductions in adiposity continue into adulthood.