Duration of Lactation, Maternal Metabolic Profile, and Body Composition in the Norwegian EBBA I-Study

Objective There is conflicting evidence as to whether duration of lactation may decrease the risk of subsequent development of an unfavorable maternal metabolic profile including overweight and obesity. We hypothesized that duration of lactation is associated with a more favorable metabolic profile and healthier anthropometrical measurements. Methods 98 parous women from the Norwegian EBBA I-study (Energy Balance and Breast cancer Aspects-study), a cross-sectional study of healthy premenopausal women aged 25–35 years, historical lactation data were collected, anthropometrical measurements were taken, fasting blood samples (serum glucose, triglycerides, total cholesterol and HDL-cholesterol) were drawn and women were asked to fill in a pre-coded food diary. Results Mean time since last birth was 4.7 years, mean number of children was 1.9, mean total duration of lactation was 19 months and average length of lactation per child was 10.3 months. Women who on average lactated for less than 10 months per child had higher mean levels of fasting serum glucose (5.2 mmol/L vs. 5.0 mmol/L, p = 0.04), serum triglyceride (0.91 mmol/L vs. 0.66 mmol/L, p = 0.001) and serum cholesterol (4.78 mmol/L vs. 4.32 mmol/L, p = 0.004), and a higher waist-to-hip ratio (0.81 vs. 0.77, p = 0.001) than women who lactated for 10 months or more per child. The inverse association between average length of lactation per child and waist-to-hip ratio persisted after adjustment for potential confounders. Conclusions These results support the hypothesis that duration of lactation may be associated with a healthier metabolic profile and healthier anthropometrical measurements, especially lipid levels and waist-to-hip ratio even years after weanin