Loss of Body Fat and Associated Decrease in Leptin in Early Lactation Are Related to Shorter Duration of Postpartum Anovulation in Healthy US Women

Abstract

Background: The mechanisms regulating postpartum anovulation (PPA) are not well understood, although poor nutritional status and “intense” breastfeeding behaviors are associated with longer durations. Objectives: This study was designed primarily to investigate the hypothesis that higher body fat and leptin concentrations are related to shorter PPA in healthy, lactating US women. Nutrient intake, breastfeeding behaviors, prolactin, and insulin levels were also evaluated. Methods: Fasting serum was collected during the third trimester of pregnancy, at 2 and 4 weeks postpartum, and every 4 weeks until the occurrence of the first postpartum menses. Body composition and breastfeeding behaviors were assessed at the same times postpartum. Women (n = 13) were categorized based on initial percentage body fat and timing of first postpartum menses. Results: There were no consistent relationships between body composition, leptin, or breastfeeding behaviors and duration of PPA. However, there was an interaction ( P = .005) between ovulation group and time on adiposity; earlier ovulating women had less percentage body fat in early lactation than did later ovulating women. There was also an interaction ( P = .1) between ovulation group and time postpartum on leptin, such that leptin concentrations tended to be greater in later than earlier ovulating groups beginning at 12 weeks postpartum. Conclusion: In summary, although baseline percentage body fat and leptin were not related to duration of PPA, fertility returned earlier in women who lost greater percentage body fat during the early postpartum period.