Results: Baseline characteristics of the study population showed no statistical differences between the groups. The median duration of
breastfeeding for both groups was 183 days. A significant BMD decrease was observed for the nonhormonal group (pb.001); however, no
statistical difference was detected for the progestin-only group. Body mass index, BMD at 7–10 days postpartum and total duration of
breastfeeding were positively correlated with BMD at 6 months.