Fertility of fully breast-feeding women in the early postpartum period

To examine bleeding between 6 and 8 weeks postpartum in fully breast-feeding women and its association with fertility as assessed by hormone analysis.

Seventy-two fully breast-feeding women were followed prospectively from 42 days postpartum. Vaginal bleeding was recorded daily. Women who experienced bleeding were compared with women who did not with respect to time of ovulation and time of first menses.

Nearly half of the women experienced some vaginal bleeding or spotting between 6 and 8 weeks postpartum. These women eventually menstruated and ovulated earlier than the women who did not bleed, but the differences were not significant. The study had 34% and 45% power to detect a 20% difference in the proportion menstruating and ovulating, respectively, at 6 months postpartum, and 10% and 16% power to detect the same differences at 1 year. Seven women experienced ovarian follicular development before day 56, but neither bleeding nor follicular development was associated with ovulation in any woman in the first 8 weeks postpartum.

It is unlikely that vaginal bleeding in fully breast-feeding women in the first 8 weeks postpartum represents a return to fertility.