The return of the menstrual period after childbirth is unpredictable.

Non-nursing mothers may anticipate resumption of menses four to 12 weeks postpartum. The first period maybe irregular and heavier with associated clots. A nursing mother's menstruation usually resumes after cessation of lactation, although menstruation may begin while still breastfeeding. Lack of menses does not guarantee infertility, and adequate contraceptive measures should be taken, since a pregnancy can occur prior to the first menstrual period.