After giving birth to a baby five months did not come to menstruation, may include the following reasons: 1, normal phenomenon: after giving birth to a baby five months did not come to menstruation, it is not necessarily an abnormal phenomenon, because after giving birth to a baby, especially within six months, regardless of whether there is breastfeeding, the probability of restoring ovulation is not very high, so the menstruation did not come normally is also a normal phenomenon, especially breastfeeding women, exclusively breastfeeding women breastfeeding This is a normal phenomenon, postpartum breastfeeding women, some times even a year or two years without normal menstruation. 2, pregnant again: if women have sex after childbirth, without good contraceptive measures, need to exclude the case of pregnancy again, generally more than 12 days after the last intercourse can use a pregnancy test 3, delivery factors: If there is placenta or fetal membrane residue during delivery, as well as heavy bleeding during delivery or postpartum hemorrhage, it may affect the recovery of the uterus, affect the endometrial proliferation, as well as affect ovulation, resulting in menstruation has not been able to come, this situation may need to be combined with B ultrasound or hysteroscopy Ultrasound or hysteroscopy may be required to confirm the diagnosis.