Post-pregnancy, a hormone called prolactin is produced in the woman’s body after giving birth. Prolactin stimulates the production of breast milk in the body. It also suppresses the level of osterogen, causing the menstrual cycle to stop. This may last till the woman stops breastfeeding. In medical parlance, this condition is known as lactational amenorrhea.
Lactational amenorrhea is also said be a contraceptive, based on the postpartum infertility of the female body. Normally, women who are nursing at least six times during the day or are breastfeeding every four hours, and are not using any food supplements for the baby, may find that they are not menstruating and their period does not start. But periods will begin once the baby starts eating solid food or is sleeping for at least 4-6 hours in a day.
Experts say that sleeping with the newborn may also induce menstruation in some women. In this case, it is important to note that women are likely to start ovulating before the get their first period. This means that will become fertile before their first menstrual cycle after the birth of their newborn.