The return of fertility and normal menstrual periods for individual women after having a baby varies widely. However, it is important to remember that it is possible for a woman to be fertile again and conceive a subsequent baby after 4 weeks of giving birth.
While there are many individual factors that can affect a woman's return to fertility, women who breastfeed are more likely to delay their ability to conceive again. However, breastfeeding (as an only form of contraception) tends to be only reliable for about 30% of breastfeeding women. (If your baby is less than 6 months old, you are fully breastfeeding day and night without the baby having any other food or fluids and you have not had a period since the bleeding has stopped after the birth, then your chances of becoming pregnant again are thought to be about 2 to 3 %. However, not all women will have all these things happening, therefore the general advice is not to rely totally on breastfeeding for contraception.)
Women who breastfeed may not have a normal menstrual period until their baby is fully weaned off the breast (perhaps 9 to12 months or more). Other women will start to experience periods again once their baby starts on solids at around 4 to 6 months, (or if they start complementing their baby's breastfeeds with formula milk). A few women will experience 'light periods' of pink, or light red bleeding, for a day or so every month, at sporadic and unpredictable times. Occasionally, the woman will experience normal periods each month, even though she is fully breastfeeding.