Breastfeeding does not have to stop in order to concieve, however breastfeeding does lower the body's production of oestrogen. Oestrogen is needed to have normal ovulation and periods. Whether a mother breastfeeds or not, if she has her first period within six months of delivery, she has a 67 percent chance that it is anovular. There can be a lag of just under 16 weeks between menses first reappearing, and an egg being produced at the same time.
After the first six months from delivery, the chances of experiencing anovular periods, drops to 22 percent. Breastfeeding influences the continued absence of periods after birth. Some women use this phenomenon as a means of contraception. It is an unreliable method, unless the woman knows how to monitor her body closely and does so diligently. For most women, it is impossible to tell when the first ovular cycle begins and she is potentially fertile again. If your periods have returned and are regular then it is likely that breastfeeding is no longer affecting your fertility.