A breastfeeding woman may become pregnant even if she is not menstruating. Because of the high level of prolactin during breastfeeding, ovulation may be inhibited and there is usually no resumption of menstruation when there is no ovulation. When the number of breastfeeding decreases for some reason, the lactogen in the body decreases and there is a gradual decrease in milk, at which time the inhibition of ovulation by lactogen is also reduced and ovarian function may resume at that time and the ovaries resume ovulation. After ovulation, if there is no conception, menstruation will occur. Therefore, a lactating woman who ovulates more irregularly before the onset of menstruation and who has sex without effective contraception may become pregnant. Therefore, effective contraception should be used to avoid unwanted pregnancies during breastfeeding, even if you do not have a period. Condoms or intrauterine devices can be used. The use of birth control pills is not recommended to avoid interfering with breastfeeding.