Breastfeeding can be done without menstrual flow and normally, if the mother does not resume ovulation, then she will not become pregnant. During breastfeeding, the hormones in the mother’s body differ from those of a normal woman. In order to meet the purpose of producing milk during lactation, the level of lactogen is increased in the pregnant woman’s body. In the presence of lactogen, most women have no menstrual flow. However, there are some women who resume their normal menstrual cycle during breastfeeding. It is important to note that the resumption of menstrual cycle is not absolutely related to ovulation. Most women who have not resumed their menstrual cycle do not ovulate and therefore cannot become pregnant when they have sex during this period. However, there are still some women who have not resumed their menstrual cycle, but have ovulation from the ovaries. Therefore, if ovarian ovulation occurs during the breastfeeding period when menstruation has not yet resumed, it may result in another pregnancy. Therefore, it is recommended that if a woman does not want to have a baby anytime soon, she should use appropriate contraception during breastfeeding. Condoms are generally the best method of contraception. As mentioned above, some women may still be pregnant during the breastfeeding period when they have not yet resumed their menstrual cycle, so it is important to use proper contraception.