It is possible to become pregnant while breastfeeding because the return of menstruation and the timing of ovulation during breastfeeding are affected by breastfeeding. In women who are not breastfeeding, ovulation usually resumes about 10 weeks after delivery, but the menstrual cycle resumes about 6-10 weeks after delivery, i.e. before ovulation. In contrast, the return of menstruation is delayed in breastfeeding mothers, and in some cases, menstruation does not occur throughout the breastfeeding period, and on average, ovulation resumes about 4-6 months after delivery. Most women who have a late return of menstruation after childbirth have ovulated before their first period, so although a breastfeeding woman does not have a period, she still has the possibility of conceiving.