It has long been recognized that women who breastfeed their children have a longer period of amenorrhea and infertility following delivery than do those women who do not breastfeed. The length of postpartum amenorrhea is quite variable, and depends on several factors, including maternal age and parity, and the duration and frequency of breastfeeding. In general, it would appear that the more frequent and the longer the episodes of breastfeeding, the longer will be the period of anovulation, and the longer the period of infertility.
PIP: The effect of lactation on ovulation and fertility is discussed in relation to 7 factors: the duration of postpartum amenorrhea, the return of ovulation in the postpartum woman, the effect of breastfeeding on fertility, the physiologic basis for infecunity during lactation, contraceptive use during lactation (barrier methods, IUDs, and steroidal contraceptives), breastfeeding while pregnant, and tandem nursing. Women who breastfeed their children have a longer period of amenorrea and infertility following delivery than women who do not breastfeed. The length of postpartum amenorrhea varies greatly and depends on several factors, including maternal age and parity and the duration and frequency of breastfeeding. Due to the fact that there exists such individual variability in the duration of daily suckling, as well as the duration of the breastfeeding period, it is not possible to define within narrow limits the expected period of postpartum amenorrhea in lactating women. The return of menstruation is not necessarily the result of preceding ovulation in the postpartum woman. There is a wide range in the reports as to the occurrence of ovulation before 1st menstruation, ranging from 12-78%. In general, ovulation precedes 1st menstruation more frequently in those who do not nurse when compared to those who nurse. Breastfeeding has a demonstrable influence in inhibiting ovulation; it is not surprising that it has an inhibiting effect on fertility. According to Perez, during the first 3 months when a woman is nursing, there is higher security provided agaist conception than most contraceptives. After that time, the effect on fertility becomes uncertain and is determined by the frequency and duration of suckling and the time interval from delivery, and possibly maternal age, parity, nutrition. The physiologic basis for lactation infertility is not completely understood. During pregnancy, the level of circulating prolactin is greatly elevated. The elevated blood levels of prolactin begin at 8 weeks and rise to levels of 200 ng per ml at term. In lactating women, prolactin levels stay elevated, with spikes of increased secretion during and following suckling. The evideence points strongly to the fact that persistent hyperprolactinemia caused by breastfeeding postpartum results in an anovulatory or oligo-ovulatory state, and this results in relative infertility. It is appropriate to suggest other contraceptive methods to women who want to delay subsequent pregnancy because lactation alone is unreliable in preventing conception after the 9th week postpartum. There appears to be no contradindications to the use of the vaginal diaphragm or condom while breastfeeding. A report of added risk of uterine perforation in lactating women requires confirmation. The use of steroidal contraceptives while breastfeeding remains controversial.