is moderate in humans. In non-breast-feeding women, the menstrual cycle may return within 1 month after delivery, whereas fully lactating women have a period of several months of lactational amenorrhea, with the first few menstrual cycles being anovulatory. The cessation of cyclicity results from the combined effects of the act of suckling and elevated PRL levels. PRL suppresses ovulation by inhibiting pulsatile GnRH release, suppressing pituitary responsiveness to GnRH, reducing LH and FSH, and decreasing ovarian activity. It is also possible that PRL may inhibit the action of the low circulating levels of gonadotropins on ovarian cells. Thus, follicular development would be suppressed by a direct inhibitory action of PRL on the ovary. Although fertility is reduced by lactation, there are numerous other methods of contraception (see Clinical Focus Box 39.3).
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For many years, scientists have been playing out the ingredients that make breast milk the perfect food for babies. They've discovered to day over 200 close compounds to fight infection, help the immune system mature, aid in digestion, and support brain growth - nature made properties that science simply cannot copy. The important long term benefits of breast feeding include reduced risk of asthma, allergies, obesity, and some forms of childhood cancer. The more that scientists continue to learn, the better breast milk looks.