Breastfeeding suppresses fertility for a variable length of time, but when certain criteria are applied, it can be a reliable contraceptive. The individual variation in duration of infertility is directly related to suckling activity. As suckling declines, follicle growth resumes and ovulation may occur. Infertility is maintained by suckling-induced disruption of the normal pattern of pulsatile luteinizing hormone release and is related to an increased sensitivity of the hypothalamus to the negative feedback effects of oestradiol. Even if ovulation does resume, the corpus luteum function is often insufficient to maintain pregnancy. Attempts to alter suckling activity to prolong lactational infertility are not successful, but maintenance of reasonable suckling frequencies of normal duration can protect women from pregnancy for a prolonged period postpartum.
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