BREASTFEEDING - NATURE'S WAY OF SPACING BABIES? The fertility regulating effect of breastfeeding has been known for underestimated. This has been due mostly to the lack of knowledge of the events associated with breastfeeding that determine its contraceptive effect. It is now known that breastfeeding per se is not a particularly effective or reliable means of contraception. On the other hand, the period of amenorrhea associated with breastfeeding, commonly referred to as lactional amenorrhea, provides an important degree of contraceptive effect.Physiology of Contraceptive Effect of Breast Feedingh Endocrine Responses to Breastfeeding The physiological response to suckling at the breast is not local, but is mediated hormonally through afferent neural signals to the brain from receptors in the nipple. The secretion of two pituitary hormones, oxytocin and prolactin, into the circulatory system, marks the mother's primary response to suckling. Leake et al. reported the continued presence of a vigorous oxytocin response in long-term (up to one year) breastfeeding. Oxytocin is secreted from specialised nerve endings in the posterior pituitary and participates in the milk ejection reflex, while prolactin is secreted from cells within the anterior pituitary and appears to be responsible for the co-ordination of the complex biochemical processes involved in milk production. No reports were found that might attribute to oxytocin an ability to interact with the reproductive system. In contrast to the apparent lack of interaction of oxytocin, prolactin may affect reproduction at multiple sites including the hypothalamus, the pituitary and the ovaries. However it is not clear to what extent that any direct effects of prolactin are responsible for fertility suppression during lactation. Gross and Eastman have developed a model of serum prolactin concentration during lactional amenorrhea, derived from data acquired from a...
