Lactation and fertility.
In almost all mammals lactation, or more correctly the suckling stimulus, induces a period of infertility designed to provide the optimal birth spacing for survival of the offspring. The duration of lactational infertility depends on the sucking activity of the young with little evidence to support a role for nutritional status. Suckling disrupts the normal pulsatile pattern of hypothalamic gonadotrophin releasing hormone (GnRH)2 secretion resulting in reduced LH secretion from the pituitary. Secretion of FSH returns to its normal cyclic pattern early in lactation and ovarian follicles may develop under its influence. However, until suckling declines, the follicles fail to secrete amounts of estradiol adequate to stimulate an LH surge and ovulation. The suckling stimulus may affect GnRH secretion by affecting prolactin, opiate and dopaminergic tone in the hypothalamus but no unifying mechanism has yet been proposed convincingly. The birth spacing effects of breastfeeding in women have a profound effect on infant well-being, and breastfeeding still prevents more pregnancies than all forms of artificial contraception.
McNeilly
A S
AS
MRC Reproductive Biology Unit, Edinburgh, Scotland, United Kingdom. a.mcneilly@ed-rbu.mrc.ac.uk
D000818:Animals; D001721:Birth Intervals; D001940:Breast / Q000502:physiology; D001942:Breast Feeding; D004298:Dopamine / Q000502:physiology; D004971:Estrus / Q000502:physiology; D005193:Family Planning Services; D005260:Female; D005298:Fertility / Q000502:physiology*; D005640:Follicle Stimulating Hormone / Q000378:metabolism; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology; D007223:Infant; D007231:Infant, Newborn; D007774:Lactation / Q000502:physiology*; D007986:Luteinizing Hormone / Q000378:metabolism; D008322:Mammals / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000502:physiology; D008597:Menstrual Cycle / Q000502:physiology; D012252:Natural Family Planning Methods; D010053:Ovary / Q000502:physiology; D010060:Ovulation / Q000502:physiology; D010903:Pituitary Gland, Anterior / Q000378:metabolism; D011247:Pregnancy; D011388:Prolactin / Q000502:physiology; D012636:Secretory Rate; D013045:Species Specificity
D007987:Gonadotropin-Releasing Hormone; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D004298:Dopamine