FERTILITY AFTER CHILDBIRTH: CHANGES IN SERUM GONADOTROPHIN LEVELS IN BOTTLE AND BREAST FEEDING WOMEN

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Abstract
Changes in basal serum gonadotropin levels during the resumption of ovarian activity postpartum were studied longitudinally in breast- and bottle-feeding mothers. On the basis of urinary steroid levels, ovarian activity was classified as showing complete suppression, follicular activity only, deficient luteal phases or normal menstrual cycles. Complete suppression of ovarian activity during lactation was associated with normal levels of FSH but low levels of LH [luteinizing hormone]. The resumption of follicular development was not accompanied by any increase in levels of either LH or FSH when compared with the phase of complete suppression, and this pattern persisted during menstrual cycles characterized by deficient luteal phase progesterone secretion. Basal LH levels did not rise to normal levels during lactation until the resumption of normal ovulatory cycles. FSH secretion remained at a level comparable with the follicular phase of normal ovulatory cycles throughout the postpartum period. In mothers who did not breast-feed, LH levels rose more rapidly than in breast-feeding mothers and had returned to within normal limits by 3 wk postpartum. At 4 wk postpartum FSH levels were lower in bottle-feeding mothers than in breast feeders probably in response to the early rise in estrogen levels among bottle feeders. Apparently, decreased LH but not FSH secretion may be important in maintaining infertility associated with breast-feeding. The absence of any change in LH or FSH at the onset of follicular development suggests that an alteration in the sensitivity of the ovary to gonadotropins or in the pattern of gonadotropin secretion may be involved in the observed patterns of postpartum ovarian activity during lactation.