Fertility After Childbirth: Infant Feeding Patterns, Basal PRL Levels and Post‐partum Ovulation

Abstract

The infant feeding patterns at the time of first ovulation after childbirth were determined in a longitudinal study of twenty-seven mothers who chose to breast feed their babies. Fourteen mothers suppressed ovulation throughout lactation and thirteen ovulated while still breast feeding. Those who ovulated while breast feeding had all introduced two or more supplementary feeds/day, reduced suckling frequency to less than six times/day and reduced suckling duration to less than 60 min/day at the time of first ovulation. Basal PRL levels had fallen to below 600 microunits/l in all but one of the mothers at first ovulation. Those mothers who suppressed ovulation for more than 40 weeks post-partum (late ovulation group) were compared with those who ovulated between 30 and 40 weeks post-partum (middle group) and with those who ovulated before 30 weeks post-partum (early group). The late ovulation group breast-fed for longest, suckled most intensively, maintained night feeds for longest and introduced supplementary feeds most gradually. This study suggests suckling may be the most important factor inhibiting the return of ovulation during lactation and that policies which encourage increased suckling frequency and duration will maximize the contraceptive effects of breast feeding.

Interbirth Intervals in a Captive Group of Japanese Macaques

“…As it seems that the maternal nutritional condition affects milk production and rate of infant growth [Altmann et al, 1977;Iwamoto, 1982], it is likely that the well-nourished females of the Rome group had weaned their offspring early and suckling has been less long-lasting than in the wild. This concurs with the evidence from epidemiological and clinical studies of humans [e.g., Jain et al, 1970;McNeilly, 1979;Howie et al, 1982], These studies have indeed documented a loss of the contraceptive efficiency of breast feed ing which is associated with urbanizationi.e., with an improvement in the overall nu tritional status -and they have suggested fre quency and duration of suckling episodes to be the most important factors in inhibiting the return of ovulation during lactation. In addition, nutrition may have influenced fer tility through an increase in caloric intake and in body fat stored by females [Frish, 1978].…”

“…Pro longed lactation prevents pregnancy mainly by inhibiting the return of ovulation. In hu mans, the underlying mechanism is believed to operate through the anovulatory influence of prolactin secreted in response to the in fant's suckling [McNeilly, 1979;Howie et al, 1982], There is evidence that postpartum en docrine changes in apes and monkeys are very similar to those found in humans [Goodman and Hodgen, 1978;Nadler et al, 1981 ;Frawley et al, 1983]. Lactational infer tility appears to be a mechanism selected to achieve adequate spacing between successive births and hence to avoid maternal overbur dening.…”

Exclusive Breastfeeding and the Risk of Postpartum Relapses in Women With Multiple Sclerosis

“…5 Exclusive breastfeeding results in high prolactin levels, low and nonpulsative luteinizing hormone levels, and ovarian suppression (lack of ovulation and postmenopausal levels of estradiol and progesterone). High frequency and intense suckling maintain high prolactin levels, low luteinizing hormone levels, and lactational amenorrhea.…”

Influence of Infant Feeding Method on Postpartum Relapse of Mothers With MS

“…8 The decline in prolactin level is hastened when infant sucking at the breast is diminished by supplementation with artificial milk and/or other foods. 8 ' 9 In central Africa, where breast-feeding is sustained for two years and mothers give the breast more than six times per day, serum prolactin levels did not decline significantly during the first postpartum year. 15 The immunosuppressant effect of increased levels of prolactin may be due in part to a decreased natural killer cell activity in the presence of hyperprolactinemia.…”

“…Prolactin levels are dependent upon the interval between sucking episodes and intensity. 8 ' 9 Infant feeding by breast was coded as 0 (none), 1 (1% to 49%), 2 (50% to 79%), and 3 (80% to 100%) for each of the first six months. Codes assigned for breast-feeding at nine and 12 months were 0 (none) and 1 (some).…”