The oxytocin and prolactin responses to suckling were measured in 10 women in early (n=5) and established lactation (n-5). Oxytocin was released in a pulsatile manner during suckling in all women, but the response was not related to milk volume, prolactin response, or parity of the mother. In all 10 women plasma oxytocin concentrations increased three to 10 minutes before suckling began. In five women this occurred in response to the baby crying, in three it coincided with the baby becoming restless in expectation of the feed, while in two it corresponded with the mother preparing for the feed. There was no prolactin response to stimuli other than stimulation of the nipple associated with suckling.These results clearly indicate that the milk ejection reflex, with release of oxytocin, occurs in most women before the tactile stimulus of suckling. A second release of oxytocin follows in response to the suckling stimulus itself. Thus it is important that care is taken to protect breast feeding mothers from stress not only during suckling but also immediately before nursing, when conditioned releases of oxytocin will occur.

Patterns of infant feeding, basal prolactin concentrations, and ovarian activity were studied longitudinally in 27 breast-feeding mothers from delivery until first ovulation.Suckling frequency (61 feeds/day) and suckling duration (122 mins/day) reached peak values four weeks post partum and remained relatively constant until the introduction of supplementary food at a mean of 16 weeks post partum. There were subsequently sharp declines in both the frequency and duration of suckling, both of which correlated closely with basal prolactin concentrations. None of the 27 mothers ovulated during unsupplemented breast-feeding, but within 16 weeks of introducing supplements ovarian follicular development had returned in 20 and ovulation in 14 mothers. The mothers who ovulated within 16 weeks of giving supplements had reduced frequency and duration of suckling more quickly and weaned more abruptly than those who continued to suppress ovulation.These data suggest that the introduction of supplementary food may exert an important and hitherto unrecognised effect on the timing of first ovulation by reducing the frequency and duration of suckling episodes.

SUMMARY The resumption of post‐partum menstruation and ovulation was studied in ten bottle feeding and twenty‐seven breast feeding mothers. First menstruation occurred at 8±1 weeks (± 1±0 SE) in bottle feeders and 32±5 weeks (±2±5 SE) in breast feeders (P < 0±001); first ovulation occurred at 10±8 weeks (±1±0 SE) in bottle feeders and 36±4 weeks (±2±5 SE) in breast feeders (P < 0±001). In bottle feeders, ovulation preceded first menses in only 2/10 (20%) of mothers but was regularly established thereafter, occurring in 17/18 (94%) of second and subsequent cycles. Breast feeding did not postpone ovulation indefinitely because 13/27 of the breast feeding mothers ovulated while still lactating; ovulation occurred in 9/27 (33%) of breast feeding mothers during the phase of lactational amenorrhoea but was followed by menstruation in every case. In breast feeding mothers, the frequency of ovular cycles progressively increased with time, ovulation being observed in 9/20 (45%) of first cycles during lactation, 20/30 (66%) of later cycles during lactation, 16/23 (70%) of first cycles after lactation and 26/31 (84%) of later cycles after lactation. There was a disruption of menstrual rhythms during lactation, the mean interval between the first day of consecutive menstrual cycles being 37±0 days ± 3±3 SE during lactation compared with 29±8 days ± 1±0 SE after lactation and 29±5 days ± 1±0 SE in the bottle feeding mothers. This study shows that bottle feeding is associated with an early resumption of post‐partum menstruation and ovulation. In breast feeding mothers, there is complete suppression of ovulation during the greater part of lactational amenorrhoea but ovulation will return in a proportion of mothers just before first menses. After the return of menstruation during lactation, the frequency of ovular cycles progressively increases but does not return to normal until complete weaning has taken place.

The PRL response to suckling was studied during the first week of the puerperium. Mean basal levels of PRL showed no significant changing during the first week of the puerperium, but there were progressive rises in both the maximum suckling-induced response and the total area under the response curve, which reached peak values on the fourth day after delivery. Despite large variations between individuals in basal PRL levels (range, 0.3-7.0 U/liter), peak suckling-induced response (range, 0.1-9.9 U/liter), and total response (range, 0.6-63.0 arbitrary units), there was much less variability within individuals between consecutive feeds. Using an electronic balance, 20 patients on days 5 and 6 were classified either as good feeders (greater than 60 g milk/feed) or poor feeders (less than or equal to 60 g milk/feed) on the basis of 2 consecutive test weights. The mean PRL response to suckling in 11 good feeders was no different from that in 9 poor feeders, and there was no significant correlation between milk yield and PRL response. Six patients whose infants were in the special care nursery had lactation initiated and maintained by breast pump for an average of 5.6 days. Although the PRL response to the breast pump was very small, these patients also had satisfactory milk yields (mean, 86 g). Although the presence of PRL is essential for lactation, the data in this paper suggest that there is no close temporal correlation between PRL concentrations and milk yield.

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.

During studies on the resumption of fertility postpartum in 12 breast feeding mothers who were using no contraception, eight pregnancies occurred. In seven cases these pregnancies occurred while the mothers continued to breast feed while in one it occurred within 2 weeks of weaning. In two cases pregnancy occurred prior to first postpartum menstruation but followed an abrupt decline in suckling frequency and duration resulting in resumption of follicular development and ovulation. In the remaining six cases, pregnancy was preceded by between 1 and 7 menstrual cycles, the majority of which (13/19) had deficient luteal phases or were anovular (4/19). In all mothers a significant decrease in the suckling frequency and duration observed during lactational amenorrhoea had occurred prior to the resumption of ovulation and conception. No mother conceived with a suckling frequency of greater than three times per day although some mothers ovulated without conceiving when suckling four times per day. The results suggests that if a breast feeding mother wishes to rely upon the infertility associated with lactational amenorrhoea, she must suckle at least five times per day with a total suckling duration of more than 65 min per day (more than 10 min per feed). Any reduction below either of these limits may result in a return of fertility.

No abstract

Awareness of the important role of breast feeding in child health and the reproductive cycle, which is well documented elsewhere, necessitates an examination of the changing practice of breast feeding. This paper reviews these changing practices both in Western and developing societies, examines the problems which lead to lactation failure, and looks at factors related to success in breast feeding. In the light of the need for practical help for successful breast feeding. the present system of support both in hospital and at home is then discussed. An alternative system of structured home support for post-natal women, which has been shown to increase the success rate of breast feeding, is outlined. The way in which this system acts is discussed and the implications for both mothers and health staff are considered.