The author reports on studies of the relationship between breast-feeding and fertility in Pakistan, the Philippines, and Thailand. "The accumulated evidence suggests that during the first six months of unsupplemented breast-feeding, if the mother remains amenorrheic, then the breast-feeding stimulus is usually sufficient to postpone the recovery of fertility. Breast-feeding frequency alone is not a useful measure of the breast-feeding stimulus in terms of its ability to predict the return of menses or ovulation."
PIP: In the past decade, many studies on breastfeeding (BF) and the return of "fertility" (fecundity) have been conducted. 3 recent prospective studies suggest that individual variations in the response to the BF stimulus make it difficult to predict when fertility will return if only 1 parameter is used as a predictor. The accumulated evidence suggests that if the mother remains amenorrheic, then the BF stimulus is usually sufficient to postpone the recovery of fertility. BF frequency alone is not a useful measure of the BF stimulus in terms of its ability to predict the return of menses or ovulation. In all 3 studies, pregnancy and vaginal bleeding were the outcome variables indicating fertility. In Bangkok, Thailand, ovarian hormones were measured so that ovulation could be detected. BF frequency was measured in all 3 studies to quantify the BF stimulus. A longitudinal study was conducted in Karachi, Pakistan. 28 normal parturient who planned to breastfeed and not practice hormonal contraception were followed-up weekly for 1 year unless they got pregnant earlier. They were asked about the occurrence of vaginal bleeding and contraception. The average (median) time until the 1st postpartum bleeding episode (the proxy for fertility), was 4.6 months (mean=5.9 months). The time of the 1st bleeding ranged from 2 to more than 12 months after birth. A study done in Bangkok used the same study design as was used in Pakistan, but measured the occurrence of ovulation. A 12-hour overnight urine sample was collected twice a week. It was assayed for pregnanediol-3-2-glucuronide, a metabolite of progesterone. Progesterone is produced by ovulation. 19 mothers who were BF their babies varied largely in BF frequency and the duration of anovulation. The Bangkok study agrees with the conclusions in the Karachi study about BF, but uses a more precise measure of the dependent variable. In a study in the Philippines, the independent variable (BF) was manipulated to see if a change in the response (menses) could be brought about. 2 comparable rural setting were chosen; 1 experimental; the other, control. A BF education program was done in the experimental community. Mothers in both groups had their 1st period at the same rate frequency (12-13 times/day). BF frequency was not increased in the 1st 5 months postpartum. This study is being replicated in an urban area of the Philippines.