The Contraceptive Role of Breastfeeding
This Note reviews neurohormonal mechanisms by which breastfeeding postpones the return of ovulation and menstruation after birth, and various statistical procedures used to analyze this effect in human populations. This review reveals that the biology and the statistical procedures are incompatible. The authors propose a statistical approach, compatible with present knowledge of physiology, that differentiates between ovulatory-inhibiting mechanisms at birth and the weakening of these inhibitions thereafter, so that it is possible to investigate the effects on these mechanisms due to breastfeeding and to other determinants such as mother’s age. An empirical test with typical recall data from Malaysia indicates that full breastfeeding postpones ovulation longer than does supplemented breastfeeding, and that both have stronger contraceptive effects than has been previously thought.