Breastfeeding and return to ovulation in Bangkok.

Twenty-seven breastfeeding mothers and nine non-breastfeeding postpartum comparison mothers in Bangkok, Thailand were followed longitudinally until ovulation resumed. A simple set of guidelines is described involving three obvious milestones for the breastfeeding mother to safely use the natural contraceptive benefit of breastfeeding. Those milestones are the first menses, the initiation of supplementation and the child's monthly birthday. In the absence of menses and supplementation, 93% of breastfeeding mothers remained anovular for 3 months postpartum and 88-89% for up to 6 months. Further, the work of other investigators suggests that the proportion ovulatory provides an overestimate of those at risk of pregnancy. The guidelines suggest a way to estimate the period of lactational infertility and may be most useful on a programmatic level.