Effects of breast feeding after resumption of menstruation on waiting time to next conception

We investigate the association between breast feeding after resumption of menstruation and the duration from resumption of menses to the next conception. Data from a survey, "Breast-Feeding and Its Effect on Fertility," conducted in 1987 under the auspices of the Centre of Population Studies, Banaras Hindu University, India, were used. We used hazard models of conception rates after the return of menstruation with breast-feeding duration as a time-dependent covariate. The interaction of breast-feeding duration after resumption of menses and postpartum amenorrhea have a significant effect on the rate of conception after return of menses. After resumption of menstruation, when there is no breast feeding, the risk of conception increases with the increase in postpartum amenorrhea. However, breast feeding attenuates the effects of postpartum amenorrhea. These results suggest that breast feeding beyond the resumption of menstruation plays a significant role in the proximate determinants to reduce fertility.