Effects of lactation, contraception and other factors on birth interval in Bangladesh : evidence from the 1989 BFS

Birth interval is an important index that reflects the level of fertility and its changes. While married and fecund, women reproduce at a rate inversely related to the average duration of the birth interval, short birth intervals are associated with high fertility and vice versa. In the absence of intrauterine mortality, the length of birth interval is determined by its three components: the postpartum infecundable interval, the waiting time to conception and a full-term pregnancy. Demographic analyses have demonstrated that in populations without access to modern forms of contraception, birth intervals are determined principally by the duration of breastfeeding(Bongaarts and Potter, 1983). The purpose of this paper is to examine the relationship of postpartum practices such as breastfeeding and use of contraception to birth intervals by taking them as intermediate variables. For the present study we will concentrate our analysis on the last closed birth interval, which is the interval between the penultimate and ultimate child. Accordingly, the objectives of this study are: (1) To determine the main determinants of birth interval; (2) To assess the impacts of breastfeeding duration, use of contraception and other socio-demographic factors on birth interval by taking it as the proxy for the fertility levels; (3) To evaluate whether breastfeeding duration is used deliberately to space or limit the number of children.