Distribution of time of first birth in presence of social customs regulating physical separation and coital frequency.

The interval between marriage and the first birth in India, particularly in rural areas, is much longer than what is observed in western countries. In eastern Uttar Pradesh, the mean interval is observed to be even longer, possibly due to traditional customs such as the female partner's visits to her parents in the early years of marriage and the smaller chance of coition because of the observance of rigid intercourse taboos. Thus the models to explain the length of the interval of marriage to first birth proposed by Western demographers, which assume that the period of cohabitation between marriage and first birth is uninterrupted, often do not describe the data satisfactorily when applied to rural India. In this paper a model to describe data on first birth interval is proposed that takes account of the distributions of timing and periods of physical separation and variation in fecundity with effective marriage duration.