| Abstract: | Abstract The calculation of the number of births prevented for each item of contraceptive service provided entails the integration of a variety of factors relating to the potential fertility of users and the duration and effectiveness of use. This article differs from previous essays of this kind in that estimates of future potential fertility are based not on fertility rates but on age-specific means of inter-live birth intervals, modified by periods of use overlapping post-partum sterility, and by the probabilities attached to the development of permanent sterility and to the successful adoption of extra-programme birth control. In the first three years after acceptance of intra-uterine contraception by some 9,000 postpartum women of several ethnic origins in Singapore, it is calculated that about 4,800 births were prevented. |
