Pregnancy outcome and the time required for next conception

Abstract

Variations in the time required for next conception by outcome ofthe preceding pregnancy, and the age of woman, are studied for Taiwanese women. Pregnancy interval, defined as the period between the end of one pregnancy and the beginning of the next, is taken as a measure of the time required for the next conception. The averages and variances of pregnancy intervals are estimated from reports of pregnancies occurring in a probability sample of 2,443 married women, aged 20–39, living in Taichung (Taiwan) in 1962. The effects of ‘truncation bias’ and ‘memory bias’ on the two moments of pregnancy intervals are estimated indirectly by cross-classifying women according to their ages at interview and their ages at the beginning (or end) of each pregnancy interval. The moments of post-partum amenorrhoea are, then, estimated indirectly from the moments of pregnancy intervals. The effects of truncation bias and memory bias are compensatory in this sample. In the absence of contraception, women, on an average, took longer to conceive following a live birth than following a foetal death. The time taken for next conception increases as women become older irrespective of the outcome of the preceding pregnancy.