A Multistate Model of Fecundability and Sterility.

The article presents a paper on model for estimating fecundability and sterility. The paper presents a new method for estimating fecundability and sterility simultaneously, based on a multistate hazards model. The most important features of the model are: one, the presence of distinct sterile and nonsterile states; two, a clear distinction between preexisting sterility and sterility that begins after initiation of follow-up; and three, a log-normally distributed hazard of conception among nonsterile couples. These features allow the investigators to address several important biological questions about fecundability and sterility. Application of the model to data on first birth intervals from Taiwan, Sri Lanka, and the Amish shows that heterogeneity in fecundability is statistically significant at most ages, but that preexisting sterility and new sterility are unimportant before age 40. These results suggest that sterility may not be an important determinant of natural fertility until later reproductive ages.