A multistate model of fecundability and sterility

Use of a multistate hazards model to analyze data on time between marriage and first conception helps simultaneously predict sterility and fecundability. The model accounts for separate nonsterile and sterile conditions, distinguishes between already present sterility and sterility that commences after the beginning of follow-up and has a log-normal distribution of the chance of conception in fertile couples. Analysis of data from the differing populations of Sri Lanka, Taiwan and an Old Order Amish community in Pennsylvania reveals that sterility might be a significant determinant of natural fertility only after the age of 40.