Selective effects in potential fertility: a simulation study.

"The effect of various factors on selection for family planning status and for natural fecundability is studied in a Monte Carlo simulation that incorporates heterogeneity of natural fecundability and of risks of foetal loss. Selection depends crucially on the duration of marriage at which contraceptive status is recorded, and on desired family size....The contraceptive status of sterile women is also revealed in the simulation, including users who do not know that they have become sterile. Formulae are developed to allow the estimation of births averted and potential fertility among the users, and results checked by further simulation." The results indicate "that selection for foetal loss is much less important than selection for natural fecundability in its effect on numbers of averted births and potential fertility." (summary in FRE)