Pregnancy wastage among Egyptian females: a failure rate model.

Data on duration of pregnancy prior to abortion (loss during the first 6 months) or stillbirth (loss after 7 or more months of pregnancy) from a national demographic survey undertaken in Egypt in 1980 (of 12,749 pregnancies, 1378 ended in abortion and 293 in stillbirth) were analyzed in the context of hazard function (failure rate) models. Such models are generally used in demography to estimate statistical properties of distributions. This report describes the concepts of life time distribution and related functional forms. It then describes the fitting method used (the hazard plotting method which provides a simple graphical means for obtaining estimates of distributions of time to failure data with different failure models). After discussing the method application and findings, the report ends with information on parameters estimation and goodness of fit testing.