prognostic factors of first birth interval using the parametric survival models

background: in recent years, the study of birth intervals has been a main determinant of the levels of fertility in the populations, as it is associated with rates of fertility and population growth. objective: the purpose of this study was to firstly apply survival analysis for modeling of first birth interval and secondly to explore its determinants. materials and methods: in a cross sectional study, the fertility history of 858 women was collected in rural areas of shiraz (southern iran) in 2008. we used the survival analysis such as cox regression and alternative parametric models to evaluate the prognostic factors of first birth interval. results: among the explanatory variables of interest, age at marriage, level of women's education, and menstrual status had highly significant effects on the duration of birth interval after marriage (p<0.01). conclusion: it is concluded that the suitable parametric models would be a useful tool for fitting to first birth interval, the fact that has been less paid attention to in researches