Analysis of Birth Spacing Using Frailty Models

Introduction Fertility is considered to be one of the most important components of population change and is affected by birth spacing, which is correlated with the total number of live births of any woman during pregnancy. Birth spacing is defined as the interval between two live births and determines the fertility rate. In addition, it provides the opportunity for assessing attitudes related to the size of the household, fertility differences and child mortality rate. Today, the mean birth spacing of a woman in any country is an indicator for assessing the socioeconomic development and life quality in that region (1). Many studies in developing countries have shown that women with large and small families have a smaller and larger birth spacing, respectively. Therefore, there is a reverse relationship between birth spacing and total or cumulative fertility of a woman. The interval between marriage and the birth of the first child of a woman leads to a rapid transition to subsequent childbirths and, as a Article Type: Original Article