Pre-transitional populations: Natural Fertility

Fertility is directly determined by so-called intermediate fertility variables or proximate determinants which are, in turn, affected by indirect determinants such as socio-economic, cultural and environmental variables. Many different proximate determinants influence fertility and the relationship between them and the level of fertility can be analysed using a comprehensive model. The result of this analysis shows that variations in four factors – marriage, contraception, lactation and induced abortion – are the primary proximate causes of fertility differences among populations. While fertility variations can always be traced to variations in one or more of the intermediate variables, the scope for variation differs among the variables as does their degree of influence in different societies and over time within societies.