The age is one of the the most important demographic variables. Many of the functions related to demographic phenomena are considered functions on age. In particular, age at first marriage has a direct impact on fertility levels, since increasing the age at first marriage leads to decrease the duration of marriage, and the duration of marriage has a strong direct relationship with actual reproduction. and around puberty starts the woman’s ability to reproduce at low level, and it rises with increasing age until it reaches a maximum at a certain age to start decreasing until it stops at menopause. There is also a positive relationship between duration of marriage and actual reproduction, the actual reproduction stops with the end of marriage either by divorce or widowhood, although the ability of one or both parties to reproduce is existing. Age and duration of marriage are direct variables that affect fertility if one of them has changed and the other remains constant.