This book chapter presents a model of fertility that includes concepts for the price of womens time and relative female income. The model is based on one proposed by Pollak and Watkins (1993) which allows for preference changes. Fertility is represented by the timing of first births. The proposed model of fertility is based on formulations by Fair and Macunovich (1996). The proposed model includes the price of time and the Easterlin relative income models. Two different formulations are tested that express varying female wages over time and varying female wages as a function of male income. Independent variables are lagged a year in order to account for the time lapse between conception and birth. Data are obtained from the March Current Population Survey for years 1964-95 and Vital Statistics Reports and Advance Reports. Findings indicate that 99% of the variance in observed fertility for women aged 20-24 years was explained in the first model. Male relative income (RY) was positive and highly significant and female wage factors were negative and highly significant. There was little serial correlation. Findings indicate that the net effect of the female wages on fertility changed over time. As female wages rose women focused less on male income for childbearing decisions. The findings remained stable in the 1969-93 the 1969-80 the 1975-93 and the 1981-93 samples. The numerator and the denominator of relative income were tested separately as was the net effect of the female wage on fertility in the two aforementioned ways. The models projecting fertility until 2004 based on three different assumptions indicate that the effect of the female wage on fertility depends upon the level of RY. Findings provide strong support for the strong influence of RY on three decades of significant socioeconomic changes and the importance of the opportunity cost of time for child rearing in fertility decision making. High female unemployment did not provide opportunity for pregnancy.