The paper studies the relationship between cognitive ability, education outcomes, wages, and fertility timing, focusing on how cognitive ability influences fertility decisions. First, the paper presents empirical evidence on the relationship between cognitive ability, early pregnancies, and pregnancy intention using NLSY79 data. Second, I build and estimate a life cycle model to quantify the importance of cognitive ability, wages, marriage, and education outcomes on women’s fertility. To explain the data, the model needs heterogeneous contraception costs by ability, as the relation between cognitive ability with education opportunities and labor opportunity costs can not explain the relation of cognitive ability with fertility timing. Next, I use the model to analyze how decreasing contraception costs affect early pregnancies and women’s educational outcomes. Finally, I study the mechanism behind the decline in teen pregnancies during the ’90s.