"What do these results reveal about the potential effects on birth rates if Roe v Wade were ever to be overturned? The answer depends on the uniformity of the ban on abortions across states. If Roe were supplanted by a constitutional amendment outlawing abortion nationwide, we might expect an 11% rise in fertility rates based on the experience of the early 1970s. Applying this estimate to the current level of births (roughly 4 million per year), we estimate that a complete recriminalizaiton of abortion would result in perhaps as many as 44 000 additional births per year. On the other hand, the effect might be considerably smaller if a future Supreme Court decision returned to states the authority to determine the legality of abortion. The increase in births would then depend on the number of states in which abortion remained legal and their geographic distribution (currently, 13 state have laws on the books to recriminalize abortion if Roe v Wade is overturned). If the 5 repeal states were to maintain the legality of abortion, then our findings indicate that birth rates might still increase by perhaps 4.5% in the remaining states that recriminalize abortion. This would result in an increase in births on the order of 135 000 per year (4.5% of the roughly 3 million births in those states that recriminalize.) If more states were to keep abortion legal, the effect on births probably would be smaller since interstate travel to obtain abortions would increase. While our results provide a useful frame of reference, they have important limitations. Changes since 1973 in contraceptive technology, employment opportunities for women, social attitudes, and other factors have altered the environment in which fertility decisions are made. Moreover, a complete evaluation of the impact of overturning Roe v Wade would require consideration of other social, health, and demographic effects. Nevertheless, our results suggest that if Roe v Wade were overturned today, one of the effects would be a substantial rise in American fertility."