Abortion rates reflect the optimization of parental investment strategies.

Parental investment decisions in human beings, including infanticide, have usually been considered in relation to the postnatal survival probabilities of their children. A number of factors which influence parental ability and willingness to invest in offspring have been identified from these studies. Here we argue that at least some of the same factors which influence investment decisions postpartum also affect the decision to terminate a current pregnancy through voluntary abortion. We show that both female age and marital status influence the probability of abortion, with the key variable being the likelihood of future marriage. Thus, abortion procedures extend a woman's ability to manage her reproduction into the prenatal period.