Even modest increases in effective contraceptive use can reduce abortion rates, say two leading demographers. By developing a mathematical model that links the abortion rate to its direct determinants, Population Council scientist John Bongaarts and Princeton University professor Charles Westoff show how increased contraceptive use and effectiveness can reduce abortion rates. Their analysis is published in the September issue of the Population Council's journal, Studies in Family Planning.
Bongaarts and Westoff describe the relationship between a range of factors--number of reproductive years per woman, desired total fertility rate, abortion propensity, contraceptive prevalence, and the effectiveness of contraception--and the total abortion rate. The model allows them to estimate how reductions in abortion rates can be achieved by increases in contraceptive prevalence and effectiveness. According to their analysis, a woman who used no contraception would need about 12 abortions to restrict her fertility to two births.
For example, in a population with an abortion probability of 0.5 (meaning half of all unwanted pregnancies would end in abortion), a 10 percentage-point increase in contraceptive prevalence would avert approximately 0.45 abortions per woman, assuming contraception is 95 percent effective.
Worldwide about 133 million births occur annually; of these, experts estimate about 33 million (one-fourth) are unintended. In addition, an estimated 46 million induced abortions are performed, bringing the total number of unintended pregnancies to roughly 79 million per year. Almost as many unintended as intended pregnancies occur each year, and more than half of these unintended pregnancies end in abortion.
Several Factors Influence Rate of Abortion
The outcome of a pregnancy--whether it ends in a birth or induced abortion (miscarriages were excluded from the analysis)--depends on three factors: the desired number and spacing of births, the
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