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 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 prevalence and effectiveness of contraceptive practice to implement these preferences, and the probability of undergoing an abortion when contraceptives fail or are not used.
In societies where large families are desired, the potential unintended pregnancy rate tends to be low. As societies move through the fertility transition, the desired number of children declines along with the number of years needed to reach desired family size. Therefore the number of years during which women are potentially at risk of experiencing an unintended pregnancy increases commensurately. Estimates of the desired number of children range from approximately five in sub-Saharan Africa to two in the Western world.
Spacing preferences also influence the potential unintended pregnancy rate. Women who prefer longer birth intervals are at greater risk of experiencing unintended pregnancies. This consideration is important in the analysis of abortion rates, Bongaarts and Westoff say, because mistimed as well as unwanted pregnancies are potentially subject to termination.
The actual rate of unintended pregnancy depends not only on the potential rate, but also on the extent to which women use contraceptives and on their effectiveness. In theory, if all fecund women who did not wish to become pregnant practiced contraception that is 100 percent effective, there would be no need for abortion. Because not all such women practice contraception, and because methods are less than 100 percent effective, and because even effective methods are sometimes misused, perfect contraceptive use is only an ideal. Contraceptive prevalence varies around the world from less than 10 percent of women of reproductive age in some sub-Saharan countries to around 75 percent in many developed countries.
Use of Abortion Varies Among Regions
Just as contraceptive prevalence varies around the world, so does the use of abortion to terminate pregnancies, the authors note. The proportion of unintended pregnancies that end in abortion is estimated at 58 percent worldwide, but there are large variations among regions. This proportion is higher in the developed world (73 percent) than in the developing world (54 percent), ranging from a high of 91 percent in Eastern Europe to a low of 41 percent in Africa.
"In general, abortion rates are highest in societies where small families are desired, because of the increase in the risk of unintended pregnancy; in societies where low contraceptive prevalence or use of ineffective methods is combined with low-fertility norms; and in societies with a high propensity to rely on induced abortion. Relatively low abortion rates are found in societies with high desired fertility or high levels of use of effective contraception, or with a low propensity to rely on abortion," say the authors.
Family planning programs, which are now implemented in many developing countries, have helped lower the abortion rate by increasing access to contraceptive services through clinics and community-based distribution systems and by providing education and counseling. "The reach and quality of these services are still far from adequate in many developing countries, so that recourse to abortion remains more prevalent than is desirable," the authors conclude.
