Context: Abortion levels may differ between subgroups of women because of variations in the level of unintended pregnancy and in the likelihood that women will choose abortion if they become pregnant unintentionally. Understanding differentials in levels of abortion according to women's characteristics can shed light on the circumstances surrounding the reasons leading to abortion.

Methods: Data from government statistics, nationally representative sample surveys and subnational sources are used to estimate percentage distributions of abortions and abortion rates and ratios by selected characteristics of women, particularly age at abortion, marital status and parity. Comparisons are made within and across countries.

Results: Women aged 40 and older generally obtain the lowest proportion of abortions (10% or fewer in most countries). Although adolescents account for a high proportion of abortions in some countries (for example, 33% in Cuba and 22% in Scotland), they do not obtain a disproportionate share of procedures. In general, abortion rates by women's age show an inverted U-shaped pattern. Abortion ratios by age, however, show two patterns: a U shape and a monotonic increase with age. In more than half of the countries studied, married women obtain a larger proportion of abortions than unmarried women. However, once pregnant, unmarried women are more likely than married women to choose abortion. More than half of abortions are obtained by women with at least one child. Some variations exist in these patterns by region.

Conclusions: Women's characteristics influence their likelihood of terminating unintended pregnancies. However, within all demographic and socioeconomic subgroups, some women will obtain an abortion when faced with an unintended pregnancy