A report by the Guttmacher Institute, which works to advance sexual and reproductive health, found 19 percent of women who used contraception inconsistently accounted for 43 of unintended pregnancies, while the 16 percent who used no contraceptive method at all for a month or more during the year accounted for 52 percent of unwanted pregnancies.
"These simple statistics demonstrate how effective contraceptive use can be," the report said. "They also categorically refute claims by anti-contraception activists that access to contraception somehow leads to more unintended pregnancies and subsequent abortions."
Most U.S. women having abortions were either not using any contraception or were using a method inconsistently, the report said.
In 2000, the most recent year for which data was available, almost 46 percent of women who got an abortion were not using a contraceptive method in the month they got pregnant.
Among the 54 percent of abortion patients who were using some form of contraception, the overwhelming majority acknowledged their use was inconsistent, the report said.
The population of women obtaining abortions did not include the large majority of consistent contraceptive users, since they did not experience an unintended pregnancy and therefore never had a need for abortion services, the report said.
The report also found one-third of sexually active U.S. women who want to avoid an unintended pregnancy did not use a contraceptive method consistently and correctly.
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