The number of abortions in the United States has increased, reversing what had been a three-decade decline, according to a new report.

The uptick began in 2017 and, as of 2020, one in five pregnancies, or 20.6 percent, ended in abortion, according to the report by the Guttmacher Institute, a research organization that supports abortion rights. In 2017, 18.4 percent of pregnancies ended in abortion.

Overall, the new report found, the abortion rate rose in 2020 to 14.4 per 1,000 women ages 15 to 44 from 13.5 abortions per 1,000 women of that age group in 2017, a 7 percent increase.

During this period, the report said, births nationwide declined by 6 percent, meaning that “fewer people were getting pregnant and, among those who did, a larger proportion chose to have an abortion.”

The report, which found that the number and rate of abortions increased in 33 states and the District of Columbia, said “there were no clear patterns” to explain each state’s trajectory. It suggested several reasons for the national increase, including trends that directly affected low-income people, the population most likely to seek abortions in recent years: Some states expanded Medicaid coverage for abortion, and funds that provide financial assistance to patients seeking abortions expanded.