By Barbara Goldberg

NEW YORK (Reuters) – Abortion rates among U.S. women in all age groups plunged to a decade low, with teens experiencing a greater decrease than older women, the Centers for Disease Control and Prevention said on Wednesday.

Statistics for 2015, the most recent year for which data is available, show the abortion rate was 11.8 abortions per 1,000 women aged 15 to 44. That is down 26 percent from 2006, when the study began and the rate was 15.9 abortions per 1,000 women.

Among teens aged 15 to 19, the rate decreased 54 percent from 2006 to 2015, the CDC said.

“This decrease in abortion rate was greater than the decreases for women in any older age group,” the CDC said in a statement.

The CDC did not provide any reason for the decline in the rates, but the drop comes amid efforts by many states to restrict a woman’s access to the procedure.

The total number of reported abortions fell to 638,169 in 2015, from 842,855 in 2006, a 24 percent decrease. In 2015, there were 188 abortions per 1,000 live births, compared with 233 abortions per 1,000 live births in 2006, a drop of 19 percent.

In 2015, all measures reached their lowest level for the entire period of analysis (2006-2015), the CDC said of the annual study, “Abortion Surveillance-United States 2015.”

Conservative state lawmakers are passing increasingly restrictive abortion laws in a challenge to Roe v. Wade, the U.S. Supreme Court’s 1973 landmark decision that established that women have a constitutional right to an abortion.

The Republican-controlled Ohio House of Representatives last week approved a measure that would ban abortions at six weeks, while an Iowa law banning abortions after a fetal heartbeat is detected is tied up in a court battle.

Such laws are designed to be thrust into a Supreme Court that has become more conservative following President Donald Trump’s appointments of Justices Neil Gorsuch and Brett Kavanaugh.

The CDC study also showed nearly all abortions, 91.1 percent, performed in 2015 were in a woman’s first 13 weeks of pregnancy. There was also a shift toward earlier abortions, with the number performed at six weeks or less increasing 11 percent.

(Reporting by Barbara Goldberg in New York; Editing by Steve Orlofsky)