Media playback is unsupported on your device Media caption Inside Mississippi's last abortion clinic

The rate at which US women had abortions fell between 2008-11 to the lowest level since abortion was legalised in 1973, a study suggests.

The Guttmacher Institute, which supports abortion rights, also reported the total number of abortions fell 13%.

Researchers said the drop coincided with a declining pregnancy rate and increased use of contraceptives.

They said the decline predated passage of a recent wave of state laws restricting access to abortion.

"Contraceptive use improved during this period, as more women and couples were using highly effective long-acting reversible contraceptive methods, such as the IUD," the study's lead author Rachel Jones said in a statement accompanying the report.

"Moreover, the recent recession led many women and couples to want to avoid or delay pregnancy and childbearing."

The report, which took into account numbers of abortions reported by clinics and state health departments, found the US abortion rate fell to 16.9 abortions per 1,000 women in 2011, down from the 1981 peak of 29.3 per 1,000.

It was the lowest rate since 1973, when the rate was 16.3 abortions per 1,000 women.

In 1973, the US Supreme Court legalised abortion across the country, in a landmark decision known as Roe v Wade.

In the 2008-11 period of the study, the number of clinics offering abortion only decreased 1%.

But Carol Tobias, president of the National Right to Life Committee, said the overall drop in abortion numbers was evidence that the anti-abortion movement's efforts were working.

"It shows that women are rejecting the idea of abortion as the answer to an unexpected pregnancy," she said.

The highest abortion rates were in New York, Maryland, Washington DC, Delaware and New Jersey.

The lowest were in Wyoming, Mississippi, South Dakota, Kentucky and Missouri.

However, Guttmacher said many women in Wyoming and Mississippi, where there are very few providers, go out of state to get abortions.

Republicans made extensive gains at the state level in the 2010 elections, using their new-found power to pass anti-abortion measures in states across the country.

According to a Guttmacher Institute tally, a total of 205 abortion restrictions were passed between 2011-13, more than in the entire previous decade.