The U.S. abortion rate has fallen to its lowest level since 1976, with about 20 percent of pregnancies being terminated by abortion, the nonprofit Alan Guttmacher Institute reported on Thursday.

Its survey of all known abortion providers found the abortion rate fell 9 percent between 2000 and 2005, probably due to a combination of better access to contraception and less access to abortion providers, the group said.

“Slightly more than one in five pregnancies end in abortion, indicating that unwanted pregnancy is still too common in the United States,” the report reads.

The report is the first snapshot since 2000 of what remains one of the most contentious political and ethical issues in the United States - whether women should be able to get abortions. While it remains legal, some states have passed laws designed to make it more difficult to get an abortion.

“More needs to be done to help women and their partners prevent unintended pregnancy,” a team of experts led by the institute’s Rachel Jones wrote in the report.

“For example, more women and couples need access to resources and services that will help them to better plan when they want to have children and how to use contraceptive methods effectively until that time,” the report said.

“In addition, it is important to remove barriers to abortion services - particularly for lower income women, who have above-average rates of unintended pregnancy.”

They used surveys from all abortion providers they could find along with data from the U.S. Census Bureau to calculate rates.

“An estimated 1.2 million abortions were performed in the United States in 2005, 8 percent fewer than in 2000,” they wrote. “The abortion rate in 2005 was 19.4 per 1,000 women aged 15 to 44; this rate represents a 9 percent decline from 2000.”

They found that 1,787 doctors, clinics and hospitals provide abortion, just 2 percent fewer than in 2000. But 87 percent of U.S. counties had no abortion provider, meaning women often must travel to get one.

Women can get abortions surgically or by using a combination of drugs to induce a miscarriage. The report found that using the drugs accounted for 13 percent of all abortions.

The institute, set up to study and report on reproductive health in the United States, said no one had reported on the abortion rate since 2000.

“Abortion is one of the most common medical procedures undergone by women aged 15-44 in the United States, partly because of the high level of unintended pregnancy,” Jones and colleagues wrote.

“About half of the 6.4 million pregnancies that occurred in 2000 (including those ending in miscarriages) were unintended, and about half of these resulted in abortion,” they wrote.

The researchers said the number of abortion providers declined by about 38 percent between 1982 and 2000, but that appeared to be leveling off.

2008 Reuters Limited - WASHINGTON