Major abortion ruling expected from Supreme Court on Monday

The U.S. Supreme Court is due on Monday to issue its first major abortion ruling since 2007 against a backdrop of unremitting divisions among Americans on the issue and a decades-long decline in the rate at which women terminate pregnancies.

The court's decision on whether a Republican-backed 2013 Texas law placed an undue burden on women exercising their constitutional right to abortion is one of three remaining cases for the court to decide on Monday, the last day of its term. The other major one involves whether the justices will overturn the corruption conviction of former Virginia Governor Robert McDonnell.

The last time the justices decided a major abortion case was nine years ago when they ruled 5-4 to uphold a federal law banning a late-term abortion procedure.

Americans remain closely divided over whether abortion should be legal. In a Reuters/Ipso online poll involving 6,769 U.S. adults conducted from June 3 to June 22, 47 percent of respondents said abortion generally should be legal and 42 percent said it generally should be illegal.

Views on abortion in the United States have changed very little over the decades, according to historical polling data.

There has been a long decline in the U.S. abortion rate. The most recent data, from 2011, showed that there were an estimated 1.1 million abortions that year at a rate of 16.9 per 1,000 women ages 15 to 44, according to the Guttmacher Institute, which tracks abortion policy and supports abortion rights. The rate had peaked at 29 abortions per 1,000 women in 1981, the group said.

"We know that the recent abortion declines were primarily due to declines in unintended pregnancies. Improved contraceptive use is likely the key driver of the declines in both unintended pregnancy and abortion," said Elizabeth Nash, a policy analyst at the institute.

The Supreme Court legalized abortion nationwide in its landmark 1973 Roe v. Wade ruling.

The law in Texas, one of a number of conservative states that have pursued restrictions on abortion, requires abortion doctors to have "admitting privileges," a type of formal affiliation, at a hospital within 30 miles (48 km) of the clinic. It also requires clinics to have costly hospital-grade facilities.

The court is evenly divided between liberals and conservatives following the February death of conservative Justice Antonin Scalia. The court could split 4-4, which would leave in place a lower court's decision upholding the law.

In the Reuters/Ipsos poll, Americans were nearly evenly split on whether they backed laws like the one in Texas, with 43 percent generally opposed and 41 percent generally supportive. The poll had a credibility interval, a measure of accuracy, of about 2 percentage points.

(Reporting by Lawrence Hurley; Editing by Will Dunham)