Abortion has hit the front burner of American political discussion again with the announcement by Supreme Court Justice Anthony Kennedy that he will resign, and President Donald Trump’s promise to nominate a replacement next week.

Kennedy was the swing vote on several key abortion rights rulings, including the 1992 case known as Planned Parenthood v. Casey that found states may not impose an “undue burden” on a woman’s right to abortion.

Now, opponents of abortion rights hope Trump will appoint a justice who would swing the court away from supporting women's access to abortion.

Here are a few facts about abortion in the U.S.:

Most Americans support abortion rights

Surveys show that most Americans support a woman’s right to have an abortion. Last month, the latest survey by the Kaiser Family Foundation found that 67 percent of those polled supported Roe v. Wade, the 1973 Supreme Court ruling that supported abortion rights under the constitutional right to privacy. The issue is highly partisan, the survey found. About half — 53 percent — of people who said they were Republican would like to see Roe v. Wade overturned, while 81 percent of Democrats and 73 percent of independents want it to stand.

A 2013 NBCNews/Wall Street Journal poll found that 54 percent of Americans believed abortion should be legal all or most of the time and 70 percent supported Roe v. Wade.

In 2013, 89 percent of abortions occured in the first 12 weeks. Guttmacher Institute

Legal abortion is safe

Opponents of legal abortion use a variety of arguments to discourage women from having them or to make it more difficult to provide them. Texas has some of the strongest laws, requiring clinics to meet stringent requirements that legislators say would protect the health of women seeking abortions.

Kennedy was the swing vote in a 2016 Supreme Court decision striking down a Texas law that would have required abortion clinics to meet the same standard as ambulatory surgical centers. Medical experts overwhelmingly said such regulations were unnecessary. Earlier this year, the National Academy of Medicine reported that abortion care is safe in the U.S. It found that abortions can be safely provided in clinics and doctor’s offices.

Fewer than 1 percent of first-trimester abortions lead to complications, one review found.

“The risk of death associated with childbirth is approximately 14 times higher than that with abortion,” the American College of Obstetricians and Gynecologists (ACOG) says.

Studies have also debunked the argument that abortions raise the risk of depression or breast cancer.

Yet states still seek to restrict access to abortions. According to the Guttmacher Institute, which studies women’s reproductive health, 29 states impose “major” restrictions on abortion access.

Banning abortion does not reduce it

Countries that restrict abortion the most have the highest rates of abortion, the Guttmacher Institute found. "The abortion rate is 37 per 1,000 women in countries that prohibit abortion altogether or allow it only to save a woman’s life, and 34 per 1,000 in countries that allow abortion without restriction as to reason — a difference that is not significant," Guttmacher said in a report issued in March.

“Historical and contemporary data show that where abortion is illegal or highly restricted, women resort to unsafe means to end an unwanted pregnancy, including self-inflicted abdominal and bodily trauma, ingestion of dangerous chemicals, self-medication with a variety of drugs, and reliance on unqualified abortion providers,” ACOG says. “Today, approximately 21 million women around the world obtain unsafe, illegal abortions each year.”

In the U.S. before Roe v. Wade, ACOG says an estimated 1.2 million U.S. women got illegal abortions every year, and says unsafe abortions killed as many as 5,000 of them. “After the Supreme Court ruling, mortality due to septic illegal abortion decreased precipitously,” ACOG said.

Providing free birth control does reduce abortion rates

Colorado provides a real-life experiment on whether providing safe, effective, long-acting birth control can reduce unwanted pregnancies and abortions. The state’s Department of Public Health and Environment got private funding in 2008 for a program to provide long-acting reversible contraceptives (LARCs), such as IUDs and hormone implants, to low-income women for little or no cost.

Trends in abortion between 1997 and 2014 Guttmacher Institute

“The Colorado Family Planning Initiative helped cut the abortion rate nearly in half for women aged 15-19 and by 18 percent for women aged 20-24,” the department said in a 2017 report. “Between 2009 and 2014, birth and abortion rates both declined by nearly 50 percent among teens aged 15-19 and by 20 percent among young women aged 20-24.”

Abortion is very common in the U.S.

“In the United States, where one half of all pregnancies are unintended, almost one third of women will seek an abortion by age 45,” ACOG says.

A 2016 study in the New England Journal of Medicine found that 45 percent of all pregnancies among U.S. women in 2011 were unintended, and 42 percent of them these unintended pregnancies ended in abortion.

According to the Guttmacher Institute, 19 percent of pregnancies ended in abortion in 2014, a total of 926,200 abortions. That was down 12 percent from 2011. The 2014 abortion rate of 14.6 abortions per 1,000 women was the lowest rate ever measured. In 1973, the rate was 16.3 abortions per 1,000 women, aged 15 to 44.