Americans need better access to contraception. In countries where birth control is cheap or free and more easily available to more people, there are much lower rates of unintended pregnancy, said Dr. Emily Godfrey, a professor of obstetrics and gynecology at the University of Washington. The unintended pregnancy rate in the United States is about 21 percent higher than in the average Western country,3 where national insurance or other universal health care programs are common. Likewise, a large drop in unintended pregnancy rates in the U.S. between 2008 and 2011 was correlated to an increase in the use of long-term, reversible methods of birth control, such as IUDs or implants, which have low failure rates. And that large drop in unintended pregnancy rates has led to fewer abortions.

But that’s not the same as saying that using birth control eliminates the need for abortion, Godfrey said. Yes, Americans can choose from 16 forms of birth control, two types of emergency contraception or “morning-after pills,” and three methods of sterilization. But there are many reasons why she says access to abortion remains necessary.

The simplest and most inescapable reason is that birth control can — and does — fail. That’s true even of the most reliable methods of preventing pregnancy, such as IUDs, implants and sterilization.

The reality is, birth control might reduce the need for abortions — but it can’t make abortions go away. That’s because the need for abortion goes beyond the capabilities of birth control, Godfrey said. People can be trying to get pregnant and still end up in situations where they want an abortion. There will always be people who couldn’t get reliable birth control. There will always be people who can’t or don’t want to use specific kinds of birth control. And there will always be people whose birth control simply didn’t work.

Read the full article about birth control by Maggie Koerth and Amelia Thomson-DeVeaux at FiveThirtyEight.