RENEE MONTAGNE, HOST:
It's MORNING EDITION, from NPR News. Good morning. I'm Renee Montagne.
STEVE INSKEEP, HOST:
And I'm Steve Inskeep. Today in "Your Health," we'll talk about birth control.
MONTAGNE: There's been some controversy over insurance coverage, and access to what's known as emergency contraception. It's a pill women can take if their birth control fails, or if they forget to use it. NPR's Patti Neighmond has more on how it works, and who does use it.
PATTI NEIGHMOND, BYLINE: The most popular brand of emergency contraception is Plan B One-Step, sometimes called the morning-after pill. Katie Wilcox is a typical example of who uses it. She's in her 20s, a recent college graduate. She's working now and has a boyfriend. She used Plan B twice. The first time, she was still in college.
KATIE WILCOX: And we kind of got caught up in the moment, I guess you could say, and then woke up in the morning and decided that we needed to go get Plan B because neither of us were ready for any sort of pregnancy.
NEIGHMOND: So Wilcox and her boyfriend headed to their local pharmacy. She presented ID, and was able to buy Plan B without a prescription. The age limit for doing this is 17. After that experience, Wilcox and her boyfriend decided to use condoms. Then, one broke. Again, they turned to Plan B.
WILCOX: I can't even describe how important it was. I think it's an important option for girls at that age to have because things happen. And I think that having Plan B as sort of a back-up plan is really important.
NEIGHMOND: It worked both times. Wilcox didn't get pregnant. Emergency contraception prevents pregnancy 89 percent of the time, if women take it within three days of unprotected sex. It's safe, causing only minor side effects like nausea and headache.
DR. KATHERINE WHITE: All right. So why don't you present the next patient?
UNIDENTIFIED WOMAN: OK. So this is...
NEIGHMOND: At Baystate Medical Center in Springfield, Massachusetts, obstetrician Katherine White talks with a medical student about a new patient. White says most of her patients take Plan B the morning after unprotected sex, but it can work a lot longer.
WHITE: Emergency contraception, or Plan B, can be very effective up to 120 hours, or five days after the act of unprotected intercourse.
NEIGHMOND: Plan B is a high dose of progesterone, the same hormone that's found in birth control pills. It works in several different ways. First, it stops the ovaries from releasing an egg - no egg, no pregnancy. But if an egg has already been released, it can still prevent pregnancy.
WHITE: It can help slow the passage of an egg down into the uterus.
NEIGHMOND: It literally slows down the movement of the egg and at the same time, it slows down the movement of the sperm - making it unlikely the two will meet. But if sperm actually succeed in fertilizing an egg, this is where things get a bit controversial.
Plan B could possibly thin the lining of the uterus - the womb - so the fertilized egg won't attach to it and grow. Scientists have no proof this actually happens but in theory, it could. That's why some people are opposed to Plan B. White says the way Plan B works is still very different than what happens with the abortion pill, mifepristone.
WHITE: So if a pregnancy has already started, Plan B won't do anything to stop it.
NEIGHMOND: White says most patients don't use Plan B instead of regular birth control. Megan Kavanaugh, a senior researcher at the Guttmacher Institute, found the same thing when she looked at national trends.
MEGAN KAVANAUGH: Most emergency contraception users have actually only used it once.
NEIGHMOND: As a back-up plan, the way Katie Wilcox described it. Emergency contraception isn't cheap. It costs, on average, $50. But it can cost as much as $90. Despite the expense, this type of contraception is slowly becoming more popular among women. Today, about 10 percent of sexually active women say they've used emergency contraception.
Patti Neighmond, NPR News.