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Risky business: Is birth control safe?

The biggest risk of using birth control is accidental pregnancy—so how likely is that?

by Joe Speidel, MD, MPH

It’s a common question. For almost all healthy women, the answer is a definite “Yes!” In fact, the most likely health risk of having sex and using a birth control method is the chance that a woman will get pregnant accidentally.

What are the chances that my birth control won’t work?

There’s a lot of information out there about how effective different types of birth control are, but “typical use” numbers are the ones to pay attention to. These numbers are calculated based on women using the method in the real world. Being late to take a pill or refill a prescription happens all the time, and it’s the cause of a big slice (43%) of accidental pregnancies in the U.S. Only a tiny slice (5%) is due to the birth control method itself failing—like when a condom breaks.

If you organize all birth control methods by the chance of accidental pregnancy when real women are using them, here’s what you get:

Planned Parenthood method effectiveness chart

The most effective methods are in the top row. Each row under the top row gets less effective. So basically the risk of pregnancy when using birth control falls into one of these four groups.

Group 1: Couples using methods in the top row—tied tubes, vasectomy, the IUD or the implant—are very unlikely to have an accidental pregnancy. If 100 couples used these methods for one year, less than one woman in the group would become accidentally pregnant. IUDs and implants are totally reversible, but undoing sterilization is expensive and may not work.

Group 2: Most women in the U.S. use methods in the second row—the pill, the ring, the patch, and the shot—all these methods use hormones to prevent pregnancy. The latest research shows that out of 100 couples using these methods in a year, between 6 and 9 of them would become accidentally pregnant. (Another way of saying that is: for every 11 couples using these methods, one woman would become accidentally pregnant.) Moms can use exclusive breastfeeding for up to six months after baby’s birth for about the same level of protection.

Group 3: Methods in the third row include condoms, female condoms, the diaphragm, the cervical cap, the sponge, and fertility awareness. If 100 couples used these methods for a year, between 18 and 24 of them would become accidentally pregnant. (Or for every 5 couples using these methods, one woman would become pregnant.)

Group 4: The least effective methods in the fourth row are withdrawal and spermicide (which comes as a cream, gel, or foam). If 100 couples used these methods for a year, about 30 of them would become accidentally pregnant (or one out of every 3 couples.) The latest data shows that withdrawal may actually be slightly more effective than researchers previously thought.

Wait a minute—did you say that pregnancy is a health risk?

We talk about how pregnant women “glow,” have luxuriant hair, or otherwise seem especially healthy, but we talk a lot less about the health risks that come with pregnancy. Pregnancy is great when you’re ready for it, but the risks are one of the reasons that doctors recommend that women plan their pregnancies. So…what are they?

Scariest first: about one of every 8,300 pregnant women in the U.S. dies giving birth. That’s about the same risk as dying in a car accident in the U.S. Pregnancy also increases a woman’s risk for diabetes, high blood pressure, and blood clots. A recent study showed that only about half of women were aware of these increased risks. In that study, the majority of women (76%) thought the pill was more dangerous than pregnancy. Actually the opposite is true—for non-smoking women 15-34 years old who use the pill for a year, the risk of death is tiny, at about one in 1,667,000. That’s about the same risk as dying from being struck by lightning.

The news is full of sensational headlines about the risks of birth control, so it’s understandable that women might overestimate the danger. The truth is that birth control is generally safe, and there are enough methods out there that couples are likely to find one that is right for them. Some women do have health conditions that increase the risk of using some kinds of birth control, so it’s always good to get personalized advice from a healthcare professional. Fortunately, the methods in Group 1 that do such a good job of preventing accidental pregnancy are safe for almost all women.


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