Welcome to Rumors I Heard About My Body, a recurring feature in which we answer questions about women's health in partnership with Planned Parenthood.
Q: If I go on the pill, what will happen? How do I decide which kind of pill is right for me?
A: Fifty-plus years after the birth-control pill hit the US market, there's still a lot of misinformation out there about oral contraception, its effectiveness, and its drawbacks. There are also a lot of unfortunately hysterical headlines about what the pill does to women's minds and bodies. More on those in a minute.
Now, the basics. If taken as directed, the pill is 99 percent effective. That's known as "perfect use." With "typical use" (i.e., not quite so perfect), it's about 91 percent effective. Those are pretty good odds. "There are two different types of pills available," says Dr. Raegan McDonald-Mosley, chief medical officer of the Planned Parenthood Federation of America. "And within those two categories there are lots of different choices." The first type is a combination pill that contains the hormones progestin and estrogen. The other is a progestin-only pill, also known as the minipill. Both types are safe and effective for the majority of women, and in many countries (and now Oregon and California), women can get the pill over the counter without a prescription.
Most people who are on the pill take the combination pill, which works in a few ways. The progestin thickens cervical mucus, so sperm can't move into the fallopian tubes. The estrogen suppresses ovulation, so the egg is not released. Suppressing ovulation is what really makes this pill work (no egg, no fetus), according to Dr. McDonald-Mosley. The other mechanism is secondary, but both function together to make a very effective form of birth control.
This pill comes in several different formulations. Some are designed to mimic the menstrual cycle, which means there is a week of placebo pills (i.e., pills with no hormones in them) or a week of no pills at all, so that you bleed as you would if you weren't taking the pill. There are other formulas that allow you to limit your period to just three or four times a year. "It's not medically necessary to have a once-a-month menstrual cycle," Dr. McDonald-Mosley explains.
Wait, there's more! Some combination pills are "monophasic," which means each active pill has the same amount of hormones, while some pills are "multiphasic," which means the amount of hormones in each individual pill varies throughout the month. Discuss with your medical professional which pill might be right for you, because differently formulated pills interact with each of our unique bodies idiosyncratically.
The progestin-only pill does mainly one thing: it thickens the cervical mucus, though it may also inhibit ovulation. Maintaining the level of progestin necessary to thicken the mucus is why it's much more important to take the minipill at the same time every day — and why they are potentially less effective. If you're not vigilant about this kind of thing (or if you travel a lot), the minipill might not be right for you. Progestin-only pills tend to be recommended for those who are breast-feeding, have a history of blood clots, or are taking other medications that may interact poorly with the combination pill.
Which brings me to side effects. Like all medications, both prescription and over-the-counter birth-control pills have some downsides. They may increase your blood pressure, your cholesterol, and your risk of blood clots. The blood-clot thing is the one that inspires those fearmongering headlines about birth control potentially murdering you. While it's true birth control does increase the risk of blood clots, the overall risk is still incredibly small, even for women on the pill. Though it's worth noting that the risk is higher for women over 35, women who smoke, and women who have conditions like hypertension.