Fact check: how well does your birth control work?

Hello, how are you today? If you’ve got a uterus, maybe the answer is “not so great” – especially if you’ve heard reports about Donald Trump’s latest appointee. The woman tipped for a key family planning role, Teresa Manning, has previously worked with an anti-abortion group as well as an anti-LGBT rights lobbying group.

If Manning is appointed as deputy assistant secretary for population affairs at the Department of Health and Human Services, she would have oversight of the federal program that provides contraceptive services to low-income and uninsured women and men.

Manning, who is a law professor, has said “family planning is something that occurs between a husband and a wife and God, and it doesn’t really involve the federal government”. I won’t be fact-checking that statement (because it’s tricky to prove who does and who does not have a direct line to chat to God), but rather Manning’s claim that contraception doesn’t work well.

Here’s Manning’s statement in full which she gave in full during a radio interview:

Its efficacy is very low, especially when you consider over years – which, a lot of contraception health advocates want to start women in their adolescent years, when they’re extremely fertile, incidentally, and continue for 10, 20, 30 years. The prospect that contraception would always prevent the conception of a child is preposterous.

Let’s fact-check this.

Step 1: Do an internet search for “contraception efficacy rates”. You’ll very quickly land at this summary published by the Centers for Disease Control and Prevention (CDC). It shows that the effectiveness of contraception varies depending on which method is being used.

They range from spermicide (which is the least effective, with about 28 out of every 100 women who use it becoming pregnant on average within the first year of typical use) to the hormonal implant (which is the most effective, with one out of every 200 women becoming pregnant in the first year of typical use).

Step 2: Check the reliability of your source. While Wikipedia is certainly not the most accurate site on the internet, the thousands of editors who regularly work there can be more inclined to dig up criticism than the standard “about” page on a website.

The Wikipedia page on the CDC offers few leads about a corrupt, biased organization – rather, the CDC is simply described as a federal agency whose “main goal is to protect public health and safety through the control and prevention of disease, injury, and disability in the US and internationally”. The organization doesn’t seem to have an interest in overstating the effectiveness of contraception.

Step 3: Understand the terms used. The CDC talks about “typical use” and that seems kind of important, so I repeat the same internet search but this time with those two words added in there.

I land at this New York Times page, which has been built using data compiled by James Trussell from the Office of Population Research at Princeton University and also the Brookings Institution. Here’s how they define typical use:

“This is the norm, reflecting the effectiveness of each method for the average couple who do not always use it correctly or consistently.”

That makes sense. It is part of the reason why methods that require planning (eg “Babe, do you have the spermicide?”) or some other action before or during sex (“Don’t worry, I’ll pull out in time”) are much less effective than those that don’t (hormonal implants, intra-uterine devices and sterilization require much less upkeep).

Perfect use, by the way, is defined as:

“A measure of the technical effectiveness of each method, but only when used exactly as specified and consistently followed. Few couples, if any, achieve flawless contraceptive use, especially over long time periods.”

If 100 women were to use the pull-out or withdrawal method “perfectly”, 34 of them would wind up pregnant within 10 years (yep, that’s the 10-year use period Manning mentioned). But even with perfect use, there’s still a significant gap between different contraceptive methods. If those same women were to use a hormonal implant, chances are only one would be pregnant at the end of 10 years.

By appointing Manning, an opponent of Planned Parenthood, Trump takes another step towards his goal: defunding it. As a result, the availability of contraception such as the hormonal implant will be curtailed.

Step 4: Find a sexually active woman and listen to what she has to say. Ask her whether she wants to have the freedom to choose.

Would you like to see something fact-checked? Send me your questions! mona.chalabi@theguardian.com / @MonaChalabi

Fact check: how well does your birth control work?