How effective are internal condoms at preventing pregnancy?

That all depends on how they’re used. With perfect use, that means using internal condoms correctly every time you have sex, they are around 95% effective, but the way they’re typically used you can expect them to be closer to 79% effective.

In other words:

For people who use the internal condom exactly as directed for a whole year, about 5 in 100 will get pregnant when they don’t want to during the first year they use this method.

For people who do not use the internal condom exactly as directed, about 21 in 100 will get pregnant when they don’t want to during the first year they use this method.