Most of the time, hormonal birth control doesn't fail. When people use hormonal birth control consistently and correctly, pregnancy occurs in only 0.05 percent to 0.3 percent of people (depending on the method) over a year of use (1).

How often is birth control ineffective?

In real life, birth control pills have a 9 percent failure rate. That means nine of every 100 women using birth control pills as their only means of contraception become pregnant in any given year. "It's hard to actually [take the pill at the same time every day] when you're living a busy life," Cullins says.

What is the most ineffective birth control?

By itself, spermicide prevents just 72% of pregnancies, the least effective of any major contraceptive measure. Because of its poor success rate, spermicide is often used in conjunction with other contraceptives such as patches and condoms.