According to studies, around one in every 50 women who use condoms correctly for a complete year of sex will become pregnant. Even when you account for people who use condoms in the wrong way, they are still very effective, with 15 pregnancies happening out of every 100 women who have intercourse in a year. When used appropriately, a condom is an extremely efficient form of birth control—as well as protection against sexually transmitted infections (STIs).