If the condom broke or leaked while having intercourse, there is a possibility that a girl can get pregnant. This means that while having sex, sperm may have entered the vagina. Keep a watchful eye on if you get your period or take a home pregnancy test to be sure;
That's why every time a woman has sex, and isn't ready for a baby.
She should take EVERY known precaution to keep herself safe.
Use a Condom & Birth Control. No matter what there can always be a possibility of getting pregnant. Not everything you do is fool proof. It's just one BIG gamble.