Girls have what is called a hymen in their vaginas. The hymen can be broken by a girl exercising or playing sports rigorously, wearing a tampon or menstrual cup, or when she loses her virginity by having sexual intercourse. When this happens, some blood may come out of her vagina.
Girls can get pregnant if the male she is having sex with pulls his penis out before orgasm, because males can ejaculate some semen before reaching orgasm.
She can also get pregnant if it's her first time having sex, or if the male didn't reach orgasm at all. It is also possible for a girl to get pregnant if the male uses a condom, as sometimes condoms break or have holes in them.
A boy should never keep a condom in his wallet because the condom can get a hole or holes in it. Boys should only use a condom once and check the expiration date on the wrapper.
There are also other forms of birth control, such as the cervical cap, a diaphragm, birth control pills, the patch, an internal condom, or an implant.
