Once a girl has her period she can get pregnant any time she has unprotected sex. In the days before a girl ovulates, she is even more likely to get pregnant. Ovulating is when a mature egg is released from her ovary, and is pulled into her fallopian tube where it can be fertilised by sperm.
This happens 3 – 17 days after the end of her period. When it happens depends on the length of the specific girl’s menstrual cycle and it can vary from month to month.
If the boy ejaculates in a girl’s vagina during sex, his sperm will move up the vagina into the uterus and then up her fallopian tubes. If his sperm finds an egg there, they will fertilise it. The fertilised egg (or zygote) is moved down the fallopian tube to the uterus, where it implants itself into the lining of the uterus.
Once implantation has taken place we say that she is pregnant. In this case, she will miss her period. If a girl misses her period, she can do a home pregnancy test or visit a clinic to check if she is pregnant.
If the egg is not fertilised, the hormones that were building up the lining of the uterus go down. The thick lining then breaks down and the girl’s period will start (blood, mucous and tissue will flow from her vagina).
A girl can get pregnant even if she has sex when she:
- is having her period
- has not had her first period yet
- does not have an orgasm
- does not have sex very often
- urinates right after sex
- douches (squirts water up her vagina) right after sex
- tells her guy to pull his penis out of her vagina before he ejaculates
- jumps up and down after sex
- is under 12
- has sex for the first time
- has sex while standing up
If you have sex without using protection (condoms or other contraception), you can get pregnant. Pregnancy can happen if the sex is wanted or unwanted. It can even happen if you have sex just once. Condoms are the only method that can protect against pregnancy, STIs and HIV.
Pregnant by accident? Find out what to do below.