The sperm and uterus work together to move the sperm towards the fallopian tubes. If an egg is moving through your fallopian tubes at the same time, the sperm and egg can join together. The sperm has up to six days to join with an egg before it dies. When a sperm cell joins with an egg, it's called fertilization.

How does the sperm fertilize the egg?

As they travel through the fallopian tubes, sperm gain the ability to fertilize an egg (1). They undergo two processes: capacitation, where its outer layer is changed, and hyperactivation, which changes the way the sperm's tail moves (1,5).

Can I get pregnant by just rubbing?

The same thing goes for body rubbing: It can't cause pregnancy unless partners have their clothes off and ejaculate or pre-ejaculate gets in the vagina or on the vulva. Oral sex can't cause pregnancy, regardless of which partner is giving or receiving it.