Hesperian Health Guides
The Reproductive System in People Who Can Cause Pregnancy
People who can cause pregnancy include men and boys with the body parts recognized as male at birth, as well as some people who do not identify as either men or women, and transgender women and girls. Like people who can get pregnant, they have reproductive organs on the outside and inside of their bodies, and the size, shape and color of the outside parts may differ for each person.
People who can cause pregnancy do so by making and delivering sperm. Sperm travel from the testicles through a tube where they become part of a fluid called semen. Semen comes out of the penis during sex, especially at climax. Each drop of semen has thousands of sperm, which are too small to see without a microscope. If sperm enters the vagina of a person who can become pregnant, it can combine with an egg to cause pregnancy.