Any time grown-ups have sex, it's possible that they can make a baby. Sometimes, people have sex because it feels good to their bodies, even though they don't want to have a baby. Because a baby is made inside a woman's body during sex, when a man's sperm is joined with the woman's egg, it can be very hard to predict if the woman will become pregnant, so sometimes she can become pregnant accidentally.
If a man and woman want to have sex but don't want to make a baby, they can use special kinds of protection to help prevent the sperm and egg from joining up. When a man and woman don't use protection during sex, the woman has a very high chance of becoming pregnant. That's why sex is a big decision. People need to be responsible and make smart choices if they decide to have sex even though they don't want to have a baby.
There are lots of different kinds of protection grown-ups can use if they want to have sex but don't want to make a baby. For example, women can take a pill that prevents them from releasing eggs. Men can use something to catch the sperm when it comes out of their penis, so that it's unable to find and join the woman's egg. These kinds of protection are called "birth control," and it's very important to use them if someone does not want to have a baby.