Transplacental carcinogenesis

ELI5: Sometimes a mommy's tummy can have bad things in it, like germs or chemicals that can make a little baby sick. Sometimes these bad things can even cause cancer. This is called transplacental carcinogenesis. It happens when something bad goes from the mommy's body through a special connection called the placenta and into the developing baby’s body. It is important for mommies to take good care of their bodies during pregnancy to keep their baby healthy.