In what organs do mammals carry babies?

The bearing of young in most mammals occurs in the placenta. The stage of bearing offspring from fertilization to birth is called intrauterine. It takes a person nine months. They are divided into three terms of three months. In the first trimester, the organism is called an embryo, and in the next two, it is called a fetus. But there are some exceptions among mammals. These are the platypus and echidna. They are the only mammals that reproduce by laying eggs. They are the most ancient mammals that live in our time.