womb

Definition:

The term "womb" refers to where a baby grows inside its mother.

This is an older term that is sometimes used in order to be polite and less direct. (See: euphemism)
A more modern term for womb is "uterus."
Some languages use a word like "belly" to refer to a woman's womb or uterus.
Use a word for this in the project language that is well-known, natural, and acceptable.