The uterus or womb was an organ of reproduction. It was the main female reproductive organ found in the anatomy of most mammal species. It was the organ in which a child would grow after conception until childbirth.
A rare complication in Ktarian/Human pregnancies is, if the mother is human, when the baby shifts position in the uterus during the birthing process and the exo-cranial ridges lodge in the uterine wall. If not resolved quickly, the uterus may rupture and result in internal bleeding and possibly even death of both mother and child. It is very painful for the mother and prevents the birth from taking place naturally. If this complication occurs, a fetal transport may be needed. (VOY: "Deadlock")
B'Elanna Torres described her simulations in EV suit at Starfleet Academy as feeling "peaceful, like floating in the womb," but described an experience of a real space walk as making her a little sick to her stomach. (VOY: "Day of Honor")