Star Trek: Voyager - Season 2 Episode 21 -

A "spatial scission" causes Voyager to be duplicated. One of the Voyagers is under heavy attack from the Vidiians while the other remains impervious. Both Captain Janeways work together and agree to sacrifice one ship to save the other. Before self-sacrifice, the doomed Voyager sends its version of Ensign Kim and newborn Naomi Wildman to the other ship to replace the Kim that was killed in the attack and the baby who died from complications shortly after birth.