Junior (1994)

Alex Hesse (Arnold Schwarzenegger) and Larry Arbogast (Danny DeVito) are working on a new drug which will reduce the chances of a woman's body rejecting her baby, and thus causing a miscarriage. When their research funding is withdrawn, and human experimentation is denied to them, they decide to test the drug by briefly impregnating Hesse. However, Hesse becomes attached to his unborn baby.