The movie must be from the 80's maybe early 90's. All I can remember is that it is about a group of people (women and men, young as far as I can remember) wandering through a desert in some kind of post-apocaliptic scenario. One of the girls from the group is trapped inside a cave (chained?) on a rock and raped by a monster (mutant?). The rest of the group finds some kind of scientific-research base and they are killed one by one by the offspring of the girl and the mutant.
Maybe The Terror Within, (1989)?
In a post-apocalyptic future, human survivors are fighting a group of mutant monsters they refer to as "Gargoyles". Two of these survivors Michael and John are out surveying the world after a chemical or biological attack which left a large portion of the population mutated or dead. The survivors are part of the Mojave Lab and have lost contact with their sister Rocky Mountain Lab. Over the radio Sue and David hear John and Michael fall under attack from the gargoyles while investigating a large group of buzzards. In order to find John and Michael, David and Linda go out of the bunker but find John and Michael dead. They also find a live girl named Karen who they bring back to their bunker. While under anesthesia Karen gives birth to a gargoyle which gets loose in the bunker.
These creatures reproduce quickly by raping human women and impregnating them. The gestation period is short and deadly.
Sounds a bit like Humongous No raping monster though.