Species II (1998)

After being infected during by an alien during a mission to Mars, an astronaut returns to Earth and seeks out his mate--the beautiful but deadly Sil. Astronaut Ross discovers that each time he has sex, the woman is impregated with an alien that kills her in childbirth. Sil wants to mate with Ross to produce a more perfect alien offspring, and the assassin hired to dispatch the aliens hopes that she will lead him to Ross and his violent offspring.