In both the Angel episode "Expecting" and the Torchwood episode "Something Borrowed," main characters wake up 8 1/2 months pregnant after a night out drinking with friends. In "Something Borrowed," Gwen is bitten on the arm by a carnivorous shape-shifting alien she and her partner are hunting. That bite transfers eggs to her bloodstream which move to her uterus and begin to grow—quickly. Though the alien who bites Gwen is killed, its mate tracks down Gwen, intending to tear the eggs from her when they are mature. Oh, by the way, this is all happening on Gwen's wedding day.
In "Expecting," the demon womb invasion happens via traditional human sex; the demon uses human males (who are in on the plot) as vehicles to impregnate human women. After sex with the man she is dating, Cordelia wakes up with seven little demons in her uterus. This also happens to the friends she was out with the night before and several other women.
Gwen is allowed more agency than Cordelia throughout the respective episode, though this would be true in many episodes of the shows. Cordelia's pregnancy is also a vehicle for the demon "father" to control both her mind and her body through a "psychic umbilical cord," while Gwen retains control. The solution to each pregnancy is to destroy the alien or demon who caused it. While Cordelia (under the mental influence of the demon) waits passive in a white gown while her two co-workers kill the demon, she does get to play a small part in its destruction: once it has been frozen to death with liquid nitrogen, she swings the pulley that smashes it to bits. Gwen devises a plan to kill the demon (using her wedding bouquet to conceal a gun) but the demon doesn't die. In the end, her male boss kills it and her husband destroys the eggs.