Experiment is definitely a fine addition to a 'Aliens need Women' list. It's also part of KU.
The Kealans have been on earth for years with no demands, until they force ordinary Isabella to marry Tairan. In the distant past humans were taken from earth and left on another planet. The Kealans haven't seen a live birth in 10 years. Rather than go extinct they determine that Isabella and Kealan are compatible. Neither one wanted to marry but they had no choice. They are at the whims of a sadistic scientist. His only goal is to study and eventually breed out any human DNA to revive the Kealan people. Tairan is one of the last fertile men and must try to get Isabella pregnant then she must battle the odds to stay pregnant. I liked both Isabella and Tairan. The story moved at a good pace. I thought the ending was a bit too HEA, otherwise a decent read.