False Positive certainly isn't the first film to exploit pregnancy for a good bout of horror. There are quite a few films out there that use looming parental fears and hormonal changes as a premise for paranoia and general nastiness, John Lee doesn't really add much to them, I'm afraid.
Lucy and Adrian are trying to get pregnant, but their attempts are futile. Adrian contacts Dr. Hindle, an old friend and respected fertility doctor, who agrees to have them over. Not much later Lucy is pregnant, but what should be a happy pregnancy quickly turns into a nightmare, as Lucy starts to suspect something is off with Hindle.
The film has its moments, but the finale (with its inevitable twist) is a bit too basic. The performances are decent, and the cinematography is decent, Lucy's character on the other hand is more than a little drab, which doesn't make it easy to care for her predicament. Decent horror filler, but not quite as nifty as it tries to be.