What's Up With the Twist Ending of em False Positive /em , Ilana Glazer's Pregnancy Horror Movie?

This article contains spoilers for the entirety of False Positive. In False Positive, the phrase "mommy brain" begins almost as a joke. As Lucy (Ilana Glazer, who also co-wrote the film) and Adrian (Justin Theroux) try--and then finally succeed, thanks to Dr. John Hindle (Pierce Brosnan)--to get pregnant, the words, initially used to refer to a strong rush of maternal instinct, take on an increasingly sinister timbre. Is it really just "mommy brain" that's causing Lucy to become suspicious of Hindle, or is the term being used to gaslight her? The final answer seems to be: a little bit of both.