Other mistake: Being a three time mom, I know that the sonogram that Susanne gives Nick at the beginning could not be hers, due to the fact that she just found out she was pregnant. The babies on that sonogram are too detailed. They have to be at least 30-35 week-old fetuses. At her stage, you would not be able to make out the baby.
Continuity mistake: Suzanne's pregnant belly goes up and down throughout the movie without any regard to her gestation. In one scene, Suzanne rests her arms on her stomach and the next "day" she's cooking in the kitchen with a flat stomach. It's as if the movie was heavily edited and no one paid attention to her.