It's Alive (2008)

When Lenore becomes pregnant during her final semester at grad school, she quits to go live with her boyfriend Frank and his younger brother. After going to the hospital in pain, doctors tell Lenore that they will have to deliver the baby early as it has doubled in size since the last appointment.

During the delivery, the baby and mother are fine, but everyone else in the operating room is killed. The police want to talk to Lenore to see if she can remember anything that might help them catch the killer, but she is uncooperative.

Once the baby comes home, Frank is oblivious to it's odd behavior, his younger brother is scared of it, and Lenore is just plain annoying and stupid. She finds the baby outside eating a pigeon and her reaction is, "No! No! Don't eat that!" How about wondering how the baby got out of it's crib, made it outside and got hold of the pigeon?

Also when she finds the baby gnawing on a dead bunny in it's crib, she takes the bunny away and doesn't say a word to the baby. When the psychiatrist is killed in an unbelievably violent scene, she just drives his car into the lake. Yikes lady, no mention of any of this to your husband? Eeeek!