During the scene where the lady is leaning into the car to tell him about the "funeral" there are a couple of people walking in the background. The same pair walk out past the bushes two times within 30 seconds or so.
When Phoebe is born David notices her defects. He mentions "mongoloid" babies, and they show a hand with deformed fingers as one of her defects. In all other shots with Phoebe she has normal hands.
Towards the end of the movie, in the scene where Paul and Phoebe finally meet, Phoebe offers her left hand to shake Paul's, who responds with his left. When the camera angle shifts, Paul and Phoebe are shaking with their right hands.
Every time David is taking a picture and we see the shot as he takes it, the "microprism" proves to be just an overlay and doesn't break up the image when out of focus.
When Nora and Paul go to see Caroline and meet Phoebe, everyone is wearing coats and gloves. But when Phoebe gives Caroline the flowers, she says "Happy Mother's Day". Mother's Day is in May. So the weather should've been warm enough that coats and gloves shouldn't have been necessary.
When Caroline is placing the money that she had received from David in the cookie jar, the twenty dollar bill that she puts in was actually produced in 2006 and would not have been available during that time.
When Nora and David are arguing in the kitchen and laundry room, Nora is shown using a modern style front load washing machine.
The neon OPEN sign in the window of the store Caroline buys baby supplies is too new, not of the period the movie first starts out in.
The exhaust fan over the stove in Caroline's apartment is not one of the period, it was too new.
When David and Phoebe get off the bus, a sign for Dalhousie University is clearly visible in the background. The scene supposedly takes place in Pittsburgh, PA, USA but Dalhousie is in Halifax, NS, Canada.