Plot hole: In the episode "10,000 Steps," the parents from Amy's case say they adopted their first son Daniel when he was 3 because they thought they couldn't have biological children. Howeve,r the birth of their other son Seth proved that theory wrong. But Daniel is 13 and Seth is 12, so when Daniel was 3, Seth would have been 2 already.
Continuity mistake: In the end when they are in the hospital and Amy is talking with Stu about the proposal, in all the shots Amy's necklace is on the outside of her shirt. Then Peter comes in to tell them about the birth and Amy walks over to him and embraces him. In the shot right after the hug the necklace is inside her shirt, although she didn't have time to put it inside.