The characters say multiple times that Rebecca's birthday is on a Sunday; however, while they are in the ER they are able to call Naomi's doctor's office to ask about her test results. It is unlikely that a GP's office would be open on a Sunday.
Due to constraints in budget and scheduling towards the conclusion of principal photography, many shots involving Amy Poehler and Mya Rudolph throughout the climax scene that takes place on the hill had to be filmed and composited separate from the remainder of the cast. This is evident due to drastic changes in lighting on each actors faces between shots and errors in angle continuity between each character in the final product.