The Switch.

Kassie is a smart, fun-loving single woman who, despite her neurotic best friend Wally’s objections, decides it’s time to have a baby – even if it means doing it herself… with a little help from a charming sperm donor. But, unbeknownst to her, Kassie’s plans go awry because of a last-minute switch that isn’t discovered until seven years later… when Wally gets acquainted with Kassie’s cute, though slightly neurotic, son.