I need help finding a movie title?

I only remember bits and pieces, maybe a little of my imagination thrown in. I remember this guy finds a woman and child (possible car crash) and takes them to a hospital. The wife of this man is pregnant and she is home when the hospital calls asking for (can't remember the REAL name so) Mr. Smith. Mrs. Smith says that he isnt home and what do they need. The hospital tells her that his wife is something (i forget the rest)... Anyway the story continues with the wife (Mrs. Smith for arguements sake) believing that Mr. Smith is having an affair. The only way he can prove he isn't the father of the other womans child is by having a DNA test. So he has the DNA tests and the results are negative. However Mr. Smith is told that he has some sort of irregular chromosomes to where he does not have the ability to impregnate a woman. So now going back to Mrs. Smith (who as I mentioned before is pregnant) was hiding this secret all along. Anyhow, I didn't watch the movie the whole way through, and I know I forgot a lot of things, but if someone could please help me I would greatly appreciate it, thank you.