I think she would have been too emotional to stay there and act like nothing was wrong. She would have told someone about the affair.
I think she did not know about his philandering, because he liked it that way. His "telling her was the right thing to do" was BS. It would have upset her possibly enough to have caused her to go into labor early. He is a proven liar. He wants people only to know what they HAVE TO KNOW about him. He is only talking now because he HAS TO.
He thinks he can get away with this. I pray we prove him wrong.
And it crossed my mind that she may have gone into labor right then and there, as whatever happened to her happened. I wonder if there's more than blood that had to be cleaned up.