Why do some husands get angry when they're informed their wife is pregnant?

A friend of mine got married to a man whom she says loves her very much. She told me during their engagement they talked about planning a family. They are very financially stable and well off so they both agreed that when it happened they would embrace it all the way. Eighteen months later ... and now she's pregnant. She said she couldn't wait to tell him. (Oh, by the way, because of their religious beliefs he was the one using the birth control, not her). Well, she told him - she said he argued with her as if he didn't want to believe what she was saying. He took her to their family physician to prove the ept she used was wrong. She said the doctor called and said the test was positive. Six months later in her pregnancy he braggs about it to his family and friends at work but when he gets home he's a different person - still saulking and always in a bad mood. I asked her what's wrong with him, she said the only thing she can think of is he doesn't want her to have this baby. She also said she tried talking to him about it and it would just make him more upset. She's trying so hard to be happy for her baby but he's making it very difficult for her to be. I call her and tell her to do something that'll brighten up her day. Like go to the park, watch other people's children how they laugh and play or go shopping - treat herself to something that'll lift up her morale. You know though, considering the fact that he's the one who decided to not use his rubbers and not consult her about it when he made that decision baffles me. In my opinion if anyone should be upset it should be her - his wife. Why do some men act childish and upset when they find out their wife is pregnant?