Getting a baby is a revolution within a marriage. Some people finally grow up with a baby. Most of them declare birth to be one of the most important moments of their life. Often enough a baby is the ultimate test for a marriage.
Anyhow babies lead to a different life for a few years. You have to be responsable for more than your own life for the rest of your life. Any other thinking of this new situation seems not to be normal. And all of a sudden your marriage is different.
So you have to deal with this new situation, and that one-man-one-woman-thing is over. It’s a hard thing for guys to realize that. And it’s open to fortune if that former romantic situation comes back when those babies try to live their own lifes around 20 years later.
Women deal with other changes in the meantime:

