"Although men may not be aware of it, they actually undergo hormonal changes as they prepare for fatherhood, says neuropsychiatrist Louann Brizendine, author of The Male Brain (Broadway Books, $24.99), released in March. At first, those hormones tell them to panic, or at least pay attention. Levels of a stress hormone called cortisol — the same ancient chemical that instructs men to fight or take flight — tend to spike about four to six weeks after men learn they're going to be fathers, subsiding as the mother's pregnancy progresses, Brizendine says." - Kelly W.