I generally don’t like to scare people but sometimes it’s necessary. When a mother-to-be inhales cigarette smoke, her womb fills with carbon monoxide, nicotine, tar, and other gunk that keep the baby from getting the oxygen and nutrients he needs. Sounds healthy, doesn't it? Your wife’s smoking increases the risk of low-birth-weight babies, miscarriage, and Sudden Infant Death Syndrome (SIDS).

A note to expectant dads who smoke: If you think your baby is somehow protected by being inside your partner, you're seriously mistaken. Recent research indicates that second-hand smoke may be just as dangerous to your pregnant wife and unborn baby as first-hand smoke.

As far as alcohol goes, complete abstinence is the safest choice. Your wife’s doctor may sanction a glass of wine every once in a while to help her relax. But one binge, or even just a few drinks at the wrong time (such as when the baby's brain is developing) can cause fetal alcohol syndrome, a set of irreversible mental and physical impairments. Even moderate social drinking has been linked to low-birth-weight babies, learning disabilities, and miscarriages in the early stages of pregnancy.

Bottom line: if you’re a smoker, quite now. And do everything you can to encourage your wife to immediately stop smoking or drinking. (Stay away from any and all over-the-counter drug options, though, without her doctor’s okay.) It’s tempting to avoid the whole issue out of fear that nicotine or alcohol withdrawal might lead to some marital tension. Bad choice. The potential danger to your baby far outweighs the danger to your relationship. If your wife doesn’t respond positively to your efforts, call her doctor. Chances are he’ll have some pretty strong words for her. He may also be able to offer some prescription assistance.