It's a generally accepted fact that women should quit smoking and drinking while pregnant. But it's helpful for dads-to-be to quit as well. Not necessarily because of second-hand smoke (though that's a danger as well), but mainly because when one partner continues the unhealthy habits it makes it all the harder for the other to quit. If dad continues to smoke and/or drink it's harder for mom to quit and she's more likely to pick the habits back up after childbirth.

Researchers studied hundreds of expectant moms' and dads' substance abuse over a three-year period (including pregnancy). Their findings include:

• 77% of female cigarette smokers and 50% of marijuana smokers used those substances to some degree during pregnancy; only 38% and 24% respectively reported cigarette or marijuana smoking.
  
• Overall rates of smoking and drinking declined during pregnancy, but picked back up within six months after childbirth.