While pot hasn't been shown to hurt baby before (or even soon after) getting pregnant, it's definitely a good idea to quit as soon as you decide to conceive. Smoking pot while pregnant can affect the function of the placenta and may result in low birth weight and fetal distress during labor. Moreover, newborn babies of pot-smoking moms may go into withdrawal upon delivery (suffering side effects like the jitters and a slow response to stimuli, to name a few). If you ask us, it's better to kick the habit on your own, well before you add a baby into the mix.
But enough about you. Wondering how your partner's pot smoking could affect your conception chances? A study from the University at Buffalo has linked pot smoking to decreased sperm count and, shall we say, confusion among the sperm he's got. The study followed men who smoked 14 times a week for an average of 5.1 years and found that those who smoked were significantly more likely to have reduced sperm count than men who didn't. The study also found that smokers' sperm were swimming too fast too soon — their timing was off to successfully fertilize the egg. Because it takes a while for THC (the chemical in pot) to clear out of your body, it's hard to tell if men who've stopped smoking can get their boys back to a nonsmoker's state. But, regardless, these kinds of stats should make any dude think twice before picking up his next joint.