Quoting Lydia Joy Serafino:" I was driving and started choking, and went to take a drink. My sister who was in the passenger seat ... [snip!] ... one, so I am probably a bit paranoid, but I just want him to be born healthy and safely. Thanks for advice and helpful tips."
It won't effect the baby. I have read a lot of articles and medical reports and studies because my doctors prescribed me medical marijuana for my chronic pain and insomnia. Everything I have read that has done ACTUAL studies with pregnant mothers, shows that the ONLY difference between clean mothers and the mothers that smoked REGULARLY (4 joints a week or more I think it said) was that the "pot babies" were more reactive to the newborn tests, more social, less likely to have anxiety and cry for no reason, and slept better.
So I would NOT worry about a little contact stuff one time