Whether it’s you or your partner that uses marijuana, it’s bad for fertility. A study at the University at Buffalo School of Medicine and Biomedical Sciences in New York found that the sperm of men who smoked marijuana had difficulty reaching an egg. The real surprise: the researchers say the same effect on sperm was noticed even if it was the woman who had smoked marijuana. The reason is that THC, the active ingredient in the drug, would be present in her reproductive fluids, as well, and would harm the sperm’s biological pathway to her eggs. Abstaining from the drug for three months allowed men’s healthy sperm to regenerate.