With some states choosing to legalize marijuana, we hear very little of cannabis' effects on health, and even less on its impact on reproductive health. We have know for years that pot smoking can cause chromosomal breakage, and so for those couples trying to get pregnant, many reproductive specialists encourage both partners to quit when attempting pregnancy. Now, some new data out of the UK shows men who use marijuana are considerably more likely to have abnormally shaped sperm, Interestingly, in the same study, alcohol and tobacco did not. Since even in normal men, it is normal to have some proportion of misshapen sperm, this finding in itself is not enough information to say that marijuana causes infertility. Still, why take the chance? This is just another good reason to quit if you are planning to start a family in the near future.