 Approximately one in six couples are unable to conceive after a year, despite trying interlabeled infertile. And in up to half the cases, it may be the man's fault. There are several lifestyle factors that have been associated with diminished sperm production, such as smoking cigarettes. What about smoking marijuana? Regular marijuana smoking, more than once a week, was associated with about a 28% lower sperm concentration and lower total sperm count, based on a study of more than 1,000 men. But no adverse association was found for irregular use, meaning less than once a week. Now this wasn't a randomized study, and so there may have been other factors that go along with regular marijuana use that could have really been to blame, but they took into account cigarettes and alcohol and other drugs and STDs and things like that. But there's always a possibility there's something else for which they didn't control. Findings were similar for women. Hundreds of infertile couples were studied in California, and just like men had about a quarter fewer sperm, a quarter fewer eggs were retrieved from women using cannabis more than 90 times in their lifetime, or using the year before. Again, there could have been confounding factors, but until we know more, couples that are trying to conceive may want to make the joint decision to turn over a new leaf. What about during pregnancy? Medical authorities recommend that women even contemplating pregnancy should be encouraged to discontinue marijuana use and not use during pregnancy or lactation, although the Academy of Breastfeeding Medicine suggests the known benefits of breast milk currently outweigh any potential harms for women who continue to smoke it. Despite these warnings from authorities, the use has increased among pregnant women in recent years, up 60%, but that's only from about 2.5% up to less than 4%, less than half the frequency of non-pregnant women. Why are OBGYNs so down on getting high? You'll see scary articles in the American Journal of Obstetrics and Gynecology making claims like this. A large study supposedly documenting a significantly increased risk for a serious birth defect. But if you don't just take their word for it and pull up the actual study, you'll see that the association wasn't statistically significant after all. Objective education about marijuana in pregnancy is good, but biased education is not. There have been some risks identified. Infants may be more likely to be born anemic or have a lower birth weight or require intensive care compared to infants and mothers who do not use marijuana. But it's difficult to determine the direct effects of maternal cannabis use on the developing fetus because of a variety of confounding factors for which studies may not have been able to completely control. Studies also show links between prenatal marijuana exposure and learning problems later in life, manifesting years later at school. That's really where the greater concern lies. The potential long-term effects on brain development. And so, even after weeding out the myths, there is enough concern that pregnant and breastfeeding women should indeed probably be advised to either decrease or, where possible, cease cannabis use entirely.