Good evening, The use of marijuana during the period of conception is not recommended as it is linked to the risk of miscarriage, mental developmental delays in the child and low birth weight babies. It is essential that you are not exposed to second-hand smoke from marijuana. A recent study showed that when it is the man who smokes, it is not necessarily related to a delay in conception. I would recommend that you try as much as possible to limit your partner's cannabis use. Unfortunately, I have not been able to find a clear and reasonable time frame from my research regarding the cessation of consumption and the moment of conception to limit the risk of miscarriage.