You should never smoke, do drugs or drink alcohol at all if your trying for a baby, pregnant or after you give birth.
Before you r pregnant.
In some states he you have it in your system they will call protective services. You should stop when you find out you are pregnant.
You should not have been smoking it at all but as soon as you find out you are pregnant you should leave it alone, don't even smoke cigarettes when you are pregnant, nothing that could harm or alter your babies developement...the best to you