Ok. I haven't done extensive research on this particular aspect of Yeast Assassin as far as how long you should wait. Here is what I have researched and do know though.
From the reading I've done there are only two things in Yeast Assassin that are bad for a woman to take while pregnant and nursing. One is Black Walnut. It is used to dry up milk supply in some cultures during the weaning process. Not something you want to be taking while nursing! The other is Pau D'Arco. It is used to trigger miscarriages in some cultures (although in higher amounts than what is found in YA.)
Neither of these things have been indicated in any of the research I've done as "lingering" supplements as in staying in your system for any period of time at all. I know in order for it to be effective you have to take it a couple of times a day so it doesn't appear to have a long term effectiveness.
If anybody else has any further information please feel free to share!