We were six weeks pp. the night before our ds went in for his second open heart surgery. Bit like Charlotte, I think we both needed the closeness and to feel something other than fear and grief. I think we both thought we would lose him the next day. Bit like people having sex after a funeral- just a need to stop feeling emotions. I think 6 weeks was the advice we were given as well.
My OB has always advised that you try a few days before the six week check so he can check out any issues etc.