What’s the halacha concerning Moch dachuk after pregnancy, what are the basic gedarim binogaya this halacha?
This is something that has to be asked to a rov on an individual case by case basis. The basic rule regarding a moch dachuk is that it is mandatory if the woman started to bleed that day. Otherwise it is a strongly recommended preference. The difference is, depending on the specific case, if there is reason to fear that the moch will cause her to get irritated and bleed, as a result then we can forgo the moch. Often a woman after birth the area will be sensitive, especially if there stitches etc. and if she didn’t start bleeding that day we can be maikel. But again, one should not decide this on his own.
Y:D 196-1&2, Igros Moshe Y:D 2-79, Banyan Bayis Neeman 4 ftnt. 8.