with ds1 it was about 3mths or so, as i had an episiotomy and it was sore, we did do other things that were non penatrative tho and took it slowly.
ds2 2 wks, very easy birth and it felt fine, again took it slowly.
ds3 and ds4 i cant remember! but they were both easy births so within a month or two.
and dd, um again i cant remember, tbh tho sex is lower down on our priority list than sleep! and we have always been happy doing stuff that doesnt involve penetration, so we werent desperate to get back to penetrative sex as there are plenty of alternatives! but it was always when i was ready and i initiated it, dp was happy to wait, so no pressure.
re bleeding, i wouldnt do it when heavily bleeding, but do happily have sex on my period (not the first few days when flow is heavy) so same with childbirth, once i was not heavy etc and i wasnt worried about the mess etc.