I never did get that whole immaculate conception dogma from the catholics . The bible says mary had found favor with God not that she was sinless or perfect . I don't know if it was mosaic law that a man could not have sex with a pregnant wife or what but I agree the gospel states that he did not have sex with Mary until she was ready for more babies . I think that was pretty much the law anyway that sex could only be for that purpose . That's why horny king solomon had all those concubines .