Is the blood that comes down after a miscarriage at six weeks gestation to be considered menstrual blood, and if not, how does the wife make up for the prayers she missed over a period of three days?

This blood is Istihadah (definition) (irregular bleeding) unless it coincides with the regular menstrual period, in which case it is Hayd (menstruation). It is not Nifas (definition) (post-natal bleeding) unless the creation of a human is evident in it after more than eighty days. She must make up the prayers she missed, having thought it was Nifas blood. The make-up prayers should be performed immediately, according to her capacity, in a way that does not cause her harm.