When exactly does a mother know her child is mongolian ..when intrauterine or after delivery?

Confusing question: If you are referring to a Down syndrome child the terms referring to "mongolism" have not been used in more than 4 decades.It was an archaic scientific idea that it represented a primitive form of human. Mothers will only know for sure if their baby carries this defect after delivery, unless prenatal chromosome studies are done on fetal cells.