“…This confirms our observation in earlier studies (Ferguson-Smith and Ferguson-Smith, 1970) that amniotic specimens obtained before 14 weeks and possibly after 30 weeks are less satisfactory than specimens obtained at 14 to 30 weeks. This is probably related to the low cell count in early pregnancy and the large number of anucleate cells in later pregnancy (Votta et al, 1968;Wachtel et al, 1969).…”