1. Maternal agespecific rates of 47, + 21 and other cytogenetic abnormalities diagniosed in the first trimester of pregnancv in chorionic illus biopsy specimens: comparison with rates expected from observations at amniocentesis;Hook, E.B.; Cross, P.K.; Jackson, L.; Pergament, E.; Brambati, B.;Am J'Hum Genet,1988
2. Screening for Down's syndrome;Cuckle, H.S.; Wald, N.J.,1990
3. Population Censuses and Surveys. Birth statistics;Office of,1989
4. Estimating a woman's risk of having a pregnancy associated with Down's syndrome using her age and sertim alphafetoprotein level. BrJ7 Obstet Gynaecol;Cuckle, H.S.; Wald, N.J.; Thompson, S.G.,1987
5. Mlaternal serum screening for Down's syndrome in early pregnancy;Wald, N.J.; Cuckle, H.S.; Densem, J.W.E.; Nattchahal, K.; Royston, P.; Chard'l', etal;BAM7