. Evaluation of first trimester maternal serum and ultrasound screening for Down's syndrome in Eastern and Northern Finland. European Journal of Human Genetics (2001) 9, 404-408
. Chartier M, et al. Measurement of plasma chorionic gonadotropin (hCG) and CG activities in the late luteal phase: Evidence of the occurence of spontaneous menstrual abortions in infertile women, Fertil Steril 31:134,1979.
. Ashitaka Y, et al. Production and secretion of hCG andhCG subunits by trophoblastic tissue. In Segal S (ed):Chorionic Gonadotropins. New York, Plenum, 1980 p 151.
. American College of Obstetricians and Gynecologists. Medical Management of Tubal Pregnancy. Practice Bulletin Number 3, December 1998. Washington, D.C. ACOG, 1998
. Jenn HSU, et al. Urine Free Beta-hCG and Total Estriol for Down Syndrome Screening During the Second Trimester in an Asian Population. Obstetrics and Gynecology 1999, 94: 107-111
. Taipale Pekka, et al. Increased Nuchal Translucency as a Marker for Fetal Chromosomal Defects. The New England Journal of Medicine. Volume 337: 1654-1658. 1997