-
Screening for trisomy 21 in twins using first trimester ultrasound and maternal serum biochemistry in a one-stop clinic: a review of three years experience.
Spencer K, Nicolaides KH.
BJOG 2003;110:276-80. -
First trimester prenatal diagnosis of trisomy 21 in discordant twins using fetal nuchal translucency thickness and maternal serum free beta-hCG and PAPP-A.
Spencer K, Nicolaides KH.
Prenat Diagn 2000;20:683-4.