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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 maternal serum PAPP-A, SP1 and M-CSF levels in normal and trisomic twin pregnancies.
Bersinger NA, Noble P, Nicolaides KH.
Prenat Diagn 2003;23:157-62. -
Maternal serum free beta-hCG at 10 to 14 weeks of gestation in trisomic twin pregnancies.
Noble PL, Snijders RJ, Abraha HD, Sherwood RA, Nicolaides KH.
BJOG 1997;104:741-3.