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First-trimester screening for trisomy 21 in singleton pregnancies achieved by assisted reproduction.
Liao AW, Heath V, Kametas N, Spencer K, Nicolaides KH.
Hum Reprod 2001;16:1501-4. -
Absence of nasal bone in fetuses with trisomy 21 at 11-14 weeks of gestation: an observational study.
Cicero S, Curcio P, Papageorghiou A, Sonek J, Nicolaides K.
Lancet 2001;358:1665-7.