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First-trimester combined screening for trisomy 21 at 8-13 weeks.
Wright D, Spencer K, Kagan K, Tørring N, Petersen O, Christou A, Kallikas J, Nicolaides K.
Ultrasound Obstet Gynecol 2010;36:404-11. -
Two-stage first-trimester screening for trisomy 21 by ultrasound assessment and biochemical testing.
Kagan K, Staboulidou I, Cruz JJ, Wright D, Nicolaides K.
Ultrasound Obstet Gynecol 2010;36:542-7.