First-trimester screening with nasal bone in twins.
OBJECTIVE
The purpose of this study was to evaluate the Down syndrome detection rate at a 5% screen positive rate in first-trimester screening for twins.


METHODS
This was a retrospective study from August 2005 to July 2007 of twins who underwent first-trimester screening with nuchal translucency, nasal bone, pregnancy-associated plasma protein-A, and free beta-hCG. Risks were calculated on the basis of the Fetal Medicine Foundation twin algorithm. The model simulated distributions of unaffected and affected cases at 12 weeks of gestation.


RESULTS
Two thousand ninety-four twin pregnancies (4188 fetuses) met the inclusion criteria. The addition of nasal bone to nuchal translucency, pregnancy-associated plasma protein-A, and free beta-hCG increased the Down syndrome detection rate from 79-89% at a 5% screen-positive rate.


CONCLUSIONS
In twins, first-trimester screening with nasal bone is valuable. The improved Down syndrome detection rate can help these high-risk patients with the decision-making process of whether to pursue invasive testing with its associated pregnancy loss risk.
Cleary-Goldman
Jane
J
Mount Sinai Medical Center, New York, NY, USA.
Rebarber
Andrei
A
Krantz
David
D
Hallahan
Terrence
T
Saltzman
Daniel
D
D000328:Adult; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000097:blood; D004314:Down Syndrome / Q000175:diagnosis* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008423:Maternal Age; D048208:Nuchal Translucency Measurement; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011266:Pregnancy-Associated Plasma Protein-A / Q000032:analysis; D012189:Retrospective Studies; D014427:Twins
D018997:Chorionic Gonadotropin, beta Subunit, Human; D011266:Pregnancy-Associated Plasma Protein-A