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Screening for Aneuploidy in Twin Pregnancies: Maternal Age- and Race-specific Risk Assessment Between 9–14 Weeks

Published online by Cambridge University Press:  21 February 2012

Anthony O. Odibo*
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA. [email protected]
Mohammed H. Elkousy
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA.
Serdar H. Ural
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA.
Deborah A. Driscoll
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA.
Michael T. Mennuti
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA.
George A. Macones
Affiliation:
Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, Philadelphia, USA.
*
*Address for correspondence: Anthony O. Odibo, MD., Division of Maternal Fetal Medicine and Genetics, University of Pennsylvania Medical Center, 2000 Ravdin Courtyard, 3400 Spruce Street, Philadelphia PA, USA.

Abstract

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The aim of this study was to calculate the risk for aneuploidy in twin pregnancies between 9–14 weeks utilizing maternal age, race and dizygotic twinning rates. Using previously published risks for aneuploidy in singletons and twins at the time of amniocentesis and at term, we calculated new risk estimates for twins at 9–14 weeks gestation or at the time of chorionic villus sampling. Using these tables, the risk for trisomy 21 in at least one fetus of a twin gestation in a 32-year-old at 9–14 weeks is 1/285 for Whites and for African- Americans. This is equivalent to the risk for trisomy 21 (1/265) in a 35-year-old woman with a singleton at the same gestational age. The risks for trisomies 18 and 13 also follow similar trends. In counseling women with twin pregnancies at the time of first trimester nuchal translucency screening or chorionic villus sampling, it should be noted that the maternal age-related risk for aneuploidy for a 32-year-old is equivalent to that of a 35-year-old woman with a singleton gestation.

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Articles
Copyright
Copyright © Cambridge University Press 2003