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Chorionic villus sampling - series

Normal anatomy

Normal anatomy

Chorionic villi are microscopic projections that line the chorion, the outermost layer of the embryonic sac. Surgeons sample these projections for genetic testing because they contain the same genetic material as a fetus.

If you are at risk for delivering a baby with genetic abnormalities, your health-care provider may recommend this prenatal test, which is performed at 10 to 12 weeks gestation to find out a fetus' genetic makeup.

Update Date: 5/31/2012

Updated by: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Bellevue, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.

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