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Down Syndrome Screening in Assisted Conception Twins: An Iatrogenic Medical Challenge

Ben-Ami, Ido MD, PhD*; Maymon, Ron MD; Svirsky, Ran MD; Cuckle, Howard PhD§; Jauniaux, Eric MD, PhD, FRCOG

Obstetrical & Gynecological Survey: November 2013 - Volume 68 - Issue 11 - p 764–773
doi: 10.1097/OGX.0000000000000001
CME Articles: Down Syndrome Screening in Assisted Conception

Objective The objective of this study was to provide a critical analysis of the impact of assisted conception on prenatal screening for Down syndrome (DS) in twin pregnancies and the value of various screening modalities for early detection of anomalies.

Methods The literature was searched using PubMed and the Cochrane Library focusing on prenatal screening and antenatal care of assisted-conception twin pregnancies.

Results Serum screening alone is of limited value in detecting aneuploid twins, because the unaffected cotwin can “mask” the abnormal serum results of an affected one. In addition, this test can designate the pregnancy as at high risk but not identify the affected fetus. Nuchal translucency (NT) screening is the best available modality and a highly effective screening method for twin pregnancies. Among twins, NT alone has a 69% DS detection rate, first-trimester combined NT and serum biochemistry has a 72% DS detection rate, and an integrated screen will have an 80% DS detection rate at a 5% FPR. The data in the literature concerning the effect of assisted conception on maternal serum screening markers in twin pregnancies are scarce.

Conclusions Down syndrome screening in assisted-conception twins presents clinical and technical challenges. Therefore, assisted-conception twins need close monitoring from conception to delivery, by a practitioner familiar with the available screening modalities and their relative accuracy.

Target Audience: Obstetricians and gynecologists, family physicians

Learning Objectives: After completing this CME activity, physicians should be better able to identify the problems associated with prenatal diagnosis of Down syndrome in twins in general, and in assisted reproduction technology–conceived twins in particular, and perform the screening tests for spontaneous and assisted reproduction technology–conceived twin pregnancies, including identifying their diagnostic accuracy and pitfalls.

*Senior Lecturer, Infertility Clinic, †Professor, Director US Unit, ‡Senior Physician, Department of Obstetrics and Gynecology, Assaf Harofeh Medical Center, Zerifin, Israel, Affiliated With the Sackler School of Medicine, Tel-Aviv University, Tel-Aviv, Israel; §Adjunct Professor, Department of Obstetrics and Gynecology, Columbia University School of Medicine, New York, NY; and ¶Professor, Institute for Women’s Health, Royal Free and University College London Medical School, London, United Kingdom

All authors and staff in a position to control the content of this CME activity and their spouses/life partners (if any) have disclosedthat they have no financial relationships with, or financial interests in, any commercial organizations pertaining to this educational activity.

Correspondence requests to: Ron Maymon, MD, Department of Obstetrics and Gynecology, Assaf Harofe Medical Center, Zerifin 70300, Israel. E-mail:

© 2013 by Lippincott Williams & Wilkins.