First Trimester Risk Assessment for Down Syndrome: Practical, Ethical Considerations

Newswise — Risk Assessment for trisomy 21, also known as Down Syndrome (a condition in which there are three copies of chromosome 21 instead of two), can give parents and healthcare providers the critical information needed to prepare for the birth of a special needs child or make an informed decision about whether to continue a pregnancy. As diagnostic methods have evolved, both the accuracy and the ability to diagnose earlier in the pregnancy have improved.

In a study undertaken by investigators at the Harris Birthright Research Centre for Fetal Medicine, King's College Hospital, London and the Department of Clinical Biochemistry, Harold Wood Hospital, Essex, UK, and published in the June issue of the American Journal of Obstetrics and Gynecology, over 30,000 first-trimester pregnancies were screened for trisomy 21 using a combined regimen of maternal age, fetal nuchal thickness (NT), maternal serum-free beta-human chorionic gonadotrophin (ß-hCG) and pregnancy-associated plasma protein-A (PAPP-A).

These tests were carried out in a One-Stop Clinic for first-trimester Assessment of Risk (OSCAR). This multidisciplinary center performed biochemical testing of the mother, ultrasound examination of the fetus, and post-test counseling, all within a 1-hour visit to the center.

The detection rate of trisomy 21 and other major chromosomal defects by this method was about 90%, for a false-positive rate of 5%. This is far superior to the 30% detection rate achieved by maternal age. Furthermore, with first-trimester combined screening, the 65% detection rate for trisomy 21 associated with second-trimester screening with the use of maternal serum biochemistry, can be achieved with a more than 10-fold reduction in the number of unnecessary invasive tests, from 5% to 0.4%.

Dr. Kypros H. Nicolaides, senior author, stated "In our opinion, risk assessment for chromosomal defects in the first rather than the second trimester provides earlier reassurance for those with a normal result and less traumatic termination for those choosing this option." Based on this extensive study, the authors believe that "assessment of risk by a combination of maternal age, fetal NT, and maternal serum-free b-hCG and PAPP-A, followed by selective termination of affected fetuses reduces the potential live birth prevalence of trisomy 21 by at least 90%."

In a related article, the ethical considerations for using first-trimester risk assessment are discussed. Frank Chervenak, MD, and Laurence McCullough, PhD, consider the physician as a fiduciary, with a responsibility to safeguard the ethical principles of autonomy, beneficence and justice. Based on the professional virtues of integrity and self-sacrifice, obstetricians and specialists in risk-assessment have a strict ethical obligation to identify, manage and disclose both economic and non-economic conflicts of interest.

The study is reported in "Prospective first-trimester screening for trisomy 21 in 30,564 pregnancies" by Kyriaki Avgidou, MD, Aris Papageorghiou, MD, Renu Bindra, MD, Kevin Spencer, MD, and Kypros H. Nicolaides, MD. The discussion of the ethical issues is "Implementation of first-trimester risk assessment for trisomy 21: Ethical considerations," by Frank A. Chervenak, MD and Laurence B. McCullough, PhD.

These articles appear in the American Journal of Obstetrics and Gynecology, Volume 192, Number 6, published by Elsevier.

The American Journal of Obstetrics and Gynecology (www.ajog.org), known as "The Gray Journal," presents coverage of the entire spectrum of the field, from the newest diagnostic procedures to leading-edge research. The Journal provides comprehensive coverage of the specialty, including maternal-fetal medicine, reproductive endocrinology/infertility, and gynecologic oncology. It also publishes the annual meeting papers of several of its sponsoring societies, including the Society for Maternal-Fetal Medicine and the Society of Gynecologic Surgeons. The information contained in this article published in the American Journal of Obstetrics and Gynecology is not a substitute for medical advice or treatment, and the Journal recommends consultation with your physician or healthcare professional.

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Full text of the articles mentioned above is available upon request. Contact Rosemary Sheridan at 212-633-3741 to obtain a copy or to schedule an interview.

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