Vol. 19: Spring 2001
Prenatal Diagnosis
Prenatal Diagnosis in the Future
It is likely that future advances in ultrasound and other technology will continue to increase the number of options for less invasive and thus less risky prenatal diagnostic procedures. Already, some conditions that were first diagnosed using fetoscopy (high risk visualization of the fetus with an endoscope) may now be diagnosed using ultrasound, in some cases as early as the first trimester.
Isolation of fetal cells from the maternal circulation represents a promising approach to noninvasive prenatal diagnosis. An international multicenter trial sponsored by the National Institutes of Health is currently being conducted to assess the diagnostic efficacy of using fetal cells in maternal blood to detect fetal chromosome disorders. Preliminary data suggest that the sensitivity is 40-50%.
There have been significant advances in screening for Down syndrome in the first trimester using nuchal translucency and measurement of serum pregnancy-associated plasma protein-A (PAPP-A) and free (-hCG levels. Detection rates for Down syndrome have been estimated to be between 72 and 87%. If first trimester noninvasive screening techniques prove accurate, it is possible that patients with reassuring screening results will elect not to proceed with invasive prenatal diagnosis procedures. Alternatively, if patients at increased risk for fetal chromosome disorders have reassuring first trimester screening, they may choose to delay prenatal diagnosis until the second trimester and avoid the potential increased risks associated with CVS and early amniocentesis compared to second trimester amniocentesis.
It is important to maintain a close working relationship with your local genetic center offering prenatal diagnosis to assist you in offering your patients the most up-to-date information in this rapidly changing field. With the sequencing of the human genome nearly completed, we will see continued expansion in the number and types of tests available. Information on services available in the Mountain states region can be obtained via the MSGF Directory of Genetic Services or by contacting the regional coordinator, Joyce Hooker at (303) 692-2423.
References (extensive references available upon request)
Lam YH, Tang MH, Lee CP, Tse HY.1999. Prenatal ultrasonographic prediction of homozygous type 1 alpha-thalassemia at 12 to 13 weeks of gestation. Am J Obstet Gynecol 180:148-150.
Shackleton CH, Roitman E, Kratz LE, Kelley, RI.1999. Midgestational maternal urine steroid markers of fetal Smith-Lemli-Opitz (SLO) syndrome (7-dehydrocholesterol 7-reductase deficiency). Steroids 64:446-452.
The Genetic Drift Newsletter is not copyrighted. Readers are free to duplicate all or parts of its contents. The Genetic Drift Newsletter is published semiannually by the Mountain States Regional Genetic Services Network for associates & those interested in Human Genetics. In accordance with accepted publication standards, we request acknowledgement in print of any article reproduced in another publication. The views expressed in the newsletter do not necessarily reflect local, state, or federal policy. For additional information, contact Carol Clericuzio, M.D., Editor, Department of Pediatrics, The University of New Mexico, Albuquerque, NM, 87131
Prenatal Diagnosis - Table of Contents
Introduction
Prenatal Diagnosis of Single Gene Disorders
Down Syndrome Maternal Serum Screening
Fetal Ultrasound
Amniocentesis
Chorionic Villus Sampling
Percutaneous Umbilical Blood Sampling
Preimplantation Genetic Diagnosis
The Future of Prenatal Diagnosis
TABLE: Timetable for Prenatal Diagnostic/Screening Procedures
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