Justifiability of amniocentesis on the basis of positive findings of triple test, ultrasound scan and advanced maternal age
Keywords:Chromosomopathy, Triple test, Ultrasound, Maternal age, Prenatal screening
AbstractObjective. To assess the effectiveness of antenatal screening for chromosomalabnormalities based on maternal age (≥35 years), positiveultrasound findings or a positive triple test. Materials and methods.Retrospective six-year study. The pregnant women routinely underwentestablished clinical and laboratory practice at the Departmentof Medical Genetics between 1997 and 2003. The women’s case noteswere examined to identify indications for karyotyping, gestation periodand the outcome of karyotyping and pregnancy. Results. Invasiveantenatal tests were performed on 1440 cases, 1168 (81.11%) age 35(a),72 (5.00%) positive triple test (b), 24 (1.67%) positive ultrasound scanning(c) and 176 (12.2%) other (psychological, personal reasons, etc)(d). The overall positive predictive value was 1.67% (1.6%(a), 1.4% (b),12.5% (c), 0.0% (d). The constructed model of logistic regression gavean odds-ratio of 8.647 for the “positive ultrasound result vs. maternalage ≥35” indication, while the odds-ratio for the triple test vs. maternalage ≥35 was 0.854. Conclusions. Amniocentesis and cytogeneticanalysis of foetal karyotype should be presented as a diagnosticpossibility to all women over 35 years. The application of biochemicalmarkers was far from the expected results. If we compare results forindication positive ultrasound scanning vs. maternal age, an oddsratioof ~9 was obtained. These results demonstrate that the likelihoodof obtaining positive results (i.e. the presence of chromosome alterations)from an amniocentesis having this indication is almost 9 timeshigher than from having an amniocentesis performed solely for advancedmaternal age.
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