Down-Syndrom-Screening im ersten Trimenon

Zusammenfassung

Down-Syndrom ist die Ursache für ungefähr ein Drittel aller geistigen Behinderungen. Mit einer Prävalenz von 0,2 % aller Schwangerschaften und der Möglichkeit einer sicheren pränatalen Diagnostik mittels Chorionzottenbiopsie oder Amniozentese ist heutzutage jeder Gynäkologe während der Schwangerenbetreuung zur Beratung über Chromosomenanomalien aufgefordert. Die Basis bildet das altersentsprechende Risiko, und ein Hinzuziehen der quantifizierbaren fetalen Hinweiszeichen individualisiert die Risikoberechnung und verbessert die Entdeckungsrate für Down-Syndrom. Diese liegt bei einer Falsch-positiv-Rate von 5 % bei reinem Alters-Screening (Cut-off in Deutschland/Österreich 37 Jahre) bei 30 %. Modifiziert man das Risiko durch die Messung der Nackentransparenz und der Serumkonzentrationen von freiem β-human chorionic gonadotrophin (hCG) und pregnancy associated plasma protein-A (PAPP-A), steigt die Entdeckungsrate auf rund 90 %. Diese Information sollte heute jeder Schwangeren zugänglich gemacht werden.

Abstract

Down's syndrome accounts for roughly one third of all causes of mental handicap. It has a prevalence of 0.2 % of all pregnancies and, with the availability of prenatal diagnosis by chorionic villus sampling or amniocentesis, every obstetrician faces the challenge of counseling his patients about chromosomal abnormalities. Combining quantifiable fetal markers with the maternal age-related risk individualises the risk calculation and improves the detection rate of Down's syndrome. Thus, at a 5 % false-positive rate, the detection rate is 30 % for age-based screening (age cut-off of 37 years in Germany/Austria), and if the nuchal translucency measurement and maternal serum concentrations of free b-human chorionic gonadotrophin (hCG) and pregnancy associated plasma protein A (PAPP-A) are taken into account, the detection rate increases to about 90 %. This information should be provided to every pregnant woman.

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