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An expansive menu of prenatal tests for Down syndrome (DS) is already available to pregnant women around the globe, but new tests are likely to become the most popular entrées. Presently, pregnant women can choose among the many prenatal screening tests – triple screen, quadruple screen, first-trimester combined screen, stepwise sequential screens, and fully integrative screens – to receive statistical chances that their fetuses have DS, to varying degrees of detection (table 1).1 For a definitive prenatal diagnosis of DS, however, women currently have just two options, both of which are invasive: chorionic villus sampling (CVS), generally performed between 9 and 12 weeks of gestation, and amniocentesis, traditionally offered between 15 and 20 weeks of gestation. By nature of being invasive, both of these diagnostic tests carry small, albeit real, risks of spontaneous abortions.2 3 4 5 6 7
Professional organisations in the USA – such as the American College of Obstetrics and Gynecology (ACOG) and the American College of Medical Genetics (ACMG) – and many similar organisations around the world such as the Fetal Anomaly Screening Programme in the UK now recommend that all pregnant women, regardless of age, be offered a selection of these available tests.8 9 10 11 Most pregnant women seeking prenatal confirmation of DS start with a prenatal screen, learn the statistical chances that their fetus has DS, and then decide whether to proceed with CVS or amniocentesis. Pregnant women in the UK seeking prenatal confirmation of DS typically start with one of these recommended screens, receive a result that is pre-interpreted as “high risk” or “low risk”, and are then offered CVS or amniocentesis only if they fall in the “high risk” category.
A forthcoming option, to be …
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