[Ultrasound screening for Down's syndrome early in pregnancy: nuchal translucency thickness].

Screening for Down's syndrome (DS) in the Netherlands is based on maternal age. Women aged 36 years or above are offered amniocentesis or chorionic villus sampling to determine if the foetus has Down's syndrome or other chromosomal abnormalities. Disadvantages of this method are a low detection rate of affected pregnancies (no more than 15%) and iatrogenic miscarriages (0.5-1%). Pregnant women under the age of 36 are not eligible for screening, even though 70% of the children with Down's syndrome are born in this age group. Screening by measuring nuchal translucency thickness, an early ultrasound marker for Down's syndrome carried out in the first trimester of pregnancy, has a higher detection rate with a less invasive method and therefore fewer iatrogenic miscarriages. However, Dutch law prohibits the offer of screening to women with a low individual risk of DS (Population Screening Act), because of the anxiety this may provoke in these women. The Dutch Health Council's Prenatal Screening Committee has advised the minister of Public Health, Welfare and Sport that risk-assessment screening, in particular the triple test, should no longer be postponed and that research into (other) screening options should be stimulated.