Challenges in prenatal screening and diagnosis in the Netherlands

The Dutch prenatal screenings program consists of the combined test (CT) and the 20 week anomaly scan. All pregnant women are informed about prenatal screening, however the uptake of the CT is low, especially among younger women.
The CT is based on the measurement of the nuchal translucency (NT), maternal age and serum markers and has a detection rate around 90% for a false positive rate of 5% for trisomy 21, 18 and 13. Measurement of the NT is performed by certified sonographers, but still remains difficult to perform. Semi-automated measurement methods were developed to help assist, however well-trained operators do not seem to benefit from the use of them.
Once an increased risk or increased NT is found, women are counseled on the possibility of prenatal diagnostics. When performed by experienced operators the pregnancy losses associated with prenatal diagnostics are lower than previously reported.
However, an increased NT is much more than just a marker for trisomy 21, 18 or 13. There is a long and still growing list of genetic syndromes associated with it, and the most frequently reported is Noonan syndrome (NS). When specific prenatal ultrasound findings for NS are present, targeted DNA-analysis is indicated.
It may well be that the first trimester assessment will lose its character of primarily screening for chromosomal anomalies and become the first and most important moment of a general risk assessment in pregnancy. This new role of the first trimester assessment may revolutionize the model of care.