First Trimester Screening – Double Marker Test (11 to 13+6 weeks)

The parents and the doctors indeed want to know as early as possible about the possibility of genetic anomalies. The earliest window available for getting such information is between 10 to 14 weeks (or 13 weeks + 6 days to be more precise) through the double market test and NT scan.

The NT Scan or Ultrasound Scan

The ‘NT Scan’ as it is popularly known as is an ultrasound scan performed in the first trimester (between 11 to 14 weeks) to measure Nucal Translucency (NT) and nasal bone (NB). This gives important information about the babies’ health and progress of the pregnancy. The ultrasound scan should be combined with the biochemical marker to arrive at a more definitive risk assessment.

Double Marker – Two Biochemical Parameters

It has been found that there is a strong correlation between certain biochemical parameters and the fetal abnormalities. Two such biochemical parameters which are relevant in the first trimester are Free Beta-human chorionic gonadotropin (Free B-HCG) and ‘Pregnancy-Associated Plasma Protein (PAAP-A). By combining the result of the NT Scan and the two biochemical parameters (Dual Maker or Double Marker) into a sophisticated risk calculation algorithm or software, we can provide a reliable indication for the risks of Down Syndrome (Trisomy 21), Edwards Syndrome (Trisomy 18) and Patau Syndromes (Trisomy 13). The First Trimester Screening presents significant advantages over other tests because of higher detection rates (90-95% with 5% false positive rates), and the availability of information at an early stage of pregnancy. ~ (Reference: Fetal Medicine Foundation)