First Trimester Screening (FTS) is a non-invasive method of identifying any risks of certain chromosomal abnormalities. We strive to help couples fully understand the options involved in this procedure. There are two versions of early genetic screening – one based on cell free fetal DNA, and the other on ultrasound and serum proteins. Both can now be integrated in the testing called DuO.
First Trimester Screening was developed largely through the work of the Fetal Medicine Centre, London, UK and the pioneering ideas of Professor Kypros Nicolaides. Since 1990, Nicolaides has been targeting research towards the early detection of genetic syndromes, in methods which involve examining the baby at an early stage in its development (the end of the first trimester, or 11-14 weeks). Since its inception, new discoveries have been added to the original finding of Nuchal Translucency (NT), and now provide the highest detection rates of any genetic screening tool.
The most common chromosome problems include trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), and trisomy 13 (Patau syndrome). All of these disorders affect the baby’s development and range in severity from mild to severe. In the process of FTS, 6 markers are used to statistically assess the chance of one of the syndromes. These markers all fall under a quality review program through the Fetal Medicine Foundation, to ensure reproducibility, and global uniformity of testing. The markers include:
NT – Nuchal Translucency
Blood work for PAPP-A and free-beta HCG (proteins in the mother’s blood)
NB – Nasal Bone
FHR – Fetal Heart Rate
DV – Ductus Venosus Flow
The combination of all six provides a 96% likelihood of detection, with a 3% risk of a falsely positive result. Full fetal anatomy is also reviewed for major defects.