First Trimester Screening (FTS)

First Trimester Screening (FTS)

First Trimester Screening (FTS) is a non-invasive method of assessing early fetal growth, anatomy, and the chances of certain chromosomal differences. It is performed through ultrasound and bloodwork at 11-14 weeks gestation.

PCRM is excited to announce that, as of 2020, our FTS program also includes screening for pre-eclampsia (PE), a multi-system disorder that affects 2-5% of pregnant women and is a leading cause of maternal and fetal morbidity and mortality. It is characterized by high blood pressure and signs of damage to organ systems, usually the liver and kidneys. PE screening details are provided below.

First Trimester Screening, Explained

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 that 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).

The most common chromosome differences 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:

• Nuchal Translucency (NT) – a fluid-filled space located behind an infant’s neck
• Blood work for PAPP-A and free-beta HCG (proteins in the mother’s blood)
• Nasal Bone (NB), which helps doctors to determine the probability of chromosomal abnormalities, such as Down’s syndrome
• Fetal Heart Rate (FHR)
• Ductus Venosus Flow (DV), which plays a vital role in ensuring proper circulation during fetal development

The combination of all six, in conjunction with maternal age, provides a 96% likelihood of detection, with a 3% chance of a falsely positive result. Full fetal anatomy is also reviewed for major defects.

PE Screening, Explained

PE screening uses a combination of maternal risk factors, blood pressure measurements, ultrasound, and blood test markers to predict the risk of pre-term PE in a pregnancy. Women identified at high risk for PE are recommended to take prophylactic aspirin to reduce their risks. PE screening includes:

• Mean Arterial Pressure (MAP) – the mother’s blood pressure
• Placental Growth Factor (PGF) – protein in mother’s blood
• Pregnancy-associated plasma protein A (PAPP-A) – protein in mother’s blood
• Uterine Artery Pulsatility Index (UTPI), if applicable
• Additional Pregnancy Screening Options

PCRM offers several options for prenatal screening, including first-trimester screening (FTS), non-invasive prenatal testing (NIPT), pre-eclampsia screening (PE), and a combination of the three (TriO). The following table summarizes what each prenatal screening option offers.