This article explores first-trimester anomaly screening and the potential for early detection of fetal abnormalities.
Traditionally, clinicians have used first-trimester ultrasounds for confirming fetal viability, pregnancy dating, detecting multiple pregnancies, and measuring nuchal translucency as part of the combined or sequential first-trimester screening protocol for aneuploidy. But is it feasible and reliable to introduce the detection of fetal abnormalities in the first trimester?
Advancements in ultrasound technology, especially improvements made by equipment providers, have paved the way for more detailed imaging. This innovation makes early anomaly screening possible, allowing clinicians to provide critical information to parents at an earlier gestational age than what is common today.
Professor Papageorghio & Professor Meagher's full video can be seen HERE.
Current Practices of First-Trimester Anomaly Screening
Dr. Aris Papageorghiou, Professor of Fetal Medicine at the Oxford Maternal and Perinatal Health Institute, discusses the current practices of first-trimester anomaly screening, citing UK data. Despite the lack of official guidance in many regions, a significant number of hospitals already engage in some form of anomaly screening. These screenings are driven by skilled sonographers and go beyond simply confirming fetal viability. However, there is substantial variation in anomaly screenings across different regions and hospitals, leading to an inequity of care. The healthcare industry must address this variation and its potential impact on patient outcomes.
To better understand the implications of screening variation, Dr. Papageorghiou delves into a comprehensive analysis of one million pregnancies screened over a two-year period. The data reveals a strong association between the use of a screening protocol and the detection of abnormalities. Notably, hospitals with established protocols demonstrate higher detection rates for various abnormalities, underlining the significance of a structured approach.
First-trimester ultrasound has proven to be effective for the early detection of numerous fetal anomalies, including conditions such as:
- Encephalocele
- Cleft lips and palates
- Spina bifida
- Limb reduction disorders
- Tetralogy of Fallot
- Hypoplastic left heart syndrome
- Atrioventricular septal defects
A structured approach and protocol during a first-trimester ultrasound anomaly screening has been shown to improve detection rates for these and other conditions. Earlier diagnosis of these conditions provides extra opportunities for testing, education, and, in some cases, earlier and safer termination.
Applications for Fetal Cardiac Abnormalities
Building on this data, Dr. Papageorghiou emphasizes the importance of these structured protocols in first-trimester anomaly screening.
Through a meta-regression analysis, he demonstrates that protocols significantly enhance detection rates, particularly for cardiac abnormalities. He draws attention to the incremental improvement in detection rates based on the complexity of the protocol, reinforcing the idea that a structured approach is paramount. Specifically, only 13% of cardiac abnormalities are detected with an unstructured approach. However, with modern techniques and ultrasound equipment, a structured approach can detect up to 78% of cardiac abnormalities in the first trimester.
Parents and Early Anatomic Screening Decisions
The video shifts the focus to the parents' perspective by discussing a national study on the acceptability of early anatomical screening. The study involves two cohorts: one comprising all parents and the other specifically including those with previous abnormal screenings.
Surprisingly, the acceptance rates for first-trimester screening are high, with 91% of parents expressing a desire for anatomical assessment at 11 to 14 weeks. This finding challenges the notion that patients prefer protection from false positives and underscores the importance of providing information and choices to expectant parents.
Demonstrating How a First-Trimester Anomaly Scan Would Work
Next, Professor Simon Meagher, a consultant sonologist and an internationally renowned expert on obstetric ultrasound from Australia, gives a practical demonstration of a first-trimester anomaly scan. The speaker emphasizes key techniques and uses a recorded ultrasound to demonstrate a detailed and unedited examination of a first-trimester fetus.
This exam starts with the anterior horns and falx cerebri, nuchal translucency, nasal bone, maxilla, lateral ventricles, brain stem, intracranial translucency, and cisterna magna. Next, Dr. Meagher demonstrates the aqueduct of Sylvius and the thalami and the correct techniques for measuring the biparietal diameter and head circumference, femur length, and abdominal circumference. He also visualizes the stomach and cord insertion.
Early diagnosis plays a pivotal role in the evolving landscape of genomics and prenatal screening. Dr. Meagher advocates for managing pregnancies with malformations through timely interventions, utilizing chromosomal microarray or chorionic villus sampling. The discussion underscores the practical aspects of scanning, emphasizes the necessity of a detailed examination of organs like the brain and heart, and focuses on the time spent on each organ.
Cardiac Abnormalities
Dr. Meagher shows a visualization of the heart's anatomy, including a four-chamber view color demonstration of the outflow tracts. He also explains how to determine the situs and axis of the heart. He spotlights various detectable cardiac anomalies and the ultrasound signs to look for during the examination.
As part of this examination, he demonstrates the diagnostic value of SlowFlowHD, a modern ultrasound tool on the GE HealthCare Voluson™ platform. This tool allows clinicians to diagnose cardiac abnormalities in the first trimester and visualize tiny vessels and branches in and around the heart, such as the pulmonary veins and the three-vessel tracheal view. Dr. Meagher calls attention to specific cardiac abnormalities, including tetralogy of Fallot, coarctation, and transposition of the great arteries.
Brain Abnormalities
Additional details of the brain anatomy are offered with four views of the intracranial anatomy. Dr. Meager gives a detailed explanation of different ultrasound settings that provide improved views of intracranial features. The exam progresses to skeletal and limb features, the intra-abdominal organs, and the major vessels, again with enhanced views using SlowFlowHD technology.
Musculoskeletal Abnormalities
Dr. Meagher uses different ultrasound settings to provide more views of the mandible and maxilla to detect clefts and micrognathia, plus spinal segments and the remaining skeletal features. He highlights challenges when examining the spine, particularly in 10 to 15% of cases where a complete view may be elusive. This entire examination takes less than 20 minutes. Dr. Meagher discusses the role of this first-trimester anomaly examination in modern genetic and cell-free DNA screening and integration with later anatomic ultrasounds.
The Potential for First-Trimester Abnormality Screening with Technological Advances
Overall, this video provides valuable insights for obstetricians seeking to refine their ultrasound practices and navigate the complexities of early pregnancy assessments. It also emphasizes the exciting promise of new ultrasound technology, which has revolutionized imaging quality with incredible clarity and detail and vascular image acquisition with SlowFlowHD technology. This advancement allows clinicians to move from merely confirming fetal viability to performing detailed anomaly screenings in the first trimester of pregnancy.
