Can a detailed nuchal translucency (NT) scan detect enlarged ventricles and heart defects?

Detecting Enlarged Ventricles and Heart Defects During NT Scan

Yes, a detailed nuchal translucency (NT) scan can detect enlarged ventricles and heart defects, though with varying sensitivity depending on gestational age and the expertise of the center performing the scan. 1

Detection of Heart Defects During NT Scan

Capabilities of NT Scan for Heart Defect Detection:

• First trimester fetal echocardiography performed at 11-14 weeks can identify 50-65% of major heart anomalies in low and high-risk patients respectively 1
• At a nuchal translucency threshold of ≥3 mm (99th percentile), approximately 1% of patients will require standard second trimester fetal echocardiography 1
• Early cardiac evaluation is possible at 13-14 weeks in over 90% of cases 1

Types of Heart Defects Detectable:

• Approximately half of hypoplastic left heart and atrioventricular septal defects can be detected at 11-14 weeks 1
• Less than a quarter of conotruncal abnormalities are detectable at this early stage 1
• The risk of congenital heart disease is 6.6 times higher in fetuses with increased NT compared to those with normal NT 2

Limitations and Follow-up:

• Detection rates vary according to the experience of the center, population studied, and type of defect present 1
• First trimester pitfalls can result in both false-positive and missed diagnoses 1
• A repeat fetal echocardiogram is still recommended in the second trimester (18-22 weeks) for pregnancies with increased nuchal translucency 1

Detection of Enlarged Ventricles (Brain Abnormalities)

Capabilities for Brain Abnormality Detection:

• The NT scan can provide an opportunity to screen for structural fetal anomalies when viewing within the sagittal planes of the fetus 3
• Brain abnormalities such as acrania, holoprosencephaly, Dandy-Walker syndrome, and cerebellar agenesis can be detected during NT examination 3
• Early fetal anatomic survey may be performed at the time an increased NT is identified, providing opportunity for early detection of major malformations affecting the brain 1

Limitations for Brain Abnormality Detection:

• The sensitivity of ultrasound at 11-14 weeks for detection of congenital anomalies is only about 50% compared to 75% at 18-22 weeks 1
• Detailed assessment of brain structures is more challenging in the first trimester due to ongoing fetal development

Recommendations for Optimal Detection

When Increased NT is Detected:

• When NT measures ≥3 mm, genetic counseling and diagnostic testing should be promptly offered 1
• An early fetal anatomic survey should be performed to detect major malformations affecting the brain, heart, abdominal wall, and limbs 1
• A detailed second trimester anatomic survey and fetal echocardiogram should be performed regardless of genetic testing results 1

Improving Detection Rates:

• Addition of simple cardiac scan to the combined first trimester screening parameters improves detection of major congenital heart defects 4
• Assessment of ductus venosus blood flow and tricuspid regurgitation can enhance detection of heart defects 4
• In experienced centers, early fetal echocardiography has a high degree of accuracy 5

The detection of enlarged ventricles and heart defects during NT scan is possible but should be confirmed with follow-up detailed anatomy scan at 18-22 weeks for comprehensive assessment, as this remains the gold standard for structural anomaly detection.