Introduction: Filling a Gap in Fetal Cardiac Reference Ranges
Understanding normal growth patterns of fetal cardiovascular structures is essential for early detection of subtle cardiac abnormalities. This study, conducted in the north-eastern Egyptian population (Qalyubiyya Governorate), provides gestational age–specific reference ranges and nomograms for a comprehensive set of fetal cardiac dimensions from 14+6 to 36+6 weeks. By leveraging a large, well-defined cohort of low-risk, singleton pregnancies, the work offers crucial baseline data to improve prenatal care and outcomes.
What Was Measured and How
In a cross-sectional design, 900 healthy pregnant women underwent routine antenatal scanning with standardized two‑dimensional echocardiography. Measurements encompassed a broad spectrum of cardiac structures and thoracic parameters, including:
- Cardiac circumference (CC) and thoracic circumference (TC)
- Inner diameters of the right and left atria and ventricles
- Foramen ovale diameter, myocardial wall thickness, and interventricular septal thickness
- Diameter of atrioventricular valve rings, aortic and pulmonary annuli, and great vessels
- Transverse diameter of the ductus arteriosus and three-vessel views
- Cardiac axis, and cardiothoracic ratio (CTR)
All measurements adhered to ISUOG and American Society of Echocardiography guidelines, with image quality playing a critical role in ensuring reliable data. Gestational age was determined by a combination of last menstrual period data and early fetal measurements (femur length, biparietal diameter, abdominal circumference).
Key Findings: Growth, Models, and Nomograms
Across the 14+6 to 36+6 week window, all fetal cardiac dimensions increased with gestational age. Distribution of measurements was non‑normal, and multiple regression models (linear, cubic, quadratic, exponential) were evaluated. The quadratic model consistently provided the best fit for most cardiac dimensions, yielding robust equations to estimate each measurement from gestational age. Centile curves (10th, 25th, 50th, 75th, 90th) were generated, along with comprehensive nomograms, to translate gestational age into expected cardiac dimensions.
The study also examined relationships between major structures through ratios such as RA/LA, RV/LV, PA/AO, and FO/AO root diameter. These ratios remained relatively stable or showed predictable small fluctuations, reflecting harmonious fetal heart development. For example, the RA/LA ratio hovered around 1.0–1.1, while the RV/LV ratio gradually approached 1.1 as gestation progressed. Such stability in proportional growth is valuable for identifying disproportionate remodeling early in pregnancy.
Reference ranges were developed for 23 cardiac measurements, enabling clinicians to compare an individual fetus against population-based norms. The cardiothoracic ratio (CTR) and the difference between cardiac and thoracic growth were also characterized, supporting assessment of the heart within the evolving thoracic cage.
Clinical Relevance and Future Implications
This study marks the first attempt to construct government-level nomograms for fetal cardiac dimensions in a northeastern Egyptian population. The reference data provide a baseline for detecting deviations that may signal congenital heart disease or adverse fetal remodeling. Clinicians can apply these nomograms to refine prenatal risk stratification, tailor follow-up plans, and inform parental counseling in a regional context.
Future work could probe the applicability of these nomograms in other Egyptian subpopulations and explore longitudinal follow-up to correlate prenatal measurements with neonatal outcomes. Additionally, integrating these references into ultrasound software could streamline real-time interpretation during routine scans.
Limitations and Considerations
As a cross-sectional, low-risk cohort study, the findings reflect healthy pregnancies and may not capture the full spectrum of congenital anomalies. Nevertheless, the large sample size and standardized methodology strengthen the reliability of the derived nomograms for the target population.
Conclusion: A Foundational Resource for Fetal Cardiac Care in Egypt
The study delivers GA-specific reference ranges, regression equations, centile graphs, and nomograms for 23 fetal echocardiographic measurements in 900 low-risk singleton pregnancies. By enabling precise, early assessment of fetal cardiac remodeling, these nomograms contribute to improved prenatal care and outcomes in north-eastern Egypt and offer a model for similar regional investigations.
