Reply

We would like to thank Dr Vigneswaran and colleagues for their insightful Correspondence regarding our recent article on indications for fetal echocardiography (FE)1. We greatly appreciate their reflections, which highlight important points that complement and extend our work. Congenital heart disease (CHD) is one of the most common congenital anomalies, representing a major cause of perinatal morbidity and mortality. Prenatal diagnosis of selected types of CHD has been shown to improve fetal and neonatal outcomes2. Importantly, most cases of CHD occur in pregnancies without any recognized risk factors: the so-called ‘low-risk’ group. In this setting, a suspected cardiac abnormality at the routine anomaly scan remains the most specific indication for FE, with a lower false-positive rate than other referral criteria. This emphasizes the pivotal role of effective national screening programs in identifying fetuses who will benefit the most from detailed cardiac evaluation. The role of second-trimester screening in the detection of CHD has improved over time, owing to advances in ultrasound technology, the implementation of extended protocols and enhanced operator training3. Nevertheless, the effectiveness of screening is highly variable across countries, and CHD remains the most frequently missed congenital anomaly on prenatal ultrasound4, 5. Population-based studies demonstrate that, even in regions with long-established screening programs, such as France, a significant proportion of CHD continues to be diagnosed only postnatally6. These findings indicate persistent gaps in prenatal detection and the need for further refinement of screening practices. FE has evolved over several decades. In the 1980s, seminal studies of Allan et al. defined the normal fetal cardiac anatomy using real-time ultrasound and M-mode7, establishing that CHD could be diagnosed before birth8. Reference data on cardiac dimensions and valve motion were produced, and the introduction of Doppler imaging techniques in the late 1980s and 1990s allowed assessment of blood flow and hemodynamics9. More recently, three- and four-dimensional ultrasound imaging10, 11 combined with standardized protocols have expanded the diagnostic potential of FE, making it an indispensable component of modern prenatal medicine. We acknowledge the points raised regarding the so-called ‘intermediate’ FE, which is usually part of a tiered, detailed fetal anatomical examination12, and differs from the standard FE protocol13. While we understand the rationale for such an approach, it is not standardized and, when performed by experts in fetal medicine who are already trained and competent in FE14, it is debatable whether a partial evaluation offers any advantage over complete FE, which may further improve detection rates. Moreover, as our systematic review showed, there is insufficient evidence to categorize many maternal and fetal risk factors as low-, medium- or high-yield, underscoring the urgent need for new studies to refine these categories1. We agree with Vigneswaran et al. on the importance of developing structured curricula, defined training requirements and audit systems for FE. Nevertheless, even with optimal training, some types of CHD, such as isolated total anomalous pulmonary venous connection15, 16 and coarctation of the aorta17, remain challenging to detect prenatally. This highlights the limitations that may be inherent to the method, rather than the operator. An intermediate FE may be reasonable in the context of a comprehensive referral scan performed by a fetal medicine specialist for pregnancies with maternal or fetal anomalies that increase the likelihood of congenital malformations12, 18. In such settings, a detailed evaluation of the entire fetal anatomy, including advanced cardiac assessment, is already part of clinical care and may obviate the need for a separate, additional FE. Emerging evidence also supports risk stratification within specific maternal conditions. For instance, in pregestational diabetes mellitus, hemoglobin A1c (HbA1c) > 8.0% in the first trimester confers a 4-fold increased risk of major CHD compared with normal levels of HbA1c19. Similarly, the risk of CHD rises exponentially with increasing nuchal translucency (NT), with NT ≥ 3.5 mm (≥ 99th percentile) providing the highest sensitivity and specificity for prenatal CHD detection20. Such findings can help refine referral criteria and optimize the use of FE, particularly in resource-limited settings. In conclusion, indications for FE should be based on evidence-driven criteria, identifying those patients at the highest risk. The need to refer patients for FE will evolve as national screening programs improve, new evidence clarifies the impact of risk factors, training becomes more structured and technologies advance. Ultimately, it is key to achieve a balance between accessibility, standardization and evidence-based practice, to ensure that FE delivers maximal benefit for both patients and healthcare systems.