Hypoplastic left heart syndrome identified or displaying anomalies during the first trimester of pregnancy: case reports

Hypoplastic left heart syndrome (HLHS) represents the most prevalent form of functional single-ventricle heart disease developing in utero. Enhanced ultrasound technology, featuring a spectrum of high-frequency probes, coupled with the diagnostic “window” at the 11–14 weeks’ scan, facilitates the early detection of HLHS during the first trimester of pregnancy. This not only permits timely genetic testing and management planning but, crucially, might uncover early indicators of hemodynamic alterations in HLHS. It is in this context that we described two different evolution of HLHS in utero. We present three instances of fetal HLHS identified or displaying anomalies in the first trimester: two exhibited the typical clinical phenotype early on, while the other manifested an outflow tract obstruction that evolved into HLHS by the second trimester. Insights into the HLHS spectrum may bridge the knowledge gap regarding the etiology of HLHS, which is essential for providing antenatal counseling, and guiding intrauterine therapy for the affected fetus.