Background <p>To investigate the clinical value of fetal heart quantification (fetal HQ) in the evaluation of right ventricular size, morphology and cardiac function in fetuses with redundancy foramen ovale flap (RFOF).</p> Methods <p>31 fetuses diagnosed with RFOF through echocardiography from September 2021 to December 2023 were selected as the control group, and 62 healthy fetuses that matched the age and gestational period of the pregnant women in the RFOF group were chosen as the control group. Fetal HQ software provided by GE Voluson E10 was employed to automatically track endocardial parameters of the right ventricle in 24 segments.</p> Results <p>The internal diameter of foramen ovale in RFOF group was significantly smaller than that of normal fetal diameter in control group, with statistical significance (<i>P</i> &lt; 0.05). Comparing the morphological parameters of the fetuses in the RFOF group and the control group, there was no statistically significant difference in the GSI scores (<i>P</i> &gt; 0.05), but the RV-LED of the fetuses in the RFOF group in the segments of 1–24 were higher than the fetuses in the normal control group (both <i>P</i> &lt; 0.05), and the RV-SI was lower than that in the normal control group (all <i>P</i> &lt; 0.05).</p> Conclusions <p>The Fetal HQ technique enables accurate localisation of the site of the RFOF foetal lesion by rapid quantitative analysis of morphological and functional parameters of the right ventricle of the foetal heart.</p>