Objectives: This study aims to explore the clinical value of prenatal ultrasonography in the diagnosis of the common arterial trunk (CAT) classification and associated deformities. Materials and methods: The two-dimensional ultrasound images spatiotemporal image correlations (STICs) and clinical data of 108 foetuses diagnosed with CAT malformations were retrospectively analysed, their CAT types were classified, and the correlations between these different types and foetal malformations and pregnancy outcomes were analysed. Results: Among the 108 foetuses, there were 47 cases (43.5%) of type A1, 51 cases (47.3%) of type A2, 9 cases (8.3%) of type A3 and 1 case of type A4 (0.9%), of which 22 cases (20.4%) were isolated CAT, 56 cases (51.8%) had complex intra-cardiac structural abnormalities, 30 cases (27.8%) had intra-cardiac or extra-cardiac structural abnormalities, 17 cases had 1 other system abnormality, and 5 cases had 2 other system abnormalities. Four cases were combined with 3 other system abnormalities, while 4 cases were combined with 4 other system abnormalities, among which the facial and physical abnormalities had the highest incidence (40.0%). The STIC images were completely displayed in 88 cases (81.5%). Isolated CAT and CAT combined with other malformations were significantly correlated with foetal pregnancy outcomes ( P < 0.05). Conclusions: Prenatal ultrasonography had a high clinical application value for classifying CAT. Pregnancy outcomes were highly correlated with the classification and combined intra-cardiac and extra-cardiac structural malformations. The early assessment of foetal prognosis before birth has great value for clinical intervention.