Congenital heart defects (CHD) are a common cause of fetal death and termination of pregnancy for fetal anomaly (TPFA). No series with sufficient cohort, based on description of the anatomic phenotype of CHD discovered in fetal period, have been published until now.

The aim of our study is to phenotype all the fetal cardiac specimens of the M3C collection, which counts more than one thousand hearts.

A complete morphological examination of each specimen according to segmental analysis was performed by two observers (MH, LH). We determined the main CHD according to the 11 categories and 23 sub-categories of the clinical and anatomical classification of CHD and we coded the associated lesions with IPCCC codes according to the ICD-11 CHD classification. These codes were recorded in a database created for that purpose including photographs of each heart.

To date, we have analyzed 697 cardiac specimens. Among them, 64 were normal hearts (9%). The most frequent main groups of CHD were: anomalies of the ventricular outflow tracts (VOT) (197, 28%), functionally univentricular hearts (FUV) (164, 24%), anomalies of atrioventricular junction and valves (AVJV) (95, 14%).

The most frequent associated lesions were: anomalies of the valves (all valve type; 442, 63%), ventricular septal defects (241, 35%), interatrial communications (198, 28%), ventricular hypoplasia (172, 25%), anomalies of the arterial duct (152, 22%).

These first results confirm the predominance of the anomalies of the VOT. The high rate of FUV and anomalies of AVJV underlines the selection bias related to the high number of TPFA for severe CHD or chromosomal abnormality. This anatomical phenotyping of the collection should allow us to identify rare associations of malformations and could change our current way of grouping some phenotypes together. This could help us, by integrating current embryological knowledge, to elaborate a cladistic analysis of CHD.