Congenital heart defects (CHD), as the leading cause of birth defects, affect 12 million people globally and approximately 41,000 newborns each year in Europe. CHD presents a significant public health concern due to its association with high morbidity and mortality rates across the lifespan. Over 50% of infants born with critical CHD will develop neurodevelopmental disorders (NDD), requiring specialized care and impacting their quality of life. NDDs, involving early and persistent disruptions in cognitive, emotional, and behavioral development due to abnormal brain development, are highly variable. They may impact language, learning, motor skills, intellectual efficiency, social cognition, attention, memory, and executive functions, often accompanied by psychosocial difficulties. These hidden disabilities constitute the primary long-term sequelae of CHD, surpassing even cardiovascular complications in impact, and affect children who often undergo multiple cardiac surgeries during early childhood. NDDs are associated not only with complex CHDs but also with simpler CHDs that are repaired in early childhood and considered 'cured.'

The origin of CHD-associated NDDs remains largely unknown. While few genetic or environmental causes have been identified, recent research suggests a possible common origin linking heart malformations and neurodevelopmental abnormalities. The CATAMARAN neonatal cohort project aims to detect developmental delays associated with CHD as early as six months of age and to identify both individual susceptibility factors and acquired vulnerabilities contributing to the development of NDDs in infants with CHD.

The inclusion criteria are as follows:

• Fetus with a congenital heart defect (CHD) detected prenatally (prenatal diagnosis of the heart defect)
• Fetus with a critical CHD defined as requiring cardiac surgery during the first three months of the infant's life
• Parents affiliated with or beneficiaries of a social security or equivalent system
• Parents' good understanding of the French language
• Voluntary, informed, and written consent from both parents for themselves and the unborn child

Criteria for parents*:

- Biological parents *The inclusion of the father in the project does not limit the participation of the child (patient) in the study.

*The father will be encouraged to participate in the project by providing a blood sample to create a trio (mother/father/infant) for future genetic analyses.

However, if the father is unavailable or does not consent to the collection and storage of samples for analysis (as part of the CATAMARAN study or future research projects related to biobanking), the child can still be included in the study.

Exclusion Criteria:

• Medical termination of pregnancy considered
• Genetic anomaly or malformative syndrome identified prior to inclusion

The study population will focus on the inclusion of 150 fetuses with a prenatally diagnosed critical congenital heart defect (CHD), at high risk of developing developmental delays, and their two parents.