Heart development occurs primarily during the first 6-10 weeks of pregnancy. Therefore, by the time a woman learns she is pregnant, her baby's heart is largely formed. Exposure to any adverse factors during the first 10 weeks of gestation can contribute to the development of congenital heart disease. In a genetically predisposed baby, exposure to infection, radiation, electromagnetic fields, medication, or other harmful substances (alcohol, drugs, polluted air, etc.) during this period, as well as maternal malnutrition, are risk factors that can lead to congenital heart defects such as tetralogy of Fallot. However, complete evidence-based information on this is lacking. The etiology of the disease is multifactorial, meaning it results from a combination of several factors.