The study aimed to identify risk factors and assess their contribution to the formation of congenital heart defects in newborns. 374 newborn children were examined, who were divided into groups II: Group I consisted of 324 newborns with congenital heart disease, group II consisted of 50 newborns without congenital heart disease. To determine the significance of risk factors, a questionnaire was compiled with a codifier of 42 signs reflecting socio-hygienic, medical and biological factors, the presence of intrauterine infections and the mother’s medication intake during pregnancy and obstetric and gynaecological history. The questionnaire was filled out by the mothers of the examined newborns. The studies were conducted using: an epidemiological study of risk factors, an analysis of information content on relative risk – RR and the calculation of the odds ratio – OR. The results of the studies showed that the modifying risk factors for the development of congenital heart defects (CHD) in newborns are: the age of the mother over 35 years (OR 2.57), closely related (OR 4.69) and unregistered marriage (OR 4.48), the presence of CHD in the family (OR 7.70), severe anaemia (OR 3.65), acute upper respiratory tract infections during pregnancy (OR 3.98), herpetic viral infection (OR 48.8), taking antifungal drugs (OR 3.24), the presence of miscarriages (OR 8,11), the threat of termination (OR 5,12) and induced pregnancy (OR 5,68), severe toxicosis (OR 3,49), fetal hypoxia (OR 4.01) and stress during pregnancy (OR 7.50). Thus, when assessing the risk of developing congenital heart defects in newborns, the use of the modifying factors identified by us will allow planning methods of prevention in families at high risk of the disease.