Abstract Background: To examine the correlation between maternal environmental tobacco smoking during pregnancy as well as the risk of congenital heart defects (CHDs) incidence in offspring. Aim of Study: To examine the correlation between maternal environmental tobacco smoking throughout pregnancy and the CHD incidence risk in offspring. Patients and Methods: This is a case-control study that was conducted on two groups of patients presented to the Pediatric Cardiology Unit, Ain Shams University Hospitals, including group 1: 120 mother of live born infant diagnosed with congenital heart disease confirmed by echocardiography done by a specialized echocardiologist, And group 2: 120 mother of infant with normal heart, using questionnaire. Work start at May 2020 and end in May 2021. Results: There was a statistically significant increase in the incidence ofCHDs among children whose mothers have been exposed to smoking during pregnancy than those with no history of exposure (p-value=0.003). There was also a substantially elevated risk of CHD with respect to time of exposure during pregnancy (p-value=0.001). Additionally, There was a statistically significant increase in CHDs incidence among children whose mothers had a history of the first trimester and preconception smoking exposure. ETS (ENVI-RONMENTAL TOBACCO SMOKE) >15 minper day (p-value=0.007 being more ingroup of mothers with children with CHDs. Conclusions: Maternal exposure to smoking substantially impacts the increased incidence of CHDs in general. This study observed that maternal ETS >15 minutes per day (passive smoking) is associated with increased CHDs.