Forced squatting is a squatting position or knee-to-chest position to relieve symptoms due to difficulty in breathing and palpitations during short distance walking or other activities. It is the main symptom of cyanotic congenital heart disease. So what are the causes of this disease? 1, factors of fetal development environment Viral infection in utero is one of the most important causes of congenital heart disease, among which rubella virus infection is the most prominent. If a mother suffers from rubella in the first trimester of pregnancy, she will have a higher rate of congenital heart disease in her baby. Other conditions such as amniotic membrane lesions, fetal compression, early preterm abortion, diabetes mellitus, phenylketonuria, and the use of radiation and cytotoxic drugs in early pregnancy can also cause congenital heart disease in the fetus. The mother took certain drugs during pregnancy, which can also lead to fetal heart malformation. 2, premature birth Premature birth may also lead to congenital heart disease, this is because the ventricular septum of premature babies before birth has not completed development, prone to ventricular defects. And newborns born with a weight of less than 2500g do not have a strong vasoconstriction response and are more likely to suffer from congenital heart disease. 3, plateau environment The prevalence of this disease in China’s Qinghai plateau is much higher than that in the plains because of the low partial pressure of oxygen in the plateau. There are more congenital heart disease, ductus arteriosus and congenital heart disease atrial defect in plateau area. 4, genetic factors Genetic factors are the most common cause of congenital heart disease. If someone in the family suffers from congenital heart disease, it can be considered to be due to genetic factors. Genetic studies have concluded that most congenital heart disease is formed by the interaction of multiple genes and environmental factors.