Pregnancy is considered to be high-risk for individuals with cyanotic heart diseases such as Tetralogy of Fallot and is not recommended for individuals with severe untreated forms. There may be a danger of the formation of blood clots, causing strokes in extreme cases, as a woman's blood coagulates more easily during pregnancy. Other changes in circulation may increase right to left shunting, which reduces even further the oxygen supply to the body tissues. This may lead to further complications that pose risks to both mother and child.
Accordingly, the untreated Tetralogy of Fallot patient should not undergo pregnancy, especially if oxygen saturations are below 85%. There is a 30% fetal mortality rate for un-operated Tetralogy of Fallot patients, and maternal mortality may be as high as 15%. However, the woman who receives an effective repair operation prior to pregnancy can expect a good chance of success. If the hemodynamics (blood pressures and saturation of oxygen and other gases) are near normal, then the level of risk will approach that of women with normal hearts.
Careful monitoring by health professionals is imperative during pregnancy. In some cases the increased blood volume may cause heart failure or the development of arrhythmias. Other potential difficulties include pulmonary valve regurgitation, right ventricular dysfunction, and right ventricular outflow tract obstruction. In some cases, minimal activity and bed rest may be recommended, and treatment with anticoagulants and oxygen therapy may be prescribed. Echocardiography is often used to monitor fetal development and Cesarean section may be selected as the safest form of delivery.
Anyone with congenital heart disease, repaired or non-repaired, should consult with their cardiologist prior to becoming pregnant to review the risks.