Cardiovascular contraindications to pregnancy

Cardiovascular contraindications to pregnancy

Abstract: In general, obstructive lesions and severe cyanotic lesions are poorly tolerated in pregnancy while regurgitant lesions and left to right shunts without pulmonary hypertension are well tolerated.

Pregnancy is associated with several hemodynamic changes. As term advances there is increase in heart rate and cardiac output while the peripheral resistance falls in pregnancy. Blood volume also increases in pregnancy and there is a sudden increase in blood volume after delivery when the placenta separates and pushes the blood from the maternal aspect back into circulation.

Some of the important cardiovascular contraindications to pregnancy are:

1. Severe pulmonary hypertension
2. Severe obstructive valvular lesions
3. Severe cyanotic congenital heart disease
4. Marfan syndrome with dilated aorta

In severe pulmonary hypertension, the demand for increase in cardiac output with pregnancy cannot be met and the individual may develop low cardiac output state and right heart failure.

Severe mitral stenosis in pregnancy has a high risk of development of pulmonary edema. Pulmonary edema can also occur soon after delivery at the time of placental separation due to the extra volume load from release of blood stored in the maternal aspect of the placenta. The increase in heart rate in pregnancy is also deleterious in mitral stenosis as the shortened diastole decreases the left atrial emptying and consequently increases the left atrial pressure.

Other severe obstructive valvular lesions are also poorly tolerated in pregnancy because the obstructions make the cardiac output rather fixed, preventing the progressive rise in cardiac output needed in pregnancy.

Cyanotic heart diseases with significant systemic desaturation are also poorly tolerated in pregnancy. In Eisenmenger syndrome there is dual risk of pulmonary vascular obstruction limiting the rise in cardiac output and the systemic desaturation due to the right to left shunt.

Marfan syndrome with dilated aorta is prone for aortic dissection and rupture during pregnancy as the hormonal changes in pregnancy is likely to worsen the weakness of the aortic connective tissue. Risk of rupture is highest during parturition due to the increased intrathoracic pressure while straining for labour.