Heart Disease in Pregnancy - The Risks
Pregnancy is one of the physiological conditions that places a considerable burden on the heart,
forcing it to work harder for a significantly long period - nine months. While a normal heart is quite
capable of taking this extra workload right in its stride, a diseased one may not be able to cope.
Different kinds of heart disease may cause different problems during pregnancy. In this series of
articles I plan to discuss this topic in depth.
Risk during pregnancy to the mother with heart disease
Pregnancy poses an inordinately high risk for mothers with heart disease in conditions where blood
flow into the lungs is obstructed. The block may be at the
- inlet to the lungs, the pulmonary valve e.g. pulmonary stenosis
- outlet from the lungs, the mitral valve e.g. mitral stenosis
In both of these situations, blood flow into the lungs does not keep pace with the increased flow to
the rest of the body imposed by the pregnant state.
The diseases which are associated with the highest risk to the mother during pregnancy are:
- Eisenmenger syndrome (severe pulmonary hypertension as a consequence of a long standing
left to right shunt lesion like ASD, VSD or PDA) in which the maternal mortality risk is as
high as 30-50%
- Primary pulmonary hypertension, a disease of unknown cause that increases the resistance to
blood flow in the lungs
- Cor pulmonale, a disease of lung blood vessels secondary to smoking or other lung fibrosing
- Pulmonary venous occlusive diseases which block the outflow of blood from the lungs back
to the heart
Among the congenital heart diseases, Tetralogy of Fallot carries a risk of 4 to 20% of mortality in
the mother. Atrial septal defects are perhaps the safest of all birth defects. Even with more the
serious conditions, obsessional care can reduce the risks considerably.
Rheumatic heart valve disease is another risk, with patients having mitral stenosis having a 1%
chance of developing pulmonary edema during pregnancy. Other diseases like Ehlers Danlos
syndrome (a disorder of the connective tissue of the body resulting in loose skin and lax joints) can
cause a higher risk of bleeding from major blood vessels that might rupture during pregnancy.
Risk to the fetus during pregnancy with heart disease
In mothers with rheumatic heart valve disease, the fetus develops almost normally. The only
difference noted is a mild growth retardation, with babies being lighter by around 200 grams.
In mothers with congenital heart disease too, pregnancy is almost normal in diseases without
cyanosis. However, in cyanotic mothers, many problems like severe growth retardation and higher
abortion rates arise. Because the maternal blood has a very low oxygen content, there is a lower
oxygen exchange across the placenta, and the fetus gets lesser oxygen than normal. As a result, the
fetus dies or is delivered prematurely. The situation is however reversed after surgical correction is
Coarctation of the aorta is another special condition, in which fetal loss is higher than normal (13%)
as a result of lower blood flow to the placenta due to the narrowed aorta.
Will the fetus also develop congenital heart disease ?
A question most parents who themselves have birth defects will ask their doctor is "Will my child
also have CHD ?" The risk of congenital heart disease in such pregnancies is 2-4 %, which is twice
the incidence of heart disease in the general population. This risk also varies with different
conditions. For instance, it is 3% in parents with Tetralogy of Fallot but almost 18% in those with
Another interesting fact is that such defects are concordant - that is, the defect in the child is usually
the same one as of the mother. Importantly, if the mother's defect was one caused by an external
factor - for example, by exposure to a drug, or an infection with German measles during gestation -
then the fetus of such a person would have a risk of birth defects SIMILAR to the general
In the next article, we will see how congenital heart disease affects the pregnancy.