Most parents who have had a child with major congenital heart disease become very scared and anxious when considering having another child. This is a totally understandable reaction. Parents are particularly anxious about the risks of their new baby having congenital heart disease. But what is the risk and can heart problems be detected earlier?
The risk of having another child with congenital heart disease:
Congenital heart disease affects up to 8 of 100 newborns making heart defects the most common malformation that children are born with; the risk in the normal population is 0.8%. The defects are comprised of all sorts of differences ranging from insignificant defects to complex forms such as single ventricle conditions. If you have one child or pregnancy affected with congenital heart disease there is an increased risk of your new baby having congenital heart disease. In general, considering all forms of congenital cardiac problems, the risk of having another child at least doubles to about 2-3% (2-3 of 100). Even if baby is a half sibling there is an increased risk, but this is less, about 1.2% (just over 1 of 100). This means the over-whelming likelihood is that, despite this increased risk, your next baby will not have congenital heart disease.
If you are one of these rare people to have another child with congenital heart disease, the type of heart problem is not necessarily the same as your previous child. However, some specific heart problems e.g. Tetralogy of Fallot, can run in families.
For parents who have a baby with Hypoplastic Left Heart Syndrome, future children are more likely to have heart problems where the left side of the heart is involved but not necessarily have Hypoplastic Left Heart Syndrome. These other heart problems include coarctation of the aorta and aortic stenosis. These do require intervention but often a two-ventricle (pumping chamber) circulation is possible. When there is recurrence of congenital heart disease in a family previously affected with Hypoplastic Left Heart Syndrome, about one third of the new babies will have Hypoplastic Left Heart Syndrome like their sibling.
For single ventricle heart problems the risk of having another child with a single ventricle heart does vary according to several factors:
- The type of congenital cardiac condition: There are many different types of functionally univentricular circulation and risk of recurrence depends upon the exact diagnosis of your previous child. For example, in classical Hypoplastic Left Heart Syndrome the risk of having another child with Hypoplastic Left Heart Syndrome has been reported to be as high as 8% (8 in 100) although this has not been my personal experience and I have found the recurrence much less. Some babies born with a functionally univentricular heart have ‘heterotaxy’ otherwise known as ‘left atrial isomerism’ or ‘right atrial isomerism’. These heart lesions are more likely to re-occur with the risk being as high as 25% or above (1 in 4). Families where parents are related are particularly at risk of having children with heterotaxy and these groups are also vulnerable to recurrence.
- Whether parents are related e.g. cousins. If parents are related there is an increased risk of recurrence.
- Whether a genetic cause has been found. Genetic tests are improving all the time and what can be tested is constantly changing. This is a fast-moving field and beyond the scope of this article. There is much ongoing research in identifying genetic causes for congenital heart disease. New techniques, such as whole genome sequencing, may be useful in the future however currently few types of congenital heart disease have an identifiable causative gene and therefore early ultrasound (see below) is the most practical way of finding out whether your new baby may have congenital heart disease. Referral to a clinical geneticist can be helpful particularly if there is recurrence of congenital heart disease in your family, if a causative gene has been found in your previous child with congenital heart disease, or if the heart anomaly was part of several structural anomalies. If this is the case, you should ask for a referral before you start trying for another child.
How early can a heart problem in my new baby be detected?
The best time to assess the fetal heart is 18-21 weeks gestation, however this is really quite far into pregnancy (4-5 months) and most parents who have already had a child affected with congenital heart disease want to know sooner if their new baby is also affected.
As technology has changed, the ultrasound equipment used for assessing babies in the womb has improved and we can now get some idea of whether baby is at risk of congenital heart disease in the first trimester by assessing the nuchal translucency (NT) and other features. The nuchal translucency is measured at your first fetal anomaly scan but the other specialist tests are available in some fetal medicine units. If you have had a previous child or pregnancy affected by congenital heart disease, you should ask your GP for a referral when you first know that you are pregnant – the early scans are performed between 11 and 14 weeks gestation.
From early-mid second trimester (14-18 weeks gestation) sonographers/doctors can get a relatively good idea of baby’s heart structure, however the people doing these early assessments need adequate skill and training. These scans are not universally available around the United Kingdom and will depend upon local expertise. In addition, sometimes the views are just too difficult to make a diagnosis, especially if mothers have a high body mass index (BMI).
It is also important to understand that the heart is still developing and even if an early scan appears normal, follow-up later in pregnancy is needed to see how the heart is growing. In addition some types of heart abnormalities can be very hard to pick up before birth.
Despite all the caveats, one of the easier features to assess at scans in early pregnancy is whether there are one or two ventricles. This is very important information for a family who may already have had a child with a single ventricle circulation. Early detection gives you a choice much earlier in pregnancy as to whether you want to continue with the pregnancy or not. It also enables you to psychologically prepare yourself, whichever choice is made.
Written by: Dr Anna Seale, Consultant Fetal and Paediatric Cardiologist, Birmingham Women’s and Children’s NHS Foundation Trust.