Fetal Heart Scanning

Within Harris Birthright there is now a unit dedicated specifically to detailed examination of the fetal heart. The fetal cardiac unit integrates skills and experience in congenital heart disease with those in fetal medicine to optimise the detection and management of heart abnormalities in the fetus, whether they be primary abnormalities of the heart or disturbances of heart function related to other fetal conditions.

•  What is congenital heart disease?

Malformations of the heart account for the majority of heart disease in the fetus and in children. There are a wide variety of individual conditions ranging from simple holes connecting heart chambers to complex abnormalities in which one of the heart chambers is effectively absent or vessels and chambers are abnormally connected or obstructed. Less common are abnormalities in the heart rhythm, where the heart rate is too fast, too slow, or irregular and abnormalities of the heart muscle, in which the heart fails to contract normally.

• Why scan the fetal heart?

Structural congenital heart disease is relatively common, occurring in about 8 per thousand live-born babies. Of these, about 5 per thousand could be identified in the fetus by expert level fetal heart scanning. Moreover, those heart abnormalities that can be detected pre-natally are the more severe ones, with the most profound influence on the survival and well being of the child.

Abnormalities of the heart often occur as part of conditions such as Down’s syndrome and many other conditions associated with mental retardation. An examination of the fetal heart is therefore an essential part of the complete evaluation when any abnormality has been recognised on a scan. Conversely, the reassurance derived from a normal detailed anomaly scan is only fully substantiated if the fetal heart has been examined in detail.

Scan of a fetal heart

•  Why is a special unit necessary?

Most hospitals offer routine ultrasound screening at about 20 weeks, which usually includes examination of a simple 4-chamber view of the heart and may identify some, but not all, major heart abnormalities. In many serious heart defects however, the 4-chamber view of the heart is entirely normal. Therefore a more detailed examination of the heart, including the connections of the major blood vessels and Doppler estimation of flow through the valves, is necessary to be confident about excluding most significant abnormalities. It is therefore appropriate that those at increased risk of having a fetus with a congenital heart abnormality should be offered a specialist fetal heart scan. Also, when an abnormality of the heart is suspected on a routine anomaly scan the abnormality should be confirmed and precisely defined in a specialist centre.

Advances in cardiac surgery over recent years mean that there are now only a few rare congenital heart abnormalities for which no treatment can be offered. The outlook for various types of abnormality is however very different. Small but important details in complex abnormalities can have a major influence on the type of surgery possible and the likelihood of success. In addition to detailed analysis of the structure and function of an abnormal fetal heart it is therefore important to use this information to provide prospective parents with an accurate prediction of the likely outlook for their babies condition. In this respect, it is not only the chance of survival that is important, but also the quality of life that may be expected for survivors. Close and continuing links with the paediatric cardiology department at Guy’s, including weekly meetings with the cardiac surgeons to discuss cases, ensures that the fetal cardiology unit at King’s remains in tune with new developments in treatment.

•  Who requires a specialist fetal heart scan?

Certain women can be identified as being at higher than average risk of having a fetus affected by congenital heart disease for the following reasons.

1. Suspicion of a heart anomaly on a routine scan, or failure to adequately demonstrate a normal 4-chamber view of the heart on a routine anomaly scan.
2. Increased thickness of nuchal fluid on an early (12-week) scan.
3. Either parent or another close relative having congenital heart disease.
4. Diabetes in the mother.
5. Exposure of the fetus to drugs such as lithium, anticonvulsants or alcohol in early pregnancy.
6. Demonstration of any extra-cardiac abnormality in the fetus, such as exomphalos or cleft palate, that might conceivably be part of a syndrome.
7. Abnormal fetal heart rhythm.
8. Multiple pregnancy

However, most congenital heart disease occurs in women in whom there are no reasons to expect an increased risk. It has therefore been our policy at Harris Birthright to ensure that a detailed fetal heart scan is performed by a doctor with special experience and expertise in every woman who attends for detailed fetal anomaly scanning, even in the absence of any identifiable risk factors.