How common are heart defects?
Over 150,000 adults in the UK have congenital heart disease. Every year 5000 babies are born in the UK, about 12 a day, with significant cardiac (heart) abnormalities. This means about 1 in every 25 newborn babies. Cardiac defects are more common in newborn babies than Down’s Syndrome, which occurs in about 1 in 650 newborn babies. About half of cardiac babies will need urgent assessment and specialised care.
How are heart defects picked up in pregnancy?
There are four main chances to pick uo heart defects in pregnancy
- Nuchal Translucency Scan (11-13 weeks)
- Anomaly Scan (20 weeks)
- Cardiac Scan (24+ weeks)
- Pulse Oximetry (Newborn)
Nuchal Translucency Scan (11-12 weeks)
Most women will have a Dating Scan at around 12 weeks to identify that the pregnancy is viable, the age and due date, the number of babies present and some major abnormalities. A Nuchal Translucency Scan additionally measures the amount of tissue fluid at the back of the baby’s neck and combined with a blood test can be used to screen for Down’s Syndrome, but in addition if the measurement is more than 3.5mm there is also an increased risk of cardiac abnormalities in the baby. About a third of babies later found to have a cardiac abnormality will have had an increased NT measurement.
Anomaly Scan at 20 weeks – One View and Three View Cardiac Scans
A detailed Anatomy Scan at around 20 weeks is offered to screen for abnormalities in the baby including cardiac defects but at this time the heart is still only the size of a pea and the detection rates are poor across the UK.
Originally most hospitals check only One View, the “4 Chamber View”, which has been around for about 20 years and looks at the four main pumping chambers (left and right atria and left and right ventricles). The 4-chamber view is still the most crucial view, as it takes into account the heart’s size/position and examines in detail the four pumping chambers (for disproportion), walls & septum.
The “4 Chamber View” will generally pick up about half of fetal cardiac anomalies. However, just looking at the 4-chamber view can result in missing important problems such as Tetralogy of Fallot, “hidden” septal defects which are; holes in the midline wall that divides the left and right side of the heart, Transposition of the Great Arteries (TGA) where the main vessels supplying the lungs and the body come off the wrong chambers, and arch defects such as Coarctation where the aorta – the main vessel supplying the body- is constricted limiting the blood supply to the baby’s body.
Nowadays all NHS Hospitals perform Three Views by also checking the left and right outflow tracts. The right ventricular outflow tract, “RVOT” supplies blood through the Pulmonary Artery to the lungs (after birth). The left ventricular outflow tract, “LVOT” supplies blood through the Aorta to the upper body.
Tiny Tickers – Five View Cardiac Scan
Tiny Tickers, the UK Charity whose aim is to “improve the detection of heart disease before birth and give these babies a better start in life”, advocates that all pregnant women should be routinely offered a Five View Cardiac Scan, which will pick up most cardiac abnormalities.
What is a Five View Cardiac Scan?
This scan uses a conventional ultrasound probe to systematically sweep through five main views of the heart to look for any abnormalities. It includes the 4 Chamber View and the two outflow tract views (LVOT and RVOT). The two additional views, however, add important further information about the development of the heart. It also uses Colour Flow Doppler, which shows the flow of blood through the valve.
Cardiac Scans Fetal Echo
The ultimate way to screen for cardiac defects is to have a full fetal echo by a Paediatric Cardiologist. As well as looking at the 5 standard views of the heart, the blood flow through the heart and valves is assessed in detail and can check if the flow is excessive, reduced or if there is back flow (regurgitation) through an abnormal valve.
Fetal Echo Service in Cardiff?
Innermost Healthcare launched a private Fetal Echo Service in 2013 with a full Fetal Echo at around 24 weeks of pregnancy by a a Consultant Paediatric Cardiologist, Mr Orhan Uzun.