Heart murmurs in newborns

It’s estimated that up to 85 percent of newborns have some sort of heart murmur and it often isn’t as serious as it sounds, with the vast majority of them clearing spontaneously within 48 hours of the birth.

You’ll likely have heard your own heartbeat so you’ll be familiar with the ‘ba-boom’ sound it makes. A heart murmur is an extra sound made by the blood as it travels through the blood vessels in the heart, and is heard via stethoscope in between the heart’s normal beating.

It can manifest as a whole range of sounds, from swishing to clicks, but all are described as heart murmurs. They can happen for several reasons and be harmless (the clinical term for these is ‘innocent’) or, rarely, related to a problem with your baby’s heart (defined as a (‘pathologic’ heart murmur). Most heart murmurs are benign, so don’t panic if your doctor says your newborn baby has one.

Innocent heart murmurs

This is the most common type of heart murmur and the one most usually present in newborn babies. These are usually related to the fact that your baby didn’t have to breathe for herself before she was born. This means that the blood vessels to her lungs are small and narrow. Once she’s born and needs to take in oxygen by breathing, blood flow to her lungs increases, but as the blood vessels are still very narrow the blood has to force itself through, causing a murmur as it does so. This type of murmur doesn’t indicate any structural problems with the heart, so it poses no health risk to your newborn.

Pathologic heart murmurs

This type of heart murmur is more serious and is caused by defects in the heart or its valves. In children, the most common form of this heart murmur is ventricular septal defect (VSD). If your baby has this it means she has a hole in the wall (septum) between the upper or lower chambers of her heart, meaning they’re connected when they should be separate. The murmur is the sound of blood flowing through this connection.

A pathologic heart murmur can also be cause by problems with heart valves – if these are too narrow (called stenosis) blood can’t flow smoothly through them and this will cause a murmur. Rarely a murmur can be caused by a heart muscle disorder such as cardiomyopathy, which makes the heart muscle abnormally thick and prevents it from pumping blood properly.

How is it treated?

Most innocent heart murmurs are detected when your doctor listens to your newborn’s heart during her standard newborn checks but if the sound of the murmur is at all different your baby may need to have a special test called an electrocardiogram (ECG), which checks the electrical activity of the heart, to check if the murmur is pathological. If there is still any question, you will be referred to a cardiologist who may perform an echocardiogram, which is an ultrasound of the heart. This will show how blood is circulating through your baby’s heart.

Your doctor will also keep a close eye on how your baby is growing. Pathological heart murmurs tend to affect a newborn’s growth because they mean that the heart has to work harder, and the energy that would usually go towards growth is diverted to the heart instead. Along with failure to thrive, signs that a heart murmur may be serious include rapid breathing, difficulty feeding due to breathlessness, paleness, a blue tinge to your newborn’s lips (called cyanosis, this indicates a lack of oxygen in the blood).

The information in this feature is intended for educational purposes only. If you have any concerns about your health, the health of your child or the health of someone you know, please consult with a doctor or other healthcare professional.

Last Modified: 27/11/2008