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Dr. Alessandro Giardini
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Your baby is hours old and already there's a word on the discharge notes no new parent wants to see. A murmur found at the newborn examination is one of the most common reasons a family leaves hospital with a follow-up appointment already booked, and it's also one of the most misunderstood findings in those first exhausting days.
Newborn murmurs are common for a specific reason, not just by chance. In the days right after birth, a baby's circulation is still finishing its switch from the womb to independent life outside it. A structure called the ductus arteriosus, which let blood bypass the lungs before birth, is in the process of closing. While it closes, and for a short window afterward, blood flow through it can produce an audible, temporary sound. This alone explains a large share of the murmurs heard in the first day or two of life, and it typically settles on its own within days without anything needing to be done.
That said, newborns are examined with a lower threshold for further checks than older children, and there's a good reason for that. A newborn can't tell you how they feel, obviously, and structural heart conditions can occasionally be present without any other obvious sign in the very first days, before the circulation has fully settled into its longer-term pattern. This is exactly why UK newborn screening includes both a clinical examination and, increasingly, pulse oximetry (a simple oxygen-level check using a sensor on the hand or foot), aimed at catching conditions that might not yet produce an audible murmur or a visible symptom.
In most units, the paediatrician will note it down, examine the baby fully for anything else, feeding difficulty, unusual colour, breathing pattern, and then decide whether to arrange a repeat check before discharge, a follow-up at a few weeks of age, or a referral for an echocardiogram. Many babies are simply reassessed at the routine six-to-eight-week check, by which point a purely transitional murmur has usually gone, closing the question without any imaging being needed at all.
Persistence past that point, rather than the initial finding itself, is often what prompts a referral to a paediatric cardiologist. A murmur still there at six weeks is more likely to reflect something structural than one heard only in the first forty-eight hours, though even then, most turn out to be harmless variants rather than anything needing treatment.
Feeding is one of the clearest things parents can watch for themselves in the meantime, and it's something they should keep an eye on. A baby who tires quickly during a feed, sweats while feeding, breathes noticeably fast, or struggles to gain weight at the rate expected should be reviewed sooner rather than waiting for a scheduled check, whether or not a murmur was ever mentioned.
It's worth adding something that comes up constantly with new parents in clinic. Hearing the word "murmur" attached to your days-old baby is frightening in a way that's hard to prepare for, however many times you're told the odds are good. That reaction doesn't need justifying to anyone in the room.
Both directions are common and usually come down to the ductus arteriosus closing over the first days of life. A murmur heard at birth often disappears as this structure closes fully, while a murmur that shows up later reflects the circulation settling into its longer-term pattern and becoming easier or harder to hear at different stages.
Not automatically, but in practice the threshold to undertake an echocardiogram in a weeks old child is low. Some transitional newborn murmurs can watched clinically first, with an echocardiogram kept for murmurs that persist, come with any symptoms, or raise concern on examination. Dr Giardini can advise directly whether imaging makes sense for your baby.
Yes, patent ductus arteriosus in particular is more common and often takes longer to close in babies born early, because the structure that normally shuts shortly after birth is more likely to stay open longer in a premature circulation.
On rare occasions, some conditions simply don't produce an audible murmur, which is exactly why pulse oximetry screening was brought in alongside clinical examination, to catch a small number of conditions that listening alone can't always pick up.
A newly noticed murmur at a later check is common and usually still harmless, but any new murmur in an older baby is worth a proper look rather than assuming it's the same transitional sound heard in other newborns.
Author: Dr. Alessandro Giardini, MD, PhD, Consultant Paediatric Cardiologist
Written 05/08/2026
Last reviewed 05/08/2026