About 2%–4% of newborns have a detectable heart murmur in the first days of life, and most early murmurs are harmless.
Hearing a “whoosh” during a newborn check can rattle any parent. A heart murmur is simply the sound of blood moving through the heart or nearby vessels. In the first days after birth, circulation is shifting from womb life to breathing air, so extra sounds are often common. The real question people ask is frequency, risk, and what to do next.
Heart Murmur In Newborns: How Common Is It Today?
Across large nursery studies and clinical guidelines, reported rates vary because of timing, examiner skill, and how strictly a murmur is defined. Many babies have no audible sound at all before discharge, some have a soft, short murmur that fades, and a small share have a finding linked to a heart condition that needs follow up.
| Timing/Setting | Reported Share | Notes |
|---|---|---|
| First 24–48 hours, routine exam | ~2%–4% | Many resolve within days as lung blood flow rises. |
| Immediate post-birth period | <1% in some series | Quiet rooms and brief exams can miss soft sounds. |
| Any time in infancy | Up to ~8.6% | Most infant murmurs are “innocent” or transient. |
One helpful plain-English summary for families is this: a newborn murmur is not rare, yet a serious heart defect is much less common. Congenital heart disease appears in about 1 in 100 births, and only a portion are the “critical” types that cause low oxygen early on. Universal pulse oximetry checks catch many of those cases before a baby goes home.
Why A Murmur Shows Up In The Newborn Period
Right after delivery, pressure in the lungs falls, the ductus arteriosus begins to close, and flow patterns flip toward the normal newborn circulation route. Turbulence during this transition can create a short, soft systolic sound. Common benign causes include pulmonary branch stenosis of the tiny branch arteries and a small patent ductus arteriosus that is still closing.
Less often, the sound reflects a structural problem such as a ventricular septal defect, coarctation of the aorta, or outflow tract issues. The bedside exam looks at more than noise: oxygen saturation, pulses in the legs, skin color, feeding effort, and breathing pattern carry more weight than loudness alone.
Newborn Heart Murmur Prevalence: What The Research And Guidelines Say
Modern primary care guidance notes that up to 8.6% of infants have a murmur during early life, while most school-age kids will have one at some point. That context explains why most newborn murmurs end up being benign, while a few signal disease. For screening, the American Academy of Family Physicians advises referral of newborns with a murmur to a pediatric cardiology service because early murmurs are harder to classify at the bedside.
Hospitals also run pulse-ox checks for critical congenital heart disease. You can read the latest algorithm on the CDC’s online clinical page on pulse-ox newborn screening. For a clinician-level overview of infant murmurs and when to refer, see the AAFP review of heart murmurs in children.
How Clinicians Sort Innocent And Pathologic Murmurs
What Listeners Hear
Features that point toward an innocent pattern include a soft grade (1–2/6), short duration, systolic timing, normal oxygen saturations, normal femoral pulses, and a well-appearing baby who feeds without sweating or breathlessness. A pathologic pattern is more likely with a harsh or loud sound, diastolic components, an abnormal second heart sound, differences in arm-to-leg pulses, low oxygen, or any sign of poor perfusion.
What A Grade Means
Clinicians use a six-point scale. Grades 1–2 are faint to soft; grade 3 is moderately loud without a thrill; grade 4 adds a palpable thrill; grade 5 is loud with minimal contact; grade 6 can be heard with the stethoscope barely touching. Even so, grade alone cannot label a murmur safe or unsafe.
Why Oxygen Numbers Matter
Pulse oximetry looks for silent hypoxemia. A pre- and post-ductal reading helps detect a difference between the right hand and a foot. A wide gap can point toward duct-dependent flow. This objective check pairs with the exam and guides whether an echocardiogram is needed the same day.
Why Reported Rates Differ
Newborn circulation changes by the hour. A baby examined at two hours of life may have no audible sound, yet a soft murmur can appear at twelve hours as the ductus narrows. Room noise, baby position, crying, and the examiner’s experience all affect detection. That is why the literature shows ranges from less than one percent right after birth in some series to around four percent over the first two days, with higher figures when counting any murmur during infancy.
Another reason the numbers swing: not every heart condition creates a murmur on day one. Some obstructive lesions and mixing lesions reveal themselves first through low oxygen or weak pulses not by noise. Screening bundles that include pulse-ox and careful pulse checks counter that blind spot. That is why teams rely on both ears and numbers, not sound alone during early newborn care.
What Parents Can Expect During Evaluation
Most nurseries follow a stepped plan. First comes a careful exam with pulse-ox readings in the right hand and one foot. If numbers are normal and the baby looks well, staff often repeat auscultation after several hours because transitional murmurs fade as the ductus closes. If the sound persists, if oxygen numbers look low, or if pulses are weak, teams call pediatric cardiology and arrange imaging.
When the echo is normal, families usually go home with simple guidance and an outpatient recheck. If a small ventricular septal defect or a closing ductus is found, clinicians set a follow-up plan; many close on their own and need nothing more than growth monitoring.
Common Diagnoses Linked To A Newborn Murmur
Transitional or innocent patterns: pulmonary branch stenosis, closing ductus sounds, and tiny physiologic shunts that settle as pressures change. These tend to be soft, short, and left upper sternal border in location.
Small ventricular septal defect: a frequent finding on early echocardiograms. Many close over months to years. Growth tracking and periodic reviews are standard, with no activity limits for most babies.
Outflow or arch issues: such as coarctation of the aorta or pulmonary stenosis. These may present with weak leg pulses, a blood pressure difference between limbs, or low oxygen. Early diagnosis leads to care plans and close monitoring.
Red Flags That Need Same-Day Care
Call your baby’s clinician or birth unit promptly if you notice any of the signs below. These clues matter far more than whether a murmur sounds loud or soft to a listener.
| Sign | What It May Indicate | Next Step |
|---|---|---|
| Blue color around lips or tongue | Possible low oxygen | Seek urgent assessment now. |
| Fast breathing or pauses | Work of breathing or poor flow | Go to emergency care. |
| Poor feeding, sweating with feeds | Potential low cardiac output | Call the on-call team today. |
| Cool legs or weak leg pulses | Flow obstruction to the body | Immediate hospital check. |
| Excessively sleepy or hard to rouse | Possible low perfusion | Emergency visit right away. |
Practical Tips While You Wait For A Follow-Up
- Track feeds, diapers, breathing pattern, and color; bring notes to your visit.
- Keep scheduled pulse-ox or echo appointments; timing helps catch changes.
- Offer frequent, shorter feeds if the baby tires; that eases the work of eating.
- Ask for clear discharge instructions about who to call and where to go after hours.
How This Differs From Murmurs In Older Infants And Children
The newborn window stands apart. Circulatory pathways are still settling, which helps explain why the newborn heart murmur prevalence sits in the low single digits during the first two days, then rises when counting any time in infancy. By preschool years, many kids have had an innocent murmur during a fever, a growth spurt, or while lying down at a routine visit. The first hours after birth are when teams watch closely for duct-dependent lesions and oxygen drops. That difference drives separate goals: early newborn checks aim to detect critical defects, while later visits mostly encounter benign, transitional sounds.
What An Echocardiogram Checks
Structural Survey
An echo is an ultrasound of the heart. It shows chamber sizes, wall motion, valve motion, and the size and shape of the great arteries. Color Doppler displays flow across valves and between chambers, which helps identify shunts or obstruction. The sonographer captures many angles so the cardiologist can review in detail.
What Follow-Up Looks Like At Home
Daily life usually needs only small adjustments. Feed the baby on demand. Keep them warm and well rested. If a clinician gives a home oxygen number to watch for, learn the plan for readings and when to seek help. Write down any spells of blue color, extra sleepiness, or breathing trouble and share those notes at the next visit. If a murmur fades and the child grows well, visits return to the standard schedule.
Bottom Line For New Parents
In plain terms, how common is a heart murmur in newborns? Based on nursery audits and pediatric guidance, roughly 2%–4% of babies have a detectable murmur in the first days, a minority have one right after birth, and a larger share will have a murmur at some point in infancy. Most early sounds are transitional. Screening with pulse oximetry plus a careful exam keeps babies safe by flagging the rare heart defect that needs early treatment.