A baby’s heart is supposed to race by adult standards, and most readings that alarm parents fall inside what’s normal for a small, growing body. Crying, fever, and activity push the rate up and it settles once the cause passes. A rate that stays high while the baby is calm, or comes with changes in how the baby looks or acts, can point to an illness that needs care. So the number on its own matters less than what the baby was doing when it was taken and how the baby seems overall.
What Counts as a Normal Heart Rate for a Baby
- Resting infant: about 100 to 160 bpm (beats per minute).1Dr Alessandro Giardini. Palpitations in Babies and Toddlers: What Parents Need to Know
- Crying or actively feeding: up to about 180 bpm.2Dr Alessandro Giardini. Palpitations in Babies and Toddlers: What Parents Need to Know
- Crying newborn: can briefly go slightly above 180 bpm.3Apollo Pharmacy. Newborn Baby Heart Rate & Pulse: Normal Range Chart by Activity
Babies run fast because their hearts are small, each beat pushes out less blood, and they have less blood overall.4Cleveland Clinic. Heart Rate and Kids: How High Is Too High? Over the first two years the nervous system matures and gains better control to slow the heart, so resting rates drift downward as your child grows.
If you want to check your baby’s pulse yourself, wait until the baby is calm or asleep, not mid-cry. Feel the inside of the upper arm or watch the chest, count for 30 seconds, and double it. Count again a few minutes later to confirm the first number. Write down the time, the number, and what the baby was doing.
A healthy baby’s heart rate shifts from minute to minute, rising with a wriggle or a noise and dipping in deeper sleep. Smart socks and oximeters often show a number the instant the baby moves, so a brief spike during a kick or stir is common and usually means little. Readings taken in the same state, such as asleep and settled, tell you far more than a sleeping number set beside a feeding number.
Everyday Reasons a Baby’s Heart Speeds Up
Fever, pain, crying, and agitation all raise a baby’s heart rate as a normal response.5Dr Alessandro Giardini. Palpitations in Babies and Toddlers: What Parents Need to Know Crying makes a baby breathe harder, use more muscle, and need more oxygen.6Apollo Pharmacy. Newborn Baby Heart Rate & Pulse: Normal Range Chart by Activity In newborns, crying raises the heart rate by about 19 beats a minute on average.7PubMed. Cardiopulmonary changes in the crying neonate Once the baby is soothed, the pulse should come back to its resting range.8Apollo Pharmacy. Newborn Baby Heart Rate & Pulse: Normal Range Chart by Activity
Fever raises heart rate by about 10 beats a minute for each 1°C (1.8°F) rise in temperature.9PubMed. The relationship between body temperature, heart rate and respiratory rate in children Doctors use this rule to judge whether fever alone explains a fast heart or something else is going on.10PubMed. The relationship between body temperature, heart rate and respiratory rate in children Babies vary widely, though, so the same fever can mean very different rates in two babies.11PubMed. How much tachycardia in infants can be attributed to fever?12PubMed. How much tachycardia in infants can be attributed to fever?
You can do a rough version of this at home. A baby at 39°C is about 2°C above the usual 37°C, so fever alone would add roughly 20 beats a minute to the baby’s usual calm rate. Add that to the resting rate for a rough ceiling. A rate far above it suggests something besides the fever is contributing and is worth mentioning to a doctor. Treat this as a guide, not a precise cutoff. To check again, wait until the baby is calm after fever medicine and cooling have had time to work, then recount. A rate that stays high once the temperature falls points away from fever as the cause.
A reassuring pattern has a few parts. After crying or feeding stops and the baby is comforted, the pulse settles back toward the resting range within a few minutes. The baby feeds normally, keeps up the usual number of wet diapers, and has healthy pink color. Between fussy spells the baby is alert, makes eye contact, and responds to you.
Illnesses That Can Keep the Heart Rate High
As a baby dries out, the heart speeds up to keep blood flowing with less fluid.13PubMed. Heart rate to identify non-febrile children with dehydration and acute kidney injury in emergency department: a prospective validation study A fast heart with few wet diapers, vomiting, or diarrhea can be a sign of dehydration. Count wet diapers: noticeably fewer than usual over a day is one of the most useful signs that a baby isn’t taking in enough fluid. Look for a dry mouth and for crying with few or no tears. Gently look at the soft spot on top of the head; if it looks sunken while the baby is calm and upright, that is one sign of fluid loss among several. Unusual sleepiness, floppiness, or being hard to engage together with a fast heart is a reason to seek care promptly.
Infection can also keep the rate up. In newborns in intensive care, a persistently fast heart rate can be an early sign of serious blood infection (sepsis).14Pediatric Research. Vital signs as physiomarkers of neonatal sepsis In a very young baby, a high rate with fever or poor feeding needs a doctor’s check.
When newborns get too little oxygen, their heart rate rises in the first minute.15PubMed Central. Chemoreceptor reflexes in the new-born infant: effects of varying degrees of hypoxia on heart rate and ventilation in a warm environment Anemia, too few red blood cells, also makes a baby’s heart beat faster, especially in premature babies.16PubMed. Myocardial, erythropoietic, and metabolic adaptations to anemia of prematurity in infants with bronchopulmonary dysplasia In premature babies, the heart rate falls after a blood transfusion corrects the anemia.17PubMed Central. Effects of anaemia on haemodynamic and clinical parameters in apparently stable preterm infants
An overactive thyroid in newborns causes a fast heart, poor feeding, irritability, tremors, sweating, and poor sleep.18PubMed Central. The tortuous diagnosis of one case of neonatal hyperthyroidism Some babies are born with heart defects that bring a fast heart along with fast breathing.19Cardiology in the Young. The pathogenesis of heart failure in infants with congenital heart disease
Breathing medicines such as salbutamol (albuterol) can cause a fast heart, and higher doses cause more.20PubMed Central. Adverse effects of bronchodilators in infants with bronchiolitis A faster heart soon after a treatment is a known side effect, not a sign the treatment is failing, and it usually eases over a few hours as the dose wears off. Tell the doctor if the rate seems extreme, the baby seems jittery or shaky, or it doesn’t settle as expected. Don’t change or skip a dose on your own; ask the doctor or pharmacist what to do.
Heart Rhythm Problems Like SVT
Not every fast heart rate in a baby is SVT (supraventricular tachycardia), a rhythm problem where the heart’s electrical signal loops and races.21Dr Alessandro Giardini. Palpitations in Babies and Toddlers: What Parents Need to Know In babies, the signs are often subtle: paleness, bluish color, restlessness, irritability, trouble feeding, fast breathing, sweating, and grunting.22PubMed. Supraventricular tachycardia in the neonate and infant About 80% of SVT in babies under 1 comes from an extra electrical pathway in the heart.23PubMed. Supraventricular tachycardia in the neonate and infant
SVT often starts and stops abruptly, while a crying-related rise builds as the baby gets upset and fades as the baby settles. The rate is often well above what crying produces, and it tends to stay at a similar high level instead of rising and falling. It doesn’t slow down when the baby is comforted, fed, or held, which is the key contrast with a harmless cause.
A heart that races for a long time can weaken.24PubMed. Predictors of myocardial recovery in pediatric tachycardia-induced cardiomyopathy It often improves fully or partly once the heart rate is controlled.25PubMed Central. Tachycardia-Induced Cardiomyopathy in an Infant with Atrial Flutter and Prolonged Recovery of Cardiac Function
If you suspect an episode, count and note the rate and how long it lasted. Take a short video of the baby’s chest and color if you can. Call the doctor promptly, or 911 if danger signs appear.
When to Call 911 or See a Doctor
- Fainting or being hard to wake.26Ann & Robert H. Lurie Children’s Hospital of Chicago. Tachycardia (Fast Heart Rate) in Children
- Trouble breathing, such as muscles pulling in between the ribs or nostrils flaring with each breath.27Norton Children. Is your child’s heart beating fast? Here’s what to do.
- Pale or gray skin, or blue lips.28Norton Children. Is your child’s heart beating fast? Here’s what to do.
Little babies with heart trouble may be irritable for no reason, refuse to eat, or vomit after eating.29Norton Children. Is your child’s heart beating fast? Here’s what to do. A high rate that stays up while the baby is calm, or comes with these changes, deserves a same-day call.
Babies under 3 months with fever need prompt medical review. Premature babies, or those with known heart defects, warrant a lower threshold to call.
When you reach the nurse line, give the rate you counted and say what the baby was doing, such as asleep, calm, or crying. Report the temperature and how long the baby has been unwell. Describe feeding and the number of wet diapers over the last day. Mention any color changes or breathing effort.
Can You Trust a Smart Sock or Baby Monitor
In tests against hospital equipment, one popular smart sock performed inconsistently, and another monitor gave false low pulse readings and missed low oxygen.30CBC News. How smart is the use of a smart baby monitor? A single alarming number on a consumer monitor should be confirmed by checking the baby yourself.
When the monitor alarms, look at the baby first: color, breathing, and whether the baby responds to you. Check that the sensor is fitted properly and hasn’t slipped, since poor contact is a common cause of false readings. Count the pulse by hand to compare with the display. Act on how the baby looks, not on the app. A pink, breathing, responsive baby with an odd number is different from a baby who looks unwell with a normal number. A normal reading doesn’t rule out illness if the baby seems unwell.
How Doctors Check a Fast Heart Rate
An ECG (or EKG) records the heart’s electrical signals and gives results right away.31Riley Children’s Health. Supraventricular Tachycardia in Children A Holter monitor is a portable ECG worn for 24 hours or more, including at home.32Riley Children’s Health. Supraventricular Tachycardia in Children An event monitor records over a longer stretch to catch episodes that come and go.33Riley Children’s Health. Supraventricular Tachycardia in Children
The ECG uses painless stickers on the chest and takes only a few minutes, as long as the baby is kept fairly still. The doctor may first check temperature, hydration, and oxygen level, because those often explain a fast rate. If the heart itself looks normal, blood tests may look for infection, anemia, or thyroid problems.
Fast Heart Rate Before Birth
Doctors may diagnose fetal tachycardia when the baby’s heart rate stays or sometimes goes above 180 bpm.34Cincinnati Children’s Hospital Medical Center. Fetal Tachycardia | Types, Causes and Treatment Some hospitals reserve the term abnormally fast for rates over 200 bpm.35GOSH Hospital site. Prenatal ultrasound showing fetal tachycardia Caffeine and dark chocolate a parent eats can make the baby’s heart more active on monitoring.36PubMed. The effects of maternal caffeine and chocolate intake on fetal heart rate
A single fast moment on a scan is often rechecked later instead of treated, since a baby’s rate changes with movement. Ask your provider which number they consider concerning, since hospitals differ. Mention recent coffee or chocolate before monitoring so the reading can be interpreted fairly. A rate that stays high may lead to a more detailed heart scan of the baby.