Heart Block in Babies
Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist
Content reviewed against published AHA, AAP, NIH guidelines
Last reviewed:
If your baby has been diagnosed with or you suspect heart block in babies, here is what the evidence says.
The short answer
Heart block is a condition where the electrical signals that coordinate the heartbeat are delayed or blocked between the upper chambers (atria) and lower chambers (ventricles) of the heart. In babies, congenital complete heart block (third-degree) is the most significant form, causing a very slow heart rate (often 50-80 bpm in newborns compared to a normal 120-160 bpm). The most common cause is maternal autoantibodies in mothers with lupus or Sjogren syndrome, which cross the placenta and damage the baby's conduction system. Many babies with complete heart block will need a pacemaker, either at birth or during infancy.
Key takeaways
- Heart block is a condition where the electrical signals that coordinate the heartbeat are delayed or blocked between the upper chambers (atria) and lower chambers (ventricles) of the heart. In babies, congenital complete heart block (third-degree) is the most significant form, causing a very slow heart rate (often 50-80 bpm in newborns compared to a normal 120-160 bpm). The most common cause is maternal autoantibodies in mothers with lupus or Sjogren syndrome, which cross the placenta and damage the baby's conduction system. Many babies with complete heart block will need a pacemaker, either at birth or during infancy.
- Usually normal when: Your baby has a heart rate that is appropriate for their age (normal resting heart rate for newborns is 120-160 bpm, decreasing gradually through childhood)
- Call your doctor if: Your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately
- Varies by age — see the age-by-age breakdown below
“Fever itself is not an illness — rather, it is a sign or symptom that the body is fighting an infection. Fever stimulates certain defenses, such as the white blood cells, which attack and destroy invading bacteria.”
Parents everywhere have the same worry. You are doing the right thing by looking into it.
What Parents Should Know
According to AHA, AAP, NIH guidelines, heart block is a condition where the electrical signals that coordinate the heartbeat are delayed or blocked between the upper chambers (atria) and lower chambers (ventricles) of the heart. In babies, congenital complete heart block (third-degree) is the most significant form, causing a very slow heart rate (often 50-80 bpm in newborns compared to a normal 120-160 bpm). The most common cause is maternal autoantibodies in mothers with lupus or Sjogren syndrome, which cross the placenta and damage the baby's conduction system. Many babies with complete heart block will need a pacemaker, either at birth or during infancy. At Prenatal, congenital heart block is often detected prenatally when fetal bradycardia (slow heart rate) is identified during routine monitoring or ultrasound. Fetal heart rates below 100 bpm warrant urgent evaluation with fetal echocardiography. The most common cause is anti-SSA/Ro and anti-SSB/La antibodies from the mother, even in mothers who have no symptoms of autoimmune disease. If detected, the pregnancy is closely monitored by maternal-fetal medicine and pediatric cardiology. Some cases may warrant maternal treatment with dexamethasone. It is generally considered normal when your baby has a heart rate that is appropriate for their age (normal resting heart rate for newborns is 120-160 bpm, decreasing gradually through childhood). However, you should contact your pediatrician promptly if your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately.
Normal vs. Concerning
When to Seek Immediate Care
- Your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately
- Your baby or child with a pacemaker becomes suddenly lethargic, has a very slow pulse, faints, or appears pale or gray -- the pacemaker may be malfunctioning, call 911
- Your baby has episodes of prolonged pauses in heartbeat, unresponsiveness, or seizure-like activity -- call 911
By Age
What to expect by age
Prenatal
Congenital heart block is often detected prenatally when fetal bradycardia (slow heart rate) is identified during routine monitoring or ultrasound. Fetal heart rates below 100 bpm warrant urgent evaluation with fetal echocardiography. The most common cause is anti-SSA/Ro and anti-SSB/La antibodies from the mother, even in mothers who have no symptoms of autoimmune disease. If detected, the pregnancy is closely monitored by maternal-fetal medicine and pediatric cardiology. Some cases may warrant maternal treatment with dexamethasone.
0-3 months
Newborns with congenital complete heart block have a ventricular rate typically between 50-80 bpm. Some babies tolerate this well initially, while others show signs of heart failure including poor feeding, lethargy, and breathing difficulty. An ECG confirms the diagnosis, showing atrial and ventricular rhythms that are independent of each other. Babies with heart rates below 55 bpm, signs of heart failure, or associated structural heart defects typically need pacemaker implantation in the first days to weeks of life.
3-12 months
Infants with complete heart block who were stable at birth may be monitored closely with regular ECGs, Holter monitors, and echocardiograms. If the ventricular rate remains adequate and the baby is feeding well and growing, pacemaker implantation may be deferred. However, if the heart rate drops further, the baby shows signs of exercise intolerance (tiring during feeds), or the heart begins to enlarge, a pacemaker becomes necessary. In small infants, the pacemaker leads are typically placed on the outside of the heart (epicardial) rather than through the veins.
1-3 years
Toddlers with pacemakers generally lead active, normal lives with some precautions. The pacemaker generator is typically placed in the abdomen in young children. Parents learn to check the pulse and recognize signs that the pacemaker may need adjustment. Children with pacemakers need to avoid strong magnets and certain medical equipment (MRI may require special protocols). Regular pacemaker checks (in-office or remote monitoring) are essential.
3+ years
Older children with pacemakers can participate in most activities, though contact sports may need modification to protect the pacemaker generator. The pacemaker battery will eventually need replacement (typically every 5-10 years depending on use). As children grow, lead revisions or conversions from epicardial to transvenous systems may be needed. Long-term outcomes for children with congenital heart block and pacemakers are generally excellent.
What to Tell Your Pediatrician
- Describe when you first noticed heart block in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if you have lupus, Sjogren syndrome, or are known to carry anti-SSA/Ro or anti-SSB/La antibodies and are pregnant or planning pregnancy.
- Mention if your baby's heart rate seems consistently slower than expected during well-baby visits.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
What Should You Do?
When to take action
- Your baby has a heart rate that is appropriate for their age (normal resting heart rate for newborns is 120-160 bpm, decreasing gradually through childhood)
- Your baby has first-degree heart block (a minor prolongation of conduction time) that the pediatrician or cardiologist says is benign
- Your child with a pacemaker is growing well, active, and meeting developmental milestones
- You have lupus, Sjogren syndrome, or are known to carry anti-SSA/Ro or anti-SSB/La antibodies and are pregnant or planning pregnancy
- Your baby's heart rate seems consistently slower than expected during well-baby visits
- Your child with a pacemaker seems less active than usual or is having more fatigue
- Your child with known heart block has not had a cardiology follow-up or pacemaker check in over 6 months
- Your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately
- Your baby or child with a pacemaker becomes suddenly lethargic, has a very slow pulse, faints, or appears pale or gray -- the pacemaker may be malfunctioning, call 911
- Your baby has episodes of prolonged pauses in heartbeat, unresponsiveness, or seizure-like activity -- call 911
What You Can Do at Home
- Keep track of when you notice heart block in babies — noting the time of day, duration, and any triggers can help your pediatrician.
- Remember that your baby has a heart rate that is appropriate for their age (normal resting heart rate for newborns is 120-160 bpm, decreasing gradually through childhood) — this is generally within the range of normal.
- At Prenatal, focus on observation rather than intervention unless your pediatrician advises otherwise.
- Follow any care instructions from your pediatrician. Keep a written log of symptoms to bring to appointments.
- While monitoring at home, seek immediate care if your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately.
Related Conditions
Congenital Heart Defect Signs in Babies
Congenital heart defects (CHDs) are the most common type of birth defect, affecting about 1 in 100 babies. They range from small holes in the heart that may close on their own to complex defects requiring multiple surgeries. Early detection through pulse oximetry screening and recognizing key signs — such as blue skin, rapid breathing, poor feeding, and failure to gain weight — is critical. Advances in surgery have dramatically improved survival and quality of life.
Baby Heart Murmur - Innocent vs Concerning
Heart murmurs are very common in children - up to 75% of children will have an audible murmur at some point. The vast majority are "innocent" or "functional" murmurs, meaning there is no structural heart problem. These murmurs are simply the sound of blood flowing normally through the heart and are more audible during fever, illness, or excitement. A smaller number of murmurs indicate a structural heart difference that may need monitoring or treatment. Your pediatrician can usually distinguish between the two and will refer for an echocardiogram if there is any concern.
My Baby Turns Blue (Cyanosis)
Blue or purple discoloration limited to a baby's hands and feet (acrocyanosis) is very common in newborns and usually harmless, caused by immature circulation. However, blue coloring of the lips, tongue, face, or trunk (central cyanosis) is always a medical emergency that requires immediate evaluation, as it may indicate a heart or lung problem.
Related Resources
Frequently asked questions
Is heart block in babies normal?
When should I call the doctor about heart block in babies?
When is heart block in babies normal?
What causes heart block in babies?
What should I mention to my pediatrician about heart block in babies?
Is heart block in babies normal at Prenatal?
Is heart block in babies normal at 0-3 months?
Should I go to the ER for heart block in babies?
Does heart block in babies go away on its own?
References
Doctor Visit Checklist
Bring this checklist to your next pediatrician visit to discuss Heart Block in Babies.
Things to mention
- Describe when you first noticed heart block in babies and how it has changed over time.
- Note your baby's current age and which age-specific patterns you are seeing.
- Mention if you have lupus, Sjogren syndrome, or are known to carry anti-SSA/Ro or anti-SSB/La antibodies and are pregnant or planning pregnancy.
- Mention if your baby's heart rate seems consistently slower than expected during well-baby visits.
- Let your doctor know if you have noticed any related concerns, such as changes in feeding, sleep, or movement patterns.
- Bring a list of any questions or observations you want to discuss at the appointment.
Observations to share
- You have lupus, Sjogren syndrome, or are known to carry anti-SSA/Ro or anti-SSB/La antibodies and are pregnant or planning pregnancy
- Your baby's heart rate seems consistently slower than expected during well-baby visits
- Your child with a pacemaker seems less active than usual or is having more fatigue
Urgent signs to report immediately
- Your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately
- Your baby or child with a pacemaker becomes suddenly lethargic, has a very slow pulse, faints, or appears pale or gray -- the pacemaker may be malfunctioning, call 911
- Your baby has episodes of prolonged pauses in heartbeat, unresponsiveness, or seizure-like activity -- call 911
My notes
From ismybabyalright.com — free, evidence-based baby health guides
All content follows our editorial policy and is reviewed against published clinical guidelines.
2,705 evidence-based guides6 authoritative medical sources5 medical advisory board members
Related Resources
Bottom line
Most cases of heart block in babies are normal. Talk to your pediatrician if your newborn has a very slow heart rate (below 80 bpm) with poor feeding, lethargy, or difficulty breathing -- seek emergency care immediately.
Trust your instincts. If something feels wrong, reach out to your pediatrician. Worrying about your baby means you care — that is a good thing.
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Related Medical Concerns
Congenital Heart Defect Signs in Babies
Congenital heart defects (CHDs) are the most common type of birth defect, affecting about 1 in 100 babies. They range from small holes in the heart that may close on their own to complex defects requiring multiple surgeries. Early detection through pulse oximetry screening and recognizing key signs — such as blue skin, rapid breathing, poor feeding, and failure to gain weight — is critical. Advances in surgery have dramatically improved survival and quality of life.
Baby Heart Murmur - Innocent vs Concerning
Heart murmurs are very common in children - up to 75% of children will have an audible murmur at some point. The vast majority are "innocent" or "functional" murmurs, meaning there is no structural heart problem. These murmurs are simply the sound of blood flowing normally through the heart and are more audible during fever, illness, or excitement. A smaller number of murmurs indicate a structural heart difference that may need monitoring or treatment. Your pediatrician can usually distinguish between the two and will refer for an echocardiogram if there is any concern.
My Baby Turns Blue (Cyanosis)
Blue or purple discoloration limited to a baby's hands and feet (acrocyanosis) is very common in newborns and usually harmless, caused by immature circulation. However, blue coloring of the lips, tongue, face, or trunk (central cyanosis) is always a medical emergency that requires immediate evaluation, as it may indicate a heart or lung problem.
My Baby's Head Shape Looks Abnormal
Many babies develop temporary head shape irregularities that are completely normal. A cone-shaped head from vaginal delivery reshapes within days. Mild positional flattening (plagiocephaly) from sleeping on the back is very common and usually improves with repositioning and tummy time. However, head shape changes involving ridges, a persistently bulging fontanelle, or rapid head growth changes should be evaluated to rule out craniosynostosis.
Achondroplasia (Dwarfism) in Babies
Achondroplasia is the most common form of short-limbed dwarfism, affecting about 1 in 15,000 to 40,000 births. It is caused by a mutation in the FGFR3 gene and is usually apparent at birth with characteristic features including short limbs, a larger head, and a prominent forehead. Intelligence is normal. With monitoring for specific complications and supportive care, children with achondroplasia lead full, active, and independent lives.
Adenoid Hypertrophy and Breathing
Adenoids are lymphoid tissue located behind the nose that help fight infection in young children. When adenoids become enlarged (adenoid hypertrophy), they can block the nasal airway, causing chronic mouth breathing, snoring, nasal speech, and sleep-disordered breathing. Enlarged adenoids are most common between ages 2-7 and are a leading cause of obstructive sleep apnea in young children. Treatment ranges from watchful waiting and nasal steroids to surgical removal (adenoidectomy) if breathing or sleep is significantly affected.