Medical Conditions

Atrioventricular Septal Defect (AV Canal) in Babies

Medically reviewed by Dr. Michael Okonkwo, MD, FAAP · Board-Certified Neonatologist

Content reviewed against published CDC, AAP, AHA guidelines

Editorial policy

Last reviewed:

If your baby has been diagnosed with or you suspect atrioventricular septal defect (av canal) in babies, here is what the evidence says.

The short answer

An atrioventricular septal defect (AVSD), also called an AV canal defect or endocardial cushion defect, is a heart defect involving holes between the upper and lower chambers of the heart and abnormalities of the valves between the chambers. In a complete AVSD, there is essentially one large hole in the center of the heart with a single common valve. AVSD is strongly associated with Down syndrome -- about 40-50% of babies with Down syndrome have some form of heart defect, and AVSD is the most common type. Symptoms include rapid breathing, poor feeding, poor weight gain, and frequent respiratory infections. Surgical repair is typically performed between 3-6 months of age.

Key takeaways

  • An atrioventricular septal defect (AVSD), also called an AV canal defect or endocardial cushion defect, is a heart defect involving holes between the upper and lower chambers of the heart and abnormalities of the valves between the chambers. In a complete AVSD, there is essentially one large hole in the center of the heart with a single common valve. AVSD is strongly associated with Down syndrome -- about 40-50% of babies with Down syndrome have some form of heart defect, and AVSD is the most common type. Symptoms include rapid breathing, poor feeding, poor weight gain, and frequent respiratory infections. Surgical repair is typically performed between 3-6 months of age.
  • Usually normal when: Your baby has been evaluated with echocardiography and the heart structure is normal
  • Call your doctor if: Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation
  • 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.”
— Fever and Your Child, American Academy of Pediatrics (AAP)

This is one of the most common questions parents ask. Searching for answers means you care.

What Parents Should Know

According to CDC, AAP, AHA guidelines, an atrioventricular septal defect (AVSD), also called an AV canal defect or endocardial cushion defect, is a heart defect involving holes between the upper and lower chambers of the heart and abnormalities of the valves between the chambers. In a complete AVSD, there is essentially one large hole in the center of the heart with a single common valve. AVSD is strongly associated with Down syndrome -- about 40-50% of babies with Down syndrome have some form of heart defect, and AVSD is the most common type. Symptoms include rapid breathing, poor feeding, poor weight gain, and frequent respiratory infections. Surgical repair is typically performed between 3-6 months of age. At Prenatal, aVSD may be detected during a fetal echocardiogram, particularly if Down syndrome is suspected or confirmed. Prenatal diagnosis allows for planning delivery at a facility with pediatric cardiac services. Parents will typically meet with a pediatric cardiologist before birth to discuss the defect, expected course, and surgical plan. Prenatal counseling helps families prepare for what to expect after delivery. It is generally considered normal when your baby has been evaluated with echocardiography and the heart structure is normal. However, you should contact your pediatrician promptly if your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation.

Sources: [1], [2], [3]

Normal vs. Concerning

Usually Normal
Worth Discussing
Your baby has been evaluated with echocardiography and the heart structure is normal
Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation
Your baby with Down syndrome has had cardiac screening and no defect was identified
Your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency
Your child has had successful AVSD repair and their cardiologist reports the heart is functioning well
Your child after AVSD repair develops new rapid breathing, swelling, or sudden decline in activity level -- seek emergency care
Your baby has a small, partial (incomplete) AVSD that the cardiologist is monitoring and says does not yet require intervention
Your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects

When to Seek Immediate Care

  • Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation
  • Your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency
  • Your child after AVSD repair develops new rapid breathing, swelling, or sudden decline in activity level -- seek emergency care

By Age

What to expect by age

Prenatal

AVSD may be detected during a fetal echocardiogram, particularly if Down syndrome is suspected or confirmed. Prenatal diagnosis allows for planning delivery at a facility with pediatric cardiac services. Parents will typically meet with a pediatric cardiologist before birth to discuss the defect, expected course, and surgical plan. Prenatal counseling helps families prepare for what to expect after delivery.

0-3 months

Babies with a complete AVSD may initially appear well, but as the normal drop in pulmonary vascular resistance occurs in the first weeks of life, increasing blood flow to the lungs leads to symptoms. Signs include rapid or labored breathing, poor feeding, sweating during feeds, and poor weight gain. The baby may have a heart murmur detected by the pediatrician. An echocardiogram confirms the diagnosis. Medications such as diuretics may be started to manage symptoms while awaiting surgical repair.

3-6 months

Surgical repair of a complete AVSD is usually performed between 3-6 months of age, before irreversible damage to the lung blood vessels can occur. The surgery involves closing the holes with patches and reconstructing the two AV valves (mitral and tricuspid) from the single common valve. Surgery is performed under general anesthesia with cardiopulmonary bypass. Hospital recovery typically takes 1-2 weeks. Most children do very well after repair.

6-12 months post-repair

After successful AVSD repair, most babies show significant improvement in feeding, weight gain, and breathing. Regular cardiology follow-up monitors for residual holes, valve leakage (especially the mitral valve), and heart rhythm problems. Some children may need additional procedures later if valve leakage becomes significant. Growth and development typically improve dramatically after repair.

Long-term

Most children who have had AVSD repair live active, normal lives. Long-term follow-up with a cardiologist is needed to monitor valve function, as the reconstructed mitral valve may develop leakage over time and occasionally requires reoperation. Children with Down syndrome and repaired AVSD receive integrated care addressing both their cardiac needs and developmental support. Endocarditis prophylaxis may be recommended for dental procedures in the first 6 months after surgery.

What to Tell Your Pediatrician

  • Describe when you first noticed atrioventricular septal defect (av canal) 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 your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects.
  • Mention if your baby seems to tire during feeds, gains weight slowly, or breathes faster than other babies.
  • 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

Probably normal when...
  • Your baby has been evaluated with echocardiography and the heart structure is normal
  • Your baby with Down syndrome has had cardiac screening and no defect was identified
  • Your child has had successful AVSD repair and their cardiologist reports the heart is functioning well
  • Your baby has a small, partial (incomplete) AVSD that the cardiologist is monitoring and says does not yet require intervention
Mention at your next visit when...
  • Your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects
  • Your baby seems to tire during feeds, gains weight slowly, or breathes faster than other babies
  • Your child after AVSD repair is having more respiratory infections or seems less active than expected
Act now when...
  • Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation
  • Your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency
  • Your child after AVSD repair develops new rapid breathing, swelling, or sudden decline in activity level -- seek emergency care

What You Can Do at Home

  • Keep track of when you notice atrioventricular septal defect (av canal) in babies — noting the time of day, duration, and any triggers can help your pediatrician.
  • Remember that your baby has been evaluated with echocardiography and the heart structure is normal — 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 baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation.

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.

Down Syndrome Baby Development

Down syndrome (trisomy 21) is the most common chromosomal condition, affecting about 1 in 700 babies. Children with Down syndrome typically reach all developmental milestones — sitting, walking, talking — but on their own timeline, which is often later than typical peers. With early intervention, supportive therapies, and appropriate medical care, children with Down syndrome lead fulfilling, active lives.

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.

Milestone

Month-by-Month Development

Detailed monthly development guides from birth through 24 months.

Guide

When to Call the Doctor

General guide on when to call the pediatrician, visit urgent care, or go to the ER.

Frequently asked questions

Is atrioventricular septal defect (av canal) in babies normal?
An atrioventricular septal defect (AVSD), also called an AV canal defect or endocardial cushion defect, is a heart defect involving holes between the upper and lower chambers of the heart and abnormalities of the valves between the chambers. In a complete AVSD, there is essentially one large hole in the center of the heart with a single common valve. AVSD is strongly associated with Down syndrome -- about 40-50% of babies with Down syndrome have some form of heart defect, and AVSD is the most common type. Symptoms include rapid breathing, poor feeding, poor weight gain, and frequent respiratory infections. Surgical repair is typically performed between 3-6 months of age.
When should I call the doctor about atrioventricular septal defect (av canal) in babies?
Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation Your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency Your child after AVSD repair develops new rapid breathing, swelling, or sudden decline in activity level -- seek emergency care
When is atrioventricular septal defect (av canal) in babies normal?
Your baby has been evaluated with echocardiography and the heart structure is normal Your baby with Down syndrome has had cardiac screening and no defect was identified Your child has had successful AVSD repair and their cardiologist reports the heart is functioning well
What causes atrioventricular septal defect (av canal) in babies?
An atrioventricular septal defect (AVSD), also called an AV canal defect or endocardial cushion defect, is a heart defect involving holes between the upper and lower chambers of the heart and abnormalities of the valves between the chambers. In a complete AVSD, there is essentially one large hole in the center of the heart with a single common valve. AVSD is strongly associated with Down syndrome -- about 40-50% of babies with Down syndrome have some form of heart defect, and AVSD is the most common type. Symptoms include rapid breathing, poor feeding, poor weight gain, and frequent respiratory infections. Surgical repair is typically performed between 3-6 months of age. Common explanations include: Your baby has been evaluated with echocardiography and the heart structure is normal. Your baby with Down syndrome has had cardiac screening and no defect was identified.
What should I mention to my pediatrician about atrioventricular septal defect (av canal) in babies?
You should mention atrioventricular septal defect (av canal) in babies at your next visit if: Your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects. Your baby seems to tire during feeds, gains weight slowly, or breathes faster than other babies. Your child after AVSD repair is having more respiratory infections or seems less active than expected.
Is atrioventricular septal defect (av canal) in babies normal at Prenatal?
AVSD may be detected during a fetal echocardiogram, particularly if Down syndrome is suspected or confirmed. Prenatal diagnosis allows for planning delivery at a facility with pediatric cardiac services. Parents will typically meet with a pediatric cardiologist before birth to discuss the defect, expected course, and surgical plan. Prenatal counseling helps families prepare for what to expect after delivery.
Is atrioventricular septal defect (av canal) in babies normal at 0-3 months?
Babies with a complete AVSD may initially appear well, but as the normal drop in pulmonary vascular resistance occurs in the first weeks of life, increasing blood flow to the lungs leads to symptoms. Signs include rapid or labored breathing, poor feeding, sweating during feeds, and poor weight gain. The baby may have a heart murmur detected by the pediatrician. An echocardiogram confirms the diagnosis. Medications such as diuretics may be started to manage symptoms while awaiting surgical repair.
Should I go to the ER for atrioventricular septal defect (av canal) in babies?
Seek emergency care if your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation, or if your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency. When in doubt, call your pediatrician's after-hours line for guidance.
Does atrioventricular septal defect (av canal) in babies go away on its own?
In many cases, atrioventricular septal defect (av canal) in babies resolves on its own, especially when your baby has been evaluated with echocardiography and the heart structure is normal. By Long-term, most children who have had AVSD repair live active, normal lives. Long-term follow-up with a cardiologist is needed to monitor valve function, as the reconstructed mitral valve may develop leakage over time and occasionally requires reoperation. Children with Down syndrome and repaired AVSD receive integrated care addressing both their cardiac needs and developmental support. Endocarditis prophylaxis may be recommended for dental procedures in the first 6 months after surgery.
CDCAAPAHA

References

  1. [1]Centers for Disease Control and Prevention. Facts about Atrioventricular Septal Defect. CDC, 2024. CDC
  2. [2]American Academy of Pediatrics. Atrioventricular Canal Defect. HealthyChildren.org. AAP
  3. [3]American Heart Association. Atrioventricular Canal Defect. AHA, 2024. AHA

Doctor Visit Checklist

Bring this checklist to your next pediatrician visit to discuss Atrioventricular Septal Defect (AV Canal) in Babies.

Things to mention

  • Describe when you first noticed atrioventricular septal defect (av canal) 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 your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects.
  • Mention if your baby seems to tire during feeds, gains weight slowly, or breathes faster than other babies.
  • 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

  • Your baby with Down syndrome has not yet had an echocardiogram -- all babies with Down syndrome should be screened for heart defects
  • Your baby seems to tire during feeds, gains weight slowly, or breathes faster than other babies
  • Your child after AVSD repair is having more respiratory infections or seems less active than expected

Urgent signs to report immediately

  • Your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation
  • Your baby's lips or skin appear blue or gray, especially during feeds or at rest -- this is a medical emergency
  • Your child after AVSD repair develops new rapid breathing, swelling, or sudden decline in activity level -- seek emergency care

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

Ear Infection TriageWell-Baby Visit PrepEmergency ContactsBaby Tracker

Bottom line

Most cases of atrioventricular septal defect (av canal) in babies are normal. Talk to your pediatrician if your baby has rapid or labored breathing, poor feeding, sweating during feeds, and is not gaining weight -- these signs suggest heart failure and require urgent evaluation.

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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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.

Down Syndrome Baby Development

Down syndrome (trisomy 21) is the most common chromosomal condition, affecting about 1 in 700 babies. Children with Down syndrome typically reach all developmental milestones — sitting, walking, talking — but on their own timeline, which is often later than typical peers. With early intervention, supportive therapies, and appropriate medical care, children with Down syndrome lead fulfilling, active lives.

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.

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