Can a baby develop heart block while still in the womb? Yes. Fetal heart block affects the electrical signals that coordinate the baby’s heartbeat. Understanding what the term means can help parents discuss scan findings with their maternity team.
Heart block refers to delayed or interrupted electrical conduction inside the heart. A suspected rhythm problem needs specialist assessment.
Understanding your baby’s heartbeat
Your baby’s heart has a built-in electrical conduction system. This system coordinates the upper and lower chambers so they work together to pump blood.
The word “block” describes a problem with signal transmission. Ask your doctor which part of the rhythm is affected and how the scan findings relate to your baby’s condition.
What is fetal heart block?
The heart has two upper chambers, called atria, and two lower chambers, called ventricles. Normally, an electrical impulse starts in the heart’s natural pacemaker and travels through a conduction pathway to coordinate their contractions.
When conduction between the atria and ventricles is delayed or interrupted, it is called atrioventricular heart block. In complete heart block, the upper and lower chambers beat independently, and the ventricles usually beat more slowly.
Are there different types?
- First degree: Signals reach the ventricles more slowly than usual.
- Second degree: Some signals do not reach the ventricles.
- Third degree, or complete heart block: Signals from the atria do not conduct to the ventricles.
The degree of block helps specialists assess its significance and plan care.
What can cause fetal heart block?
Some cases are associated with maternal anti-Ro/SSA or anti-La/SSB antibodies that cross the placenta and affect the developing conduction system. These antibodies can be associated with autoimmune conditions such as lupus or Sjögren syndrome. Other cases occur with structural heart abnormalities.
Tell your obstetrician about autoimmune conditions, known antibody results or a previously affected pregnancy. Your team can decide whether additional assessment is appropriate.
Watch the doctor explain
Watch the Nisarga Diagnostics reel: “ಗರ್ಭದಲ್ಲಿರುವ ಮಗುವಿಗೆ Heart Block ಆಗುತ್ತಾ?”
A closer look with fetal heart assessment
If a rhythm concern is found, ask whether a fetal echocardiogram is recommended, who will perform the assessment and when it should take place.
Bring earlier scan reports so your specialist can review the findings in context. Ask for an explanation of any unfamiliar terms, including atrial rate, ventricular rate and degree of block.
How is fetal heart block diagnosed?
An unexpectedly slow heartbeat during a prenatal assessment may prompt further investigation. Fetal echocardiography allows specialists to compare atrial and ventricular activity and examine the baby’s heart. A heart-rate reading alone cannot establish the diagnosis.
Keep your recommended pregnancy scan appointments. Our guide to NT and anomaly scan preparation explains what to bring. If a finding is identified, read about discussing pregnancy scan abnormalities with your specialist.
What happens after diagnosis?
Care may involve fetal medicine, paediatric cardiology and newborn specialists. Monitoring and delivery planning depend on the degree of block, heart function and associated findings. Treatment during pregnancy is considered individually; complete heart block often requires a pacemaker after birth. Long-term cardiology follow-up is important.
Make a clear follow-up plan
Before leaving your consultation, write down the next review date, any investigations advised and the specialist you should see. Keep your reports together so they are available at future appointments.
If a referral has been recommended, ask how soon it is needed and whom to contact with questions between appointments. Having a clear plan helps families understand the next steps.
Questions to ask your specialist
- Has heart block been confirmed, or is further assessment needed?
- What degree of block has been identified?
- Are there any associated findings in the heart?
- Do I need antibody testing or a review of previous results?
- When should the next heart assessment take place?
- Does this change where my baby should be delivered?
- What care might my baby need after birth?
The answers depend on the individual pregnancy. Use your own reports and your specialist’s explanation when discussing care, rather than comparing with another family’s experience.
Frequently asked questions
Can heart block be detected before birth?
Yes. Fetal echocardiography can identify abnormal coordination between the upper and lower heart chambers.
Does every baby with heart block need the same treatment?
No. Management depends on the type of block and the baby’s overall cardiac assessment.
What should I do if my baby’s movements decrease?
Contact your maternity team promptly. Do not wait for the next appointment. Our guide on tracking baby movements explains why changes deserve attention.
Is fetal heart block the same as a blocked blood vessel?
No. It concerns electrical conduction between the heart chambers. The term does not mean that an artery is blocked.
Why are the upper and lower heart rates different?
In complete heart block, signals from the atria do not reach the ventricles. The lower chambers rely on a slower backup rhythm.
Can maternal antibodies be involved?
Yes. Anti-Ro/SSA and anti-La/SSB antibodies can be associated with fetal heart block. Your doctor decides whether testing is appropriate.
Who should review a suspected fetal heart block?
Assessment may involve fetal medicine and paediatric cardiology specialists, with newborn specialists helping plan care after delivery.
Will my baby need a pacemaker?
Some babies, particularly those with complete heart block, need a pacemaker. The decision depends on the rhythm, heart function and specialist assessment.
Can treatment during pregnancy reverse complete heart block?
Established complete heart block is generally irreversible. Prenatal treatment decisions need specialist review; do not start medicines on your own.
Is follow-up needed after birth?
Yes. Babies with congenital heart block need cardiac assessment after birth and ongoing follow-up with a paediatric cardiologist.
What if a previous pregnancy was affected?
Discuss this before another pregnancy with a fetal medicine specialist. They can review recurrence risk and plan individual monitoring.
What should I bring to the appointment?
Bring your prescription, previous pregnancy scan reports, relevant blood-test results and a list of medicines. Note your questions and any previous affected pregnancy.
Discuss your scan findings
Bring your prescription, previous reports and relevant medical history to Nisarga Diagnostics, Sanjaynagar, Bengaluru. Ask your treating doctor whether fetal heart assessment or specialist referral is needed.
This article provides general education and does not replace individual medical advice.
Medical references: Children’s Hospital of Philadelphia: Heart Block; ISUOG: Congenital Heart Block.
Founder of Nisarga Diagnostics, is a renowned fetal ultrasound specialist with over 20 years of expertise. An alumnus of Government Medical Colleges in Mysore and Bangalore, he also holds a D.N.B. from the National Board of Examinations, Delhi, and certification from the Fetal Medicine Foundation, London. A former Professor and HOD, he has trained countless PG students and junior radiologists, shaping the future of fetal imaging in India.