This leaflet is to help you understand what Aortic stenosis is, what tests you need and the implication of being diagnosed with Aortic stenosis for your baby and your family.

What is Aortic Stenosis?

Aortic stenosis is a congenital heart defect (present from birth) that occurs during the first eight weeks of pregnancy. In a healthy heart, the left heart ventricle, one of the pumping chambers of the heart, pumps blood rich in oxygen into the aorta, the main artery that distributes blood to the body. The aortic valve, located between the left ventricle and the aorta, regulates blood flow. When the aortic valve becomes abnormally narrow, it restricts blood flow from the left ventricle. This condition is known as Aortic Valve Stenosis.

How does Aortic Stenosis happen?

Significant aortic stenosis is relatively uncommon, affecting about 6 in every 1000 babies born. It can occur alone or in combination with other heart abnormalities. Aortic stenosis occurs due to improper development of the aortic valve during the early part of fetal growth. The normal aortic valve has three thin and flexible leaflets. In cases of aortic stenosis, the valve leaflets are thickened or become less pliable and fuse together. Most commonly, the abnormality occurs when the aortic valve has two instead of three leaflets, called a bicuspid aortic valve. The exact cause as to why this happens is not known. Most of the time this heart defect occurs by chance with no apparent reason for its development. However, sometimes it can have a genetic link and occur more often in certain families.

Should I have more tests done?

You may be referred to or request fetal echocardiography, a specialised ultrasound of the baby's heart during pregnancy, or a detailed fetal scan by a fetal medicine specialist. You might be offered genetic counseling with a specialist in genetic conditions, and genetic testing. Genetic testing can include an amniocentesis (where a thin needle is used to take some of the amniotic fluid in the womb) which is then examined to look for chromosomal abnormalities, as well as Chromosomal Microarray (CMA, or “chip”) or exome sequencing, which are advanced tests that look more closely at the genetic make-up of the fetus.

What are the things to watch for during the pregnancy?

Babies with aortic stenosis require frequent ultrasound by a fetal medicine specialist and a paediatric cardiologist, if available, to monitor the progression of the condition. When the aortic valve does not open normally, the muscles of the left ventricle must work harder to pump blood into the aorta. As the pregnancy progresses, the valve obstruction can become more significant. To compensate for this increased workload the muscles of the left ventricle gradually thicken. If the valve is severely obstructed, the muscles of the left ventricle may not be able to compensate and may fail to pump blood into the aorta. In some cases, with progression, the left ventricle becomes small and non-functioning.

In certain severe cases of aortic stenosis, some very specialised centers can perform a surgical procedure on the fetus during pregnancy, called aortic valvuloplasty, to widen the narrow valve. The goal is to improve blood flow and promote better heart development before birth, to improve the prognosis for the baby. You can discuss with your caregiver whether this might be right for your baby.

Knowing these findings in advance can help your doctor and the care team to decide what delivery plan will be best for you and your baby. One in 10 babies with aortic stenosis is born with significant narrowing that requires emergency treatment at birth.

What does it mean for my baby after it is born?

A baby with aortic stenosis should be delivered in a tertiary center with neonatal intensive care, paediatric cardiology, and paediatric cardiothoracic facilities, if possible. This allows coordination of care and permits access to emergency services in the immediate newborn period if needed. Vaginal delivery is usually recommended and caesarean section is reserved for obstetric indications.

Depending on the severity of the baby’s condition, the paediatric cardiologist will decide what treatment baby would require after birth. Some of these possible treatment pathways would have been discussed with you during pregnancy. Treatment would depend on the size and function of the left pumping chamber. In some cases, the baby might require a small operation to relieve the obstruction. If the left pumping chamber is very small in size, the baby might need a series of operations to increase the blood flow to the body and bypass the poorly functioning left pumping chamber.

Overall outcomes for isolated aortic stenosis are excellent. Children should receive follow-up over time, into adulthood, to make sure the narrowing within the aorta does not get worse.

Will it happen again?

There is a slightly higher chance of this condition happening again in the next pregnancy. Genetic studies have shown that there is a 13%-15% recurrence risk of aortic stenosis in a baby if the mother is affected, a 5% risk if the father is affected, and a 2% risk if one child in the family is affected. When the heart defect recurs in another child, it is not always the same heart defect: it may be something minor or more severe.

In your next pregnancy, you can benefit from a detailed fetal heart examination early in the pregnancy (if facilities are available) or at the time of a routine fetal anomaly scan at 19-20 weeks.

What other questions should I ask?

  • Does the baby’s heart look normal?
  • How often will I have ultrasound examinations done?
  • What is the severity of the aortic stenosis?
  • What are the chances of this condition to progress in the course of pregnancy?
  • Where should I deliver?
  • Where will the baby receive the best care after it is born?
  • Can you give an indication of the duration of the hospital stay after surgery?
  • Can I meet in advance with the team of doctors that will be looking after my baby when it is born?


Last updated: July 2024

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Aortic Stenosis