Aortic Stenosis


What is aortic stenosis?

Aortic stenosis is a congenital heart defect in which the aortic valve did not form properly, reducing or obstructing blood flow out of the heart.

The aortic valve is the heart valve located between the left ventricle (lower left-sided pumping chamber of the heart) and the aorta, the main artery supplying oxygen-rich blood to the body.

The aortic valve opens with each heartbeat to allow blood to flow out of the heart and into the aorta, then closes to prevent blood from leaking back from the aorta into the left ventricle. The normal valve consists of three leaflets (flaps) of near equal size.

In babies with aortic stenosis the aortic valve may be smaller and thicker than normal. The leaflets may be fused together, so instead of three leaflets, there may be only two leaflets (bicuspid aortic valve). The most severe cases of aortic stenosis may even have a single leaflet (unicuspid valve). When the leaflets are fused, they aren’t able to open normally. This results in varying degrees of blockage (stenosis) of blood flow across the aortic valve. In addition, the abnormal leaflets may not close normally, resulting in varying degrees of leakage (regurgitation).

Aortic stenosis can range from mild to severe. It can worsen over time, in some cases progressing to a severe form of heart disease called hypoplastic left heart syndrome (HLHS). HLHS is a life-threatening condition where the left side of the baby’s heart is too small or dysfunctional to use at birth. It can be associated with other defects including coarctation of the aorta.

How does aortic stenosis affect my baby?

The effects of aortic stenosis depend on the severity. The more severe the condition, the greater the consequences.

In cases where the valve opening is significantly narrowed or obstructed, the fetal heart has to work harder to pump enough blood out to the body. This places extra stress on the left ventricle. In utero, in severe cases – known as critical aortic stenosis – the left ventricle can weaken, stop growing and if left untreated, may progress to HLHS.

Babies with significant aortic stenosis may suffer from heart failure if the blockage is severe and/or if the left ventricle is unable to squeeze (pump) normally.  

Cause and Symptoms

Aortic stenosis occurs when the heart doesn’t form properly during fetal development. The cause is unknown. The condition occurs more often in males than in females. There can be a genetic association with an abnormal aortic valve (bicuspid aortic valve) which can run in families.

Babies born with less severe forms of aortic stenosis may have a heart murmur but no other symptoms. These children may not be diagnosed until later in life.

When the stenosis is severe or critical, infants can be quite ill with signs and symptoms of heart failure, including breathing difficulty, poor feeding, fatigue, irritability, and cool, pale extremities. These signs and symptoms are evident early in the newborn period.

Testing and Diagnosis

Aortic stenosis may be diagnosed during a routine prenatal ultrasound, typically at 18 to 20 weeks. Additional testing, including fetal echocardiography, is typically needed to confirm the diagnosis and learn more about the defect.

If aortic stenosis is suspected or diagnosed, prompt referral to a fetal cardiac center is important for further evaluation and to ensure proper treatment.

At Texas Children’s Fetal Center, we arrange for you to visit as quickly as possible for a comprehensive assessment by a team of specialists experienced in working together to diagnose and treat congenital heart defects, including maternal-fetal medicine physicians (experts in high-risk pregnancies), fetal cardiologists, fetal imaging experts, geneticists, interventional cardiologists, congenital heart surgeons and neonatologists.

In addition to collecting any previous diagnostic tests, additional testing may include:

Our specialists will then meet with you about the results, discuss treatment recommendations, and answer any questions your family has, to help you make the most informed decisions regarding your baby’s care and treatment.

Treatment – Before Birth

Pregnancies involving fetal aortic stenosis require close monitoring for early detection of signs the condition is worsening, including fetal non-immune hydrops (fluid accumulation in multiple areas of the baby’s body) and fetal heart failure. A fetus with aortic stenosis may have a normal sized left heart early in pregnancy that progresses to critical aortic stenosis and left heart abnormalities by mid-pregnancy.

In most cases, a fetus with aortic stenosis won’t require treatment before birth.

If the condition is expected to evolve in utero into HLHS, in select cases a fetal procedure may be considered called a balloon dilation of the aortic valve (also known as a fetal aortic valvuloplasty).

During this ultrasound-guided procedure, the surgeon inserts a special needle through the mother’s abdomen and uterus, and into the baby’s heart. A tiny balloon is then inserted across the aortic valve and gently inflated to widen a severely narrowed or blocked opening. The goal is to restore blood flow, improving the function and growth of the left ventricle and the baby’s prognosis at birth.

Following the procedure, mother and baby will be closely monitored for the remainder of the pregnancy with frequent ultrasounds and fetal echocardiograms. The baby will be delivered as close to term as possible, giving the fetal lungs, brain and other vital organs a chance to mature so the newborn is more stable before undergoing a procedure or heart surgery after birth.

Texas Children’s Fetal Center is one of the few centers in the world offering this procedure, providing new hope and more options for families facing fetal aortic stenosis. In collaboration with Texas Children’s Heart Center, our Fetal Center has successfully performed fetal balloon dilation of aortic valve since 2012. 


For the best possible outcomes, delivery should take place at a center with the highest quality congenital heart program, ensuring the expertise and resources required to treat aortic stenosis at birth, including an advanced neonatal (NICU) and cardiac intensive care unit (CICU).

Delivery and postnatal care should be carefully planned and coordinated. Our Fetal Center team works closely with Texas Children’s Heart Center every step of the way, seamlessly transitioning your baby’s care at delivery to this national leader in pediatric cardiology and heart surgery. Here, the heart specialists treating your newborn have been an integral part of their care team since before birth.

Following delivery at Texas Children’s Pavilion for Women, newborns with this condition are transferred to Texas Children’s cardiac intensive care unit for the highest level of care. 

Treatment – After Birth

Treatment is individualized for each baby based on the severity of the disease and any associated defects.

Mild cases usually require only observation. These children should have regular checkups with a cardiologist throughout their lives.

More severe cases may require intervention to reduce the degree of blockage and improve delivery of blood flow out to the body. A procedure called a cardiac catheterization may be done, where a thin, flexible tube (catheter) with a deflated balloon on the tip is put into a blood vessel, guided into the heart and placed across the valve. The balloon is then inflated to open the valve. Surgical repair or replacement are alternate possibilities.

If aortic stenosis has progressed in utero to hypoplastic left heart syndrome

at birth, treatment may involve a series of heart surgeries within the first few years of life to reroute and improve blood flow to the lungs and body while reducing the workload on the left ventricle, enabling the heart to function with one ventricle (also known as single ventricle palliation or pathway).

Depending on the severity of the condition, your baby’s postnatal care team may include:

At Texas Children’s Heart Center, our pediatric cardiologists will follow your child through adolescence, seamlessly transitioning their care at adulthood to a cardiologist who specializes in the treatment of adults with congenital heart defects.  

Why Texas Children’s Fetal Center?

  • A single location for expert maternal, fetal and pediatric care. Texas Children’s Hospital offers mothers and babies the specialized care required for the diagnosis and treatment of congenital heart conditions all in one location, for highly coordinated care and treatment planning.
  • A skilled, experienced team with proven outcomes. We have a dedicated team of maternal-fetal medicine specialists, fetal imaging experts, fetal and pediatric cardiologists, congenital heart surgeons, neonatologists and others who work in concert to care for you and your baby every step of the way, using proven protocols we’ve developed over the years. With their combined expertise and unified approach, this team offers the best possible care for pregnancies involving fetal aortic stenosis.
  • We care for your child’s cardiac needs at every stage of life, from fetus to adulthood. Our comprehensive approach starts with your first prenatal visit and continues through delivery, postnatal care, childhood and adulthood, thanks to one of the nation’s leading teams of fetal, pediatric and adult congenital heart specialists.

Texas Children’s – #1 in the Nation for Pediatric Cardiology and Heart Surgery

Our Fetal Cardiology Program is a collaboration between Texas Children’s Fetal Center and Texas Children’s Heart Center, ranked #1 in the nation for pediatric cardiology and heart surgery by U.S. News & World Report for the third consecutive year, with outcomes among the best in the country.

US NEWS Ranking Heart 2018

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Volumes and Outcomes

Research and Clinical Trials

Texas Children’s, together with our partner institution Baylor College of Medicine, constantly strives to seek new and better treatments for babies with congenital heart defects.

For more information, please contact the Cardiovascular Clinical Research Core at 832-826-2064 or email sandrea@texaschildrens.org.

Learn more about our fetal cardiology research.