Balloon Atrial Septostomy


Balloon atrial septostomy is a fetal procedure used to create a hole in the wall between the top chambers of the fetal heart, improving blood flow through the heart during fetal development.

The procedure is used to treat unborn babies diagnosed in utero with a congenital heart defect known as hypoplastic left heart syndrome (HLHS) with intact atrial septum, the most severe form of this complex condition.

Hypoplastic left heart syndrome is a serious condition requiring immediate intervention at birth. For these high-risk patients, fetal intervention offers an opportunity to improve the management of the condition and outcomes at birth.

What is hypoplastic left heart syndrome (HLHS) with intact atrial septum?

Hypoplastic left heart syndrome (HLHS) is a birth defect in which the left side of the heart is severely underdeveloped, leaving it too small to support blood flow to the rest of the body.  

Babies who have HLHS in utero depend on a naturally occurring hole in the wall between the top chambers of the heart, known as the atrial septum, to keep blood circulating throughout the body. In some fetuses, this hole is missing or closed, a condition known as an intact or highly restrictive atrial septum.

Without this opening, blood is unable to flow through the fetal heart. The blood backs up in the lungs, causing pulmonary hypertension (high blood pressure in the lungs) and lung damage during fetal development.

Improving Outcomes Through Early Intervention

Texas Children’s Fetal Center is one of the few centers in the world offering this fetal procedure.

The goal is to improve the stability and outcomes of these high-risk babies at birth – when fetal circulation stops and circulation in the newborn is critical for survival – enabling surgeons to begin repairing the congenital heart defect.

Outcomes for children born with HLHS are uncertain and vary greatly by patient. Most children require three heart surgeries before the age of 6.

About the Procedure

In fetal balloon atrial septostomy, a balloon or stent (hollow tube) is used to create an opening between the top chambers of the fetal heart to keep blood flowing through the heart.

During the ultrasound-guided procedure, the surgeon inserts a fine needle attached to a flexible tube (catheter) through the mother’s abdomen and uterus, through the umbilical vein and into the baby’s heart. The specialized needle is then inserted through the atrial septum (wall between the upper chambers of the heart) to create a communication or tiny opening to the left atrium.

A wire with a tiny balloon attached is then guided into the left atrium, and the hole is enlarged by gently inflating the balloon. In most cases a metal stent is also deployed to keep the hole open. The balloon is then deflated and the balloon, wire, and needle are removed.

In the first procedure of its kind, Texas Children’s Fetal Center performed this fetal intervention using a laser to create a small opening  in the atrial septum, enabling easier advancement of the needle for stent placement, with no force required. This innovative approach may now allow for stent placement even in cases involving a thick septum (wall) that were previously considered too challenging. We are currently the only center using this experimental option.

Fetal balloon atrial septostomy can be performed as early as 21 weeks of pregnancy and up to 32 or 33 weeks gestation.

HLHS circulation after birth in fetuses without an atrial septal defect (opening)

Fetal balloon atrial septostomy

Blue (deoxygenated) blood enters the right atrium from the rest of the body. This blue blood is then pumped primarily to the lungs to collect oxygen. The red (oxygenated) blood returns to the heart from the lungs into the left atrium. When the mitral valve is small, part of the underdeveloped left heart structures, and there is no atrial septal defect, the red blood has no way of getting out of the heart and delivering oxygen to the other organs.

Instead of red blood, blue blood is then pumped to the body via a residual fetal structure called the patent ductus arteriosus. This results in rapid deterioration of the newborn at birth.

HLHS circulation after birth in fetuses with an atrial septal defect (opening) created



As above, red blood enters the left atrium from the lungs. When an atrial septal defect is created through fetal intervention, the oxygenated blood can then escape the left atrium and mix with the other blood to increase the oxygen content of the blood. This mixed blood is pumped to the other organs via the patent ductus arteriosus and has adequate oxygen content for the baby to be stable until surgery several days later.

Is my baby a candidate for balloon atrial septostomy?

Balloon atrial septostomy may be recommended if your baby has been diagnosed in utero with hypoplastic left heart syndrome (HLHS) with an intact atrial septum.

Each case and each heart defect is unique, requiring close evaluation and individualized planning by a team of specialists experienced in the treatment of severe congenital heart conditions.

At Texas Children’s Fetal Center, our large multidisciplinary team includes some of the nation’s top maternal-fetal medicine specialists, congenital heart surgeons, interventional cardiologists, fetal and pediatric cardiologists, fetal imaging experts, neonatologists, pulmonologists, and maternal and fetal anesthesiologists, among others, for the treatment of fetal heart defects.

This team of experts will carefully study your case and make treatment recommendations to help your family make the most informed decisions.


As with any surgical intervention, balloon atrial septostomy involves risks, including

  • Preterm labor
  • Loss of pregnancy
  • Damage to the fetus
  • Rhythm disorder in the fetal heart
  • Fluid around the fetal heart

After the Procedure

Following the fetal procedure, mother and baby will be closely monitored throughout the remainder of the pregnancy with frequent checkups, including fetal ultrasounds and fetal echocardiograms to evaluate the baby’s development and heart condition.

The goal is for the mother to carry the baby as close to full term as possible, giving the fetal lungs, brain and other vital organs a chance to mature as much as possible prior to birth. This allows the child to become more stable before undergoing heart surgery after birth.


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 at birth to treat this rare, complex congenital heart defect.

Our Fetal Center specialists work 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.

Following delivery at Texas Children’s Pavilion for Women, newborns are transferred to Texas Children’s level IV neonatal intensive care unit (NICU), the highest level of care available for premature and critically-ill newborns, or Texas Children’s specialized cardiac intensive care unit

A First in Fetal Intervention for Congenital Heart Defects

Texas Children’s Fetal Center is the first center in the southwestern United States to create a program to treat these heart defects in utero.

Through a coordinated effort across this large, multidisciplinary team, Texas Children’s has performed in-utero fetal cardiac interventions for the full spectrum of HLHS and related conditions

Research and Clinical Trials

  • Chronic Hyperoxygenation for Borderline Left Heart – For fetuses with borderline left heart structures, where multiple left-sided heart structures are smaller than they should be, Texas Children’s Fetal Center was the first in the country to offer a research protocol in which mothers receive daily oxygen therapy throughout their third trimester. This study is ongoing.

    By delivering extra oxygen to the mother through a face mask or cannula, we hope to increase the amount of oxygen in her blood, the amount of oxygen going to the placenta and fetus, and ultimately the amount of oxygen flowing into the fetal lungs and the left side of the baby’s heart. Improving oxygen flow to the left side of the heart should improve growth as well. We are also studying the effects of extra oxygen for the fetal brain.

  • International Fetal Cardiac Intervention Registry (IFCIR) – Texas Children’s Fetal Center is one of the few specialized centers in the world performing these fetal cardiology procedures. As a member of the International Fetal Cardiac Intervention Registry, we have joined forces with other centers to evaluate and improve these still rare, complex and innovative fetal intervention procedures, improving the care and outcome for mothers and babies in pregnancies complicated by congenital heart disease in the fetus.

Learn more about our fetal cardiology research

Volumes and Outcomes


Additional Resources

Why Texas Children’s Fetal Center?

Texas Children’s Fetal Center is one of the oldest and most experienced programs in the nation. We have a history of leading the development and implementation of innovative fetal therapies and procedures such as balloon atrial septostomy, offering families new options and new hope for the treatment of rare congenital heart defects and other fetal abnormalities.

Here, you and your baby will receive expert maternal, fetal, and pediatric care, all in one state-of-the-art location. We offer extensive experience performing in-utero fetal cardiac interventions with some of the most successful outcomes in the nation.

Our Fetal Cardiology Program brings together a multidisciplinary team of experts from 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 more information or to schedule an appointment,

call Texas Children’s Fetal Center at 832-822-2229 or 1-877-FetalRx (338-2579) toll-free.

Our phones are answered 24/7. Immediate appointments are often available.