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Family Health

What Is Fetal Surgery, and How Is It Changing?

BY CARRIE MACMILLAN December 5, 2023

Yale’s Fetal Care Center director discusses advances in the field.

Being pregnant can be nerve-racking even in the best of circumstances, but any type of complication for the mother or fetus may understandably turn natural jitters into serious concern.

Fortunately, pregnant women with complications today have more treatment options compared to decades ago.

“In many cases, what was untreatable yesterday is treatable today. And it is ever-evolving,” says Mert Ozan Bahtiyar, MD, director of the Yale Fetal Care Center.

Dr. Bahtiyar is a maternal-fetal medicine specialist and a fetal surgeon. Broadly speaking, fetal surgery encompasses procedures “that allow us to change the course of a disease in a baby while it is still in the uterus,” he explains.

That can mean treating a range of conditions earlier than was previously possible, including fetal anemia (when red blood cell volume falls below normal), spina bifida (when the spinal cord doesn’t properly develop), congenital diaphragmatic hernia (in which the diaphragm doesn’t close during development), and other issues, such as twin-to-twin transfusion syndrome (an imbalance in blood flow between identical twins), and various heart conditions. And earlier treatment often means better outcomes.

Improved technology is driving most of the advances. This includes miniaturized surgical instruments, such as the fetoscope, which is inserted through a small hole in the mother’s abdomen to enter the uterus. This allows the medical provider to see the fetus and placenta, and, if needed, treat conditions or take samples.

“We also have better digital imaging, including fast fetal MRI [magnetic resonance imaging] and high-definition, next-generation ultrasounds,” Dr. Bahtiyar says. “We can detect fetal anemia as early as 16 weeks' gestation. This was not something that we treated in utero in the past. But now, it is routine to sample a baby’s blood and get results within 45 seconds."

At the Yale Fetal Care Center, a team of board-certified experts spanning maternal-fetal medicine, fetal cardiology, neonatology, genetics, pediatric surgery, and perinatal palliative care work together to develop a plan for pregnant patients and their developing babies. A care coordinator guides families through testing, specialist appointments, and anything else that is needed. After a baby is born, any additional Yale Medicine pediatric subspecialists, from pediatric cardiology to pediatric neurology, can provide additional care.

Below, we talked more with Dr. Bahtiyar about advances in fetal surgery for three different conditions.

Fetal surgery for spina bifida—in utero repair

The Yale Fetal Care Center specializes in treating a variety of complex issues that affect mother and baby, including spinal bifida, a rare condition in which a portion of the fetal spinal column doesn’t close as it should.

Of the several types of spina bifida, myelomeningocele is the most severe; a portion of the spinal cord or nerves is exposed in a sac of fluid that bulges through an opening in the baby’s back. This can lead to paralysis, hydrocephalus (a condition in which there is extra cerebrospinal fluid in and around the brain), developmental delays, and/or problems with bowel and bladder control.

Most babies born with myelomeningocele require surgery to close the sac to prevent infection, which should be done within 48 hours of birth. Now, the surgery can sometimes be done in utero.

“For the appropriately chosen cases, we can open the mother’s uterus, perform the surgery on the fetus while it is still attached to the placenta, put the fetus back in and repair the uterus, and the pregnancy continues,” Dr. Bahtiyar explains. “This in utero surgery comes with higher risks, but outcomes are significantly better than waiting and treating the baby after birth.”

When the surgery is done after birth, there is an 80% chance the baby will need to have a shunt (a hollow tube) placed in the brain to remove excess fluid. According to a study published in the New England Journal of Medicine, the in utero repair reduces the odds an infant will require a shunt to about 40%.

Congenital diaphragmatic hernia repair via fetal surgery

Congenital diaphragmatic hernia (CDH) is another condition that historically could be treated only after birth. In CDH, the diaphragm (the muscle that separates the abdomen and the chest) doesn’t fully close during development. As a result, abdominal organs can protrude into the chest cavity, which can affect lung development.

According to Dr. Bahtiyar, severe forms of this condition once carried a relatively poor prognosis, but that is no longer true. “In the past, it might lead to a situation where, after the baby is born, the survival rate was—or was expected to be—very low. It could be severely life-limiting,” he explains. “But now, we can, in utero, place a balloon temporarily in the fetus’s trachea. The fluids that accumulate behind the balloon help the lungs to expand and develop, which, in turn, helps the abdominal cavity to extend because it pushes the bowel down.”

This makes the actual postnatal repair procedure more likely to be successful, Dr. Bahtiyar notes.

Fetal anemia: diagnosis and treatment advances with fetal surgery

Fetal anemia, in which there is an insufficient number of red blood cells, is another area in which important treatment strides have been made. In the most severe cases, fetal anemia can lead to heart failure. Fetal anemia most commonly occurs when the mother and baby have incompatible blood types [also called Rh incompatibility], Dr. Bahtiyar says.

Advances in ultrasound techniques mean that doctors can now detect anemia in the womb before it leads to fetal heart failure. The treatment for this condition is an intrauterine blood transfusion.

“In the past, we would put the blood in the abdominal cavity of the fetus, and it would be absorbed from there slowly. But it was unreliable,” Dr. Bahtiyar says. “We had to use estimates on how much blood to put in, which was crude, and there was a risk of injury to the bowel.”

Now, the solution is to place a needle into the umbilical vein of the fetus. “First, we diagnose the suspected anemia through ultrasound. Then, we confirm it by taking a blood sample, and then we know how much to increase the amount of blood,” he says. “Then, very precisely, we give blood and repeat it as many times as necessary.”

Transfusion, Dr. Bahtiyar explains, corrects anemia temporarily. “This is why we need to do it multiple times during pregnancy,” he says. “The condition corrects itself after birth as the maternal antibodies, which are responsible for the anemia, wash out shortly after the baby is born.”

In some cases, such as with fetal anemia and twin-to-twin transfusion syndrome, fetal procedures can cure a problem, but in other situations, it’s more about improving the medical complication. So, it is important to realize that just because certain surgical procedures can be done while the baby is still in the womb, it is the parents’ choice as to whether one should be done.

“Sometimes, it’s about decreasing the severity of the disease when nothing can completely make it go away,” Dr. Bahtiyar says. “We are not here to make decisions for the patient. We are there to listen and to help them make decisions that are right for them.”