“I see two heartbeats!” the physician’s assistant told Sarah and Eugene Gillespie at their 8-week ultrasound.

The Clark, New Jersey couple was in shock. Twins don’t run on either side of their families and they conceived naturally. Nevertheless, they were elated to grow their brood, which includes daughter Eilish, now age 4.

At their first appointment with the maternal-fetal medicine specialist, Sarah and Eugene were told their twins were identical and were in separate amniotic sacs but shared a placenta. Some identical twins share both an amniotic sac and a placenta while others have separate amniotic sacs and placentas.  

“There were no concerns,” Eugene said. “They just said ‘Congratulations, don’t worry, it’s going to be great.’ ”

Yet at her 16-week ultrasound, Sarah knew something wasn’t right. She noticed one baby was doing flips while the other looked like he was stuck to one side of her uterus. At their appointment, the technician was supposed to write down the sex of the babies, but abruptly left the room.

“My heart sank and I thought something is off,” Sarah said.

A few minutes later, the doctor walked in and told them their babies had twin-to-twin transfusion syndrome and needed to be taken to The Children’s Hospital of Philadelphia (CHOP) right away.

The doctor explained that Sarah might be a candidate for a surgical procedure but without it, there was a 98 percent chance both of the babies would die. What’s more, although the twins had passed the tests for Down syndrome, there were concerns that one baby had a soft marker for it. And if that were true, the other baby would also have it and surgery wouldn’t be an option.

“We were both numb,” Eugene said. “We were expecting good news and the sex of the babies and our world was turned upside down.”

What is twin-to-twin transfusion syndrome?
Twin-to-twin transfusion syndrome (TTTS) is a condition whereby the blood flow between identical twins that share a placenta is unequal.

“All along the surface of the placenta, there are blood vessel connections between the two babies,” said Sarah’s surgeon, Dr. Julie Moldenhauer, medical director of the Garbose Family Special Delivery Unit and an attending obstetrician at the Center for Fetal Diagnosis and Treatment at CHOP.

Most of the time, twins are able to keep the blood flow balanced but TTTS occurs in about 15 percent of twin pregnancies that share a placenta and have two amniotic sacs, she said. The smaller, “donor” twin pumps blood to the larger, “recipient” twin, which causes the imbalance.

It’s not clear why TTTS happens but it’s often diagnosed around 16 weeks when an imbalance in amniotic fluid around the babies— one of the effects of TTTS— is seen, said Dr. Sheryl Ross, an OB/GYN at Providence Saint John’s Health Center in Santa Monica, Calif.

There are five stages of the condition, with each stage more severe than the previous. Each stage is marked by different conditions including amniotic fluid imbalance, problems with urine production, blood flow in the umbilical cord and blood vessels, and heart failure.

TTTS can often look like other conditions such as selective uterine growth restriction, structural abnormalities, or congenital heart disease. Which is why detailed anatomy ultrasounds, doppler studies and fetal echocardiograms are crucial, Moldenhauer said.

“We were living scan to scan.”
Before heading to CHOP, Sarah was monitored twice a week with ultrasounds and was told the babies were teetering between stages 1 and 2.

“We were living scan to scan,” she  said.

The likelihood that TTTS will progress from stage 1 to stage 2 is anywhere from 10 to 30 percent.

“If you progress from stage 1 to stage 2, usually it happens within a couple of weeks,” Moldenhauer said.

Left untreated, more than 90 percent of twins will die, Moldenhauer said.

Years ago, there were two surgical options to treat TTTS—amnioreduction and septostomy. The former is a minimally invasive needle procedure that removes a few liters of amniotic fluid to equalize the pressure between the two sacs. Although there’s minimal risk with this procedure, it must be done multiple times. The latter is a procedure that creates a hole in the membrane between the two sacs so the fluid can flow equally.

“The problem with these is that it doesn’t treat the underlying blood vessel connections so the outcomes weren’t that great,” Moldenhauer said.

Today, those procedures are less common and for TTTS in stage 2 and above, laser therapy is the treatment of choice because the outcomes are so much better, she said.

For the surgery, doctors trace all of the blood vessels from the donor baby into the recipient and use a laser to close the shared connections.

“It welds the blood vessels shut. So you’re not cutting the placenta apart, you’re functionally separating them,” Moldenhauer said.

The surgery has an 80 to 90 percent rate of survival for one baby and a 70 to 80 percent for both.

Surgery can be done between 16 and 26 weeks, although it’s preferable to do it after 18 weeks because there is less risk for complications.  Yet because TTTS can develop at any gestational age, there may be a small window of time left to do the surgery or it may not be an option at all.

After 24 to 26 weeks, delivery is the therapy, not surgery. And once in the NICU, is the babies' outcome is never a sure thing.

“If you deliver babies at 24 weeks who are very sick with severe twin-twin, the likelihood of survival is much less. The goal is to get the babies out far enough to survive,”  Moldenhauer said.

What’s more, although laser surgery has been used since the 1990s, it’s not clear how twins fare by 1 and 2 years of age. Experts say twins may have some neurological problems which can be as mild as needing extra help in school.

“So far our data shows that they do very well,” Moldenhauer said.

Surgery at last
Sarah finally went to CHOP three weeks after the initial diagnosis and underwent a half day of in-depth tests, which revealed that the babies were in stage 2, but there were some mild signs of stage 3.

“We were excited that we were a candidate for the [laser] procedure but it was also scary that they were progressing,” Eugene said.  

A few days later, Sarah underwent surgery to sever all of the shared connections to the placenta.

One of the risks of surgery is that even though the connections to the placenta are functionally separate, one baby— usually the donor— may be left without enough blood supply, which means one, or both could die.

“I remember being alone in the hospital room not knowing what results were going to come back. I prayed the whole time she was in there,” Eugene said.

The surgery was successful and the twins’ fluid levels gradually started to even out. Doctors also confirmed the babies didn’t have Down syndrome.

Sarah was put on bed rest for a week and was regularly monitored as the babies’ fluid levels continued to improve. Doctors estimated the twins had a 60-40 split.

At 34 weeks, Sarah’s water broke on the morning the cesarean section was scheduled.  As doctors prepped her for surgery, she broke down in tears.

“Everything hit me at once. I was an emotional wreck,” she recalled. “So far everything looked good but I felt like we don’t know for sure until they were here.”

The babies, Darren and Eoin, both a little more than 5 pounds each, stayed in the NICU for 2 weeks. Today, they’re healthy and have an endless amount of energy.

“We both feel like they’re miracle babies and we feel very blessed and very grateful,” Sarah said. “Every time we look at them, we’re reminded of the journey.”

Julie Revelant is a health journalist and a consultant who provides content marketing and copywriting services for the healthcare industry. She's also a mom of two. Learn more about Julie at revelantwriting.com.