BY CHERYL ALKON

IDENTICAL TWINS KHLOE AND KARLEE ARE THRIVING AFTER IN UTERO SURGERY TO CORRECT TWIN-TO-TWIN TRANSFUSION SYNDROME.

Photography by Gregg Goldman

When 23-year-old Kelly Easton, an identical twin, learned she was carrying identical twins in her first pregnancy, she was following the path her mother had taken years before. When routine prenatal testing done halfway through the 20th week of Kelly’s pregnancy revealed her developing fetuses had twin-to-twin transfusion syndrome (TTTS), the syndrome was familiar to her. Kelly’s mother was diagnosed with TTTS when she was pregnant with Kelly and her twin sister.

What is twin-to-twin syndrome?

Also known as TTTS, the syndrome occurs in about 10% to 15% of all monochorionic pregnancies, in which identical twins share one placenta. It is caused by an imbalance in blood flow across the placental blood-vessel connections that help sustain the twins. As a result of this imbalance, one twin becomes severely dehydrated and the other overhydrated.

Every shared placenta has these blood-vessel connections, but why some cause an imbalance in fluid is unknown, says Kathy Bligard, MD, MA, WashU Medicine maternal-fetal medicine specialist at Barnes-Jewish Hospital. Dr. Bligard also is associate director of the hospital’s Fetal Care Center, a partnership between Barnes-Jewish Hospital, St. Louis Children’s Hospital, and WashU Medicine Physicians. She notes that there is no known genetic link that might explain why, in Kelly’s case, two generations of the same family experienced TTTS.

Women with monochorionic twin pregnancies typically have ultrasound imaging every two weeks, beginning around week 16 and continuing through delivery, Dr. Bligard says. These images allow specialists to observe, among other things, the level of amniotic fluid in the uterus. An imbalance in amniotic fluid, “caused when one baby stops urinating and the other urinates a lot,” says Dr. Bligard, can be visualized during an ultrasound and, when present, can prompt a diagnosis of TTTS. “In mild cases, we can see a difference in fluid levels from fetus to fetus.” If the imbalance is more severe—if one fetus stops making urine altogether or if there is evidence that the imbalance is affecting either fetus’s heart—“we usually intervene within 24 hours.” Intervention involves using a minimally invasive procedure that helps both fetuses thrive.

Illustrations courtesy of Maury Aaseng

Treatment for twin-to-twin syndrome

Barnes-Jewish Hospital, working with its WashU Medicine Physician partner, is the only hospital in Missouri that treats TTTS using minimally invasive fetal laser surgery—a procedure done in utero (while the fetuses are still in the uterus) that corrects the imbalance of fluids so that both fetuses can thrive. Nationwide, there are about 50 centers offering the in utero procedure, though some states have no centers while others have several.

During the procedure, the surgeon makes a small incision, about a tenth of an inch long, in the mother’s abdomen, then inserts a tiny camera inside the uterus used to locate all the placental blood vessels that connect the twins. The vessels are then sealed off and ablated using a small laser. “As best we can, we are trying to divide a single placenta into two separate ones,” Dr. Bligard says. After the procedure, mothers stay overnight at the hospital and are monitored for signs of premature labor.

Without surgery, there is a 90% risk that one or both fetuses will not survive. With surgery, both fetuses have a 70% to 90% chance of surviving. Before in utero laser surgery for TTTS became the standard of care in the mid-to-late 2000s, women with the syndrome, including Kelly’s mother, were most often treated with a series of amnioreduction procedures, during which excess amniotic fluid is removed from the uterus. That form of treatment does not treat the underlying cause of TTTS, and the risk of preterm delivery is much higher, though Kelly and her sister were delivered safely.

DURING THE PROCEDURE, A SPECIALIST USES A SMALL CAMERA CALLED A FETOSCOPE TO FIND THE BLOOD VESSELS SHARED BY THE TWIN FETUSES. A LASER IS THEN USED TO CLOSE THE VESSELS, ELIMINATING THE SHARING OF FLUIDS.

Recent studies have confirmed that laser surgery for TTTS offers better outcomes for both fetuses and a lower risk of preterm birth than serial amnioreductions.

Kelly first learned she had TTTS during a 20-week ultrasound at a WashU Medicine maternal-fetal medicine and ultrasound clinic in Carbondale, Illinois, where she was receiving care via telemedicine. (At WashU Medicine clinics in Illinois, clinical services are provided by WashU Physicians in Illinois, Inc.) After that diagnosis, Dr. Bligard says, “Kelly came to St. Louis for the laser procedure. We were able to do the majority of her follow-up care virtually,” so that she didn’t have to make repeated trips to St. Louis. Kelly delivered her twins in January 2025 at Barnes-Jewish Hospital at 34 weeks because one of the babies was measuring smaller than expected. The girls, Khloe and Karlee, spent some time in the newborn intensive care unit (NICU) at St. Louis Children’s Hospital, then went home. They continue to thrive.

“I cared for Kelly throughout her pregnancy, which was a great experience,” Dr. Bligard says. “I was also the lucky one to help her through delivery—truly making this a full-circle pregnancy for us as patient and doctor. I was very happy that I got to be there to finally meet her daughters outside the uterus.”

Helping babies survive and thrive

The Fetal Care Center at Barnes-Jewish Hospital, St. Louis Children’s Hospital, and WashU Medicine Physicians treats patients with TTTS from around the region, receiving referrals from Missouri and seven surrounding states, Dr. Bligard says, noting that she also is training other specialists to perform the procedure. When women with TTTS are diagnosed at Barnes-Jewish Hospital—or receive a diagnosis elsewhere and are referred for treatment—they are evaluated and then monitored to watch for the syndrome’s progression. When surgery is necessary, it is scheduled quickly.

KATHY BLIGARD, MD, MA, MATERNAL-FETAL MEDICINE SPECIALIST, REVIEWS AN ULTRASOUND IMAGE OF A FETUS.

After the procedure, about half of women with TTTS return to the care of their primary obstetricians and can deliver at their home hospitals if they were referred for care, says Jagruti Anadkat, MD, WashU Medicine neonatologist at St. Louis Children’s Hospital and co-director of the Fetal Care Center. Other patients are monitored through Barnes-Jewish Hospital and deliver their babies there. “Some women are able to make it to 34 or 36 weeks of pregnancy, as close to term as possible, and the outcomes are excellent,” Dr. Anadkat says. “Survival and outcomes depend on the gestational age of the babies. Those born significantly preterm may experience more serious medical complications.”

The complications caused by significant preterm birth can include developmental delays, an increased risk of lung disease, intraventricular hemorrhage (bleeding in the brain), visual impairment, and infections. When babies are born early, Dr. Anadkat says, “there’s still a lot of development that should be happening inside the womb that will now have to occur outside.” When such complications are present in premature newborns, they are cared for in a NICU, where specialists can address an infant’s health problems while supporting new parents. The care team working in the NICU at St. Louis Children’s Hospital and WashU Medicine includes neonatologists, nurse practitioners, bedside nurses, therapists, pharmacists, and nutritionists.

Ultimately, for the patients who have TTTS, the treatment available at Barnes-Jewish Hospital and St. Louis Children’s Hospital means that “hopefully, these women can go on to have a healthy pregnancy and deliver as close to term as possible, based on their health and the health of the twin fetuses,” Dr. Anadkat says. “That is always our goal.”