Selected Podcast

Fetal Surgery for Twin-to-Twin Transfusion Syndrome

Twin-twin transfusion syndrome (TTTS) is a rare, serious condition that can occur in pregnancies when identical twins share a placenta. Abnormal blood vessel connections form in the placenta and allow blood to flow unevenly between the babies. One twin − called the donor – becomes dehydrated; and the other − called the recipient − develops high blood pressure and produces too much urine and over fills the amniotic sac.

Without treatment, this condition can be fatal for both twins. Dr. Bebbington, a leading fetal interventionist with 15 years of experience in open fetal surgery and fetoscopic-based interventions, joins the show to discuss twin-to-twin transfusion syndrome, and why fetal surgery is sometimes necessary to save one or both babies.
Fetal Surgery for Twin-to-Twin Transfusion Syndrome
Featured Speaker:
Michael Bebbington, MD
Michael Bebbington, MD is a Washington University maternal fetal medicine physician, surgeon and director of the Fetal Care Center at St. Louis Children's Hospital.



Transcription:

Melanie Cole (Host): Welcome, today we’re talking about fetal surgery for twin to twin transfusion syndrome, and my guest is Dr. Michael Bebbington. He’s a Washington University Maternal Fetal Medicine physician, surgeon, and the Director of the Fetal Care Center at St. Louis Children’s Hospital. Dr. Bebbington, I’m so glad to have you with us today because this is something I actually have not done a show on, tell us what is twin to twin transfusion syndrome.

Dr. Michael Bebbington (Guest): So twin to twin transfusion syndrome, or it’s probably easier to call it TTTS is a condition that develops in a very certain type of twin gestation where the twins are identical and they share one placenta. Each of the fetuses have blood vessels that project out from where the cord inserts and in this particular type of placenta, there are blood vessel connections within the placenta that allow blood to flow between the two fetuses, and this is a normal physiologic event, as long as the amount of blood that is going back and forth is normal or equal, then the world is a happy place, but if that blood flow becomes unequal and there’s more going in one direction than in the other, then that’s where we develop twin to twin transfusion syndrome.

Host: Wow, that’s fascinating. So tell us how is it diagnosed and evaluated, and is it something that once you’ve diagnosed it, you’re staging it so that you can see what treatment options are available?

Dr. Bebbington: So the commonest way for a diagnosis is by ultrasound. What’s unfortunate is that we don’t have any good strategies for predicting which monochorionic twin pregnancies will develop twin to twin transfusion syndrome. So we know about 15% of monochorionic twins will have that, but we can’t easily pick out which ones are most likely to develop it. So the only strategy that we have is regular ultrasound surveillance. So typically from 16 weeks on, moms with monochorionic twin pregnancies should have an ultrasound evaluation to look for any early signs of twin to twin transfusion syndrome. Typically that’s differences in the amount of fluid around each of the twins. The one twin that is giving blood away, or as it’s called the donor, starts to develop a decrease in the amount of amniotic fluid. The other twin that’s receiving the extra blood, or the recipient, develops increased amounts of amniotic fluid, and that’s usually that’s sort of the ultrasound criteria for defining the earliest stage of twin to twin transfusion syndrome.

Host: So how does it affect each twin and how does it affect the pregnancy if at all?

Dr. Bebbington: So the twin that is donating blood basically becomes volume depleted and that fetus responds to the blood volume depletion, much the same way that any of us would. If we suffered a blood volume loss, in that they centralize their circulation, and for a fetus, the most important parts to be circulated or to have blood flow is your heart and your head – your brain. So they basically shunt more blood into the central part of their bodies, and decrease the amount of blood that perfusing the other parts of the bodies. Where we see that most is in how much blood is going to the kidneys because the kidneys filter the blood, make urine, babies pee and that’s what gives them amniotic fluid. So as that fetus becomes more and more volume deplete, the amount of amniotic fluid surrounding that baby decreases, and when it gets to the stage 2 the volume depletion is so rapid that any urine that’s being made is being reabsorbed into the body and so none of it makes it to the bladder. The bladder becomes not visible, and the amount of amniotic fluid just continues to decrease and decrease. For the co-twin, the recipient twin, they have the opposite problem. They’ve got too much blood, and so they compensate by increasing renal perfusion and increasing the amount of urine and thus the amount of amniotic fluid starts to go up, and sort of the more serious cases, that amniotic fluid can distend the uterus considerably making mom very uncomfortable and increasing risk for preterm labor and preterm rupture of the membranes. So in its untreated form, it’s a condition that is associated with very, very high perinatal morbidity and mortality, mortality rates up to 85%, all as a result of extreme prematurity.

Host: Wow, so are there treatment options? Tell us what they are and at what point might surgery be necessary?

Dr. Bebbington: So the best treatment option that we have right now is laser surgery and that’s a procedure where we put an endoscope through the maternal abdomen, through the wall of the uterus, into the sac of the recipient twin, into the extra fluid that’s there, gives us a good medium for visualization and surgery and essentially we map the placenta to find where the blood vessels from the two fetuses overlap in what’s called the vascular equator, and with the scope basically going from one side of the placenta to the other, we can identify where the connecting points are, and then we use an operative fetus scope that has a side port to put in a 600 micron laser fiber and go back and basically where ever there are connections between the circulations we use the laser energy to clot the blood and those connections and then the final step of the surgery, once you’ve clotted all the connecting points is basically to just take a laser and draw a line to connect the dots so to speak so that at the end of the procedure, the fetus are no longer transfusing blood back and forth and effectively separate the placenta into two parts, one for each fetus, and then we let mother nature correct the physiology gradually as the transfusion process is stopped, the fetuses can recover.

Host: What are some of the outcomes you’ve seen? What’s the outlook after this type of surgery?

Dr. Bebbington: So it can be very good in experienced hands. I said in its untreated form the perinatal mortality rate is about 85%, but in experienced hands with the surgery we can change that to about an 86% overall survival and about 72% to 74% survival of both fetuses, both twins.

Host: What about future pregnancies?

Dr. Bebbington: Future pregnancies are really unaffected as long as you don’t have another set of monochorionic twins. This is a clinical or an entity that is specific to monochorionic twins, and the surgery really doesn’t increase risks and other pregnancies for complications.

Host: This is so interesting Dr. Bebbington. So what else would a referring OB or pediatrician want to know about TTTS and the expertise of the Fetal Care Center?

Dr. Bebbington: So most of the referring doctors, the one message that I have is monochorionic twins need to be watched very closely and with ultrasound surveillance at least every 2 weeks and to refer to a fetal surgery center at the first sign of any discordance in the amount of amniotic fluid. One of the things that I appreciate from my referring docs is to have the patient sent early. Even if they don’t need surgery right away, what that gives me is an opportunity to sit with the family and explain what’s going on and what potential interventions we can offer when it gets to the point where an intervention is needed. So we get a chance to sit and discuss in a very calm scenario, rather than having somebody referred last minute whose babies are both very sick and need urgent surgery, where we don’t have that sort of luxury of time to have conversations.

Host: What a great point you just made for the reasoning behind early referral and how important that is. What can a referring physician expect from your team after referral in so far as communication with the physician and your team approach?

Dr. Bebbington: So one of the things we pride ourselves on is our referral – how we relate to our referring docs. So after I’ve seen a patient, typically we can get a phone call to the referring doc the same day or the next day to sort of outline what we’ve found and what the plan would be. I certainly, with all of the modern communications, have a number of my referring docs who say just text me and so we can send a HIPAA compliant text that gives the essence of what’s coming and all of my referring docs then get a follow up consultation letter that outlines in detail what we’ve discussed and what the options are.

Host: Do you have some final thoughts you’d like to share on fetal surgery for twin to twin transfusion syndrome?

Dr. Bebbington: Just that it’s game changing, and if you ever have a chance to talk to some of the families, we really have an opportunity to make a huge difference with early referral and with timely intervention with laser therapy, we can have a significant impact on pregnancy outcomes.

Host: Thank you so much Dr. Bebbington for coming on and sharing your incredible expertise, to describe this particular syndrome and the options available for treatment. To consult with a specialist or to learn more about services offered at St. Louis Children’s Hospital, call Children’s Direct Physician Access Line, at 1-800-678-HELP, that’s 1-800-678-4357 and that wraps up this episode of Radio Rounds with St. Louis Children’s Hospital. Please head on over to our website at stlouischildrens.org for more information and to get connected with one of our providers. If you as a provider found this podcast informative, please share on your social media and be sure to check out all of the other fascinating podcasts in our library. This is Melanie Cole.