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TTTS Explanation

TTTS (As We Understand It)

            The text below is from a message I sent out explaining TTTS to our friends and family.  It is a layperson's explanation of the syndrome and may contain some inaccuracies, but I hope it does a fair job of providing the basics.

20 February, 2002

I had a request from someone to explain what's going on with our twins, so I thought I would share what I've learned with everyone, in the hopes that it will help someone else. You can find lots of information at, and is good, too.

Our daughters have a condition known as Twin-Twin Transfusion Syndrome (TTTS). This is a condition that occurs in about 10-15% of identical twin sets. Without treatment, the condition is almost always fatal for both babies. In TTTS, the babies are connected to one another by blood vessels in the placenta and one baby ends up providing blood for the other baby. The doctors aren't sure why this happens, but they think it has something to do with unequal sharing of the placenta through a disproportionate development of connecting blood vessels.

As the condition progresses, the recipient baby becomes larger and builds up an excess of fluid, due to the extra blood supply. Initially, this extra fluid shows up in the amniotic sac. This extra fluid condition is called polyhydramniose. Later, if uncorrected, the problem can lead to a condition called hydrops, in which the fluid begins to build in the recipient baby's body. The doctors have likened this situation to an adult in heart failure, because the baby is processing so much fluid that she can't keep up. Her heart gets over worked and the fluid builds up in the belly and sometimes in the head.  In the more serious stages of hydrops, the tissue (i.e. the skin) itself becomes full of fluid, as well.

The donor baby, in the meantime, is not producing enough fluid (called oligohydramnios). Her amniotic sac is not full enough, meaning she doesn't have enough cushion. Passing all of her blood to her sister leaves her in a kind of anemic state, which can cause problems for her heart as well.  Additionally, her kidneys usually begin to fail in the later stages, making the chances for her recovery slim.

The course of treatment for this condition began (for us) with the removal of a large amount of fluid from the polyhydramnios baby's sac. In our case, the night we found out, the doctor's removed 2.3 liters of fluid. Sometimes, that alone is enough to correct the problem, although the doctors aren't sure why. Occasionally, they will be able to do a few of the procedures (called serial amniocentesis) over the course of the pregnancy to get the babies to the point where they can be delivered safely. Unfortunately, that didn't work for us.

So, we've moved on to the next phase. The procedure is called Laser Photocoagulation of the Communicating Vessels (L-PCV). This is a surgical procedure in which the doctors make a tiny incision in the uterus, though which they thread an endoscope with a laser. They use the endoscope and a sonogram together to identify which blood vessels connect the two babies and use the laser to close some or all of those blood vessels. Closing off all the communicating vessels will eliminate the condition completely, and will also prevent any damage to one baby if for some reason the other baby doesn't make it. The doctors have told us that there is some risk in closing off all the connections, though.

Apparently, the smaller (donor) baby may not have a fair share of the placenta. Even though she is giving most of her blood to the other baby, she is also getting some blood back from her sister. Closing off all the connections may be bad for her if she grows to a point at which her share of the placenta is no longer sufficient to provide what she needs. By leaving open some of the channels, there is a stronger chance that she will have enough blood to develop enough that she will be able to survive. This is, of course, provided that the other baby does not pass away.

In the end of it all, the decision on how much of the communication to close off is based on how likely each of the babies is to survive. In our case, the doctors have done numerous sonograms and an MRI and determined that both babies are equally likely to survive, so we decided to do our best to save both of them (i.e., closing off most, but not all, of the blood vessels). The doctors are very concerned about this, due to the late stage of the syndrome, but they think there is some chance it might work, so they were willing to do it.

Should one or both babies survive, the long-term risks are mostly due to things like heart problems for the hydropic baby and cerebral palsy in either baby. The MRI's have indicated no definite signs of future problems, but there is always a chance.

I guess that's about it for my explanation. My intent here is not to scare anyone. This is a very rare condition and occurs only in sets of identical twins. The doctors at the UC San Francisco Medical Center have been fantastic, and I hear that the Florida Institute (at is great, too. Doctors are learning more and more about this syndrome every day, and with every case they treat.

If you have any other questions, please feel free to ask. Since I started writing this explanation, Helen has gone through the surgery, which the doctors say they think was successful, although we won't know with any certainty for some time.


In reality, the surgery was not entirely successful for us.  Two weeks after the surgery, the doctors discovered that the condition had actually "inverted."  I would say "reversed" but that usually refers to correcting the syndrome.  What happened, instead, was that the donor became a recipient and vice versa.  The doctors have theorized that this inversion happened because there was a blood vessel connecting the twins...a blood vessel that they could not see.

While TTTS is very rare to begin with, this was something the doctors had never seen at all before.  We continued to battle the syndrome for three more weeks using two amnio reduction treatments before the doctors decided it was time for the babies to be delivered.  The surgery at least seemed to slow progression of the syndrome, enabling us to fend off the worst effects with only two amnio reductions required before the babies reached the crucial 28-week mark.  For that, we are very grateful.

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