Procedures / active intervention in twin to twin syndrome.

There are 4 procedures which have been known to have role in the management of TTTS. The procedures include: 1) serial amniotic reduction 2) microseptostomy 3) selective fetal laser photocoagulation and 4) fetal cord occlusion / coagulation.

Amnioreduction

Amnioreduction is a procedure whereby a large volume of amniotic fluid is removed from the amniotic sac by amniocentesis procedure. A needle is introduced into the amniotic sac percutaneously through the abdomen into the amniotic sac of the recipient twin who develops polyhydramnios. The aim of amnioreduction in TTTS is to control polyhydramnios in hope of prolonging the pregnancy to reduce the risk of extreme prematurity. In addition to that, amnioreduction improves utero-placental blood flow, most likely by reducing intrauterine pressure. However, the procedure doesn’t treat the cause of the disease. The effect of amnioreduction is only temporary and the polyhydramnios may develop again as the disease progress. In order to be effective, the procedure need to be done repeatedly - ‘serial amnioreduction’. Since it is an invasive procedure, it poses risk of infection towards the pregnancy. The risk of intrauterine infection is increase with the number of repeated invasive procedure done.

amnioreduction done by amniocentesis

Microseptostomy

It is done by creating a small hole on the intertwine membrane. Similar to amnioreduction, the aim is to control polyhydramnios by amniotic fluid dynamic equalization between both amniotic sac of the recipient and donor twin. Unlike amnioreduction, this procedure doesn’t need to be repeated. Therefore, the risk of intrauterine infection is lowered compared to serial amnioreduction. However,there is risk of the hole become larger. If the hole get larger, instead of only the amniotic fluid able to cross the septostomy, the other structure, for example the cord, may as well cross the septostomy and this increase the risk of cord entanglement. 

microseptostomy

Fetal laser coagulation

This is the 1st procedure aims to treat the cause of the disease. Fetal laser coagulation therapy is a procedure whereby blood vessels on the intertwine membrane are occluded by laser therapy, thus arrests the shunting of blood from donor to recipient and stop the transfer of potential vasoactive mediators. Initially, the procedure include coagulation of all vessels on the intertwine membrane, including the normal vessels. This may lead to acute placental insufficiency since the normal vessels that carry nutrient and blood supply are also coagulated. After that, the procedure has been improved to selective fetal laser coagulation, whereby only the vessels that lead to unbalanced transfusion are occluded. This procedure considered as the most superior therapy for TTTS, however, it only available in selected institution and requires intensive training. Besides, in cases of the affected vessels lies deep in the membrane, it might not be detected thus fetal laser coagulation could not be done. 

fetal laser coagulation

Fetal cord occlusion

This procedure sacrifices one twin to save the other twin. It is the final resort for cases which there is already demise or imminent demise of one of the twin. It doesn’t only stop the progression of the syndrome, but also prolonged the gestation and maximize the outcome of the other twin.

fetal cord occlusion

Quintero staging system - twin to twin transfusion syndrome

Stage	Parameter	Criteria
1	MVP of amniotic fluid	MVP<2cm in donor and MVP>8cm in recipient
2	Fetal bladder	Fetal bladder in donor twin is not visualized over 60min observation
3	Doppler waveforms:	At least one of these 3 abnormalities:
	a-umbilical artery	Absent or reversed diastolic flow.
	b-ductus venosus	Reversed a-wave flow.
	c-umbilical vein	Pulsatile umbilical vein flow.
4	Fetal hydrops	Hydrops in one or both twins
5	Fetal cardiac activity	Absent cardiac activity – fetal demise in one or both twins.

Quintero system classified the disease into 5 stages based on the ultrasound findings. 5 parameters are assessed to stage the disease. The parameters include: 1) maximum vertical pocket (MVP) of amniotic fluid, 2) fetal bladder, 3)Dopplers abnormalities of the umbilical artery or ductus venosus, or umbilical vein, 4)fetal hydrops and 5)fetal cardiac activity.

Stage 1 disease occurs when the is only discordance in the amniotic fluid volume, the 1st criteria, which is detected by comparing the measurement of the maximum vertical pocket of the amniotic fluid in each amniotic sac of the donor twin and the recipient twin, with the absence of the other 4 criteria. When maximum vertical pocket of the amniotic fluid in donor sac less than 2cm and maximum vertical pocket of the amniotic fluid in recipient sac is more than 8cm, the disease is at least at stage 1. 

The presence of 2nd criteria that is non-visualization of donor twin bladder indicates at least stage 2. The disease is at least stage 3 when there is presence of the 3rd criteria that is the presence of any of these dopplers abnormalities: 1) absent or reversed diastolic flow of the umbilical artery, 2) reversed of a-wave flow of the ductus venosus or 3)pulsatile flow of the umbilical vein. Fetal hydrops (4th criteria) indicates at least stage 4 and when there is fetal demise (5th criteria) the disease already at stage 5.

-Maximum vertical pocket measurement-

-umbilical artery, ductus venosus and umbilical vein shown-

hydrops - ascites, pleural effusion and scalp edema shown-

Twins delivery, with one twin 3 times larger than the other one

Byron and Lincoln Ryman was born in March 2007. Their parents, Todd and Nicole Ryman, have been trying to have kids for so long, and finally Mrs Ryman got pregnant through in vitro fertilization (IVF), and she got a twin pregnancy.

Later on, the doctor noticed that there were some problems with her pregnancy. It was discovered that one of the twins was significantly smaller than the other one. The twins developed twin to twin transfusion syndrome, which may occurs only to some fetuses who shared the same placenta (monochorionic twins). The unbalanced transfusion between the babies cause Bryon to get hyper perfused while Lincoln was getting hypo perfused.

The parents were given an option to terminate Lincoln, the smaller baby, in hopes of saving Bryon. However, they didn’t agree. “I wanted to have 2 babies not one”, said Mrs Ryman.

During the pregnancy she was having weekly scans and she said the doctors would ‘write Lincoln off’ and told her to ‘be prepared to not see a heartbeat next week’.

In March 2007, she was induced at 29 weeks of gestation after the doctor discovered that Bryon had stop growing, and delivery of the babies seems to be the best option. The babies were born 11 weeks premature. Bryon, the firstborn is 3 times larger than his little brother, Lincoln. Bryon birth weight was 1.54kg while Lincoln was 530g only.

Born prematurely, both babies had been struggles to survive those critical periods with all the complication of premature birth. Initially the parents thought that they will have two boys with multiple health issues. In the beginning they had suffered from breathing problems, heart condition, and Lincoln had to take his food through feeding tube until the age of two. However, as miraculous as they are, these boys condition improved progressively and are doing very well.

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Twin-to-twin transfusion syndrome

Twin-to twin transfusion syndrome (TTTS) may occur only in twins who shared placenta (monochorionic twins) since they are connected by some the blood vessels in the placenta they shared. It is normal for monochorionic twins to exchange some blood during gestation and this exchange is usually balanced, means that at one moment the 1st twin will act as the blood donor while the 2nd is the recipient, and at the next moment the 2nd twin will act as the donor while the 1st become recipient.

Twin-to twin transfusion syndrome (TTTS) occurs when the exchange is unbalanced, where one of the twins always donates blood to the other. Twin-to twin transfusion syndrome (TTTS) not only compromises the donor twin, but also the recipient twin. Because there is less blood goes to the donor and more blood goes to the recipient, the donor become volume depletion and the recipient become volume overload.

With lees volume, the donor unable to produce enough amniotic fluid thus develops oligohydramnios. He also doesn’t get enough nutrients to grow and shows signs of intrauterine growth restriction.

Meanwhile, the recipient, who receives excessive volume, will develop polyhydramnios due to the excessive fluid. The recipient also tends to swell and develop heart failure (hydrops), due to the volume overload.

The risk and severity of the condition vary, depends on when is the onset occurs. If it starts later in gestation, the risks are usually minimal, and if there is complication occurs there is an option to deliver the baby earlier when they are mature enough to survive outside the womb. However, if the condition occurs earlier, before the babies mature enough to survive outside the womb, then there are not many options left and the risk is greater. 

Twin – donor	Twin – recipient
Hypovolemia	Hypervolemia
Oliguria / anuria	Polyuria
Oligohydramnios	Polyhydramnios
May develops hydrops due to anemia and high-output heart failure	May develops hydrops due to hypervolemia
Hypotension	Hypertension, hypertrophic cardiomegaly, disseminated intravascular coagulation