Twin to Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome (TTTS) is a rare condition of pregnancy that affects identical twins and other multiple pregnancies when two or more fetuses share a placenta. Before we dive into this complex and interesting topic, let’s review a few key basics and terms:

• Chorion – The outer membrane that aids in the formation of the placenta.
• Amnion – The inner membrane that covers the fetus.
• Monochorionic – When multiple fetuses share a placenta (ex: monochorionic twins). How placental circulation is dispersed between the two twins can vary from one pregnancy to another. When one twin is given more placental circulation, this can impact fetal growth and development. Complications are more likely to occur in monochorionic pregnancies. Monochorionic twins are always identical.
• Dichorionic – The placenta is not shared (though later in pregnancy the two placentas can fuse and appear to be one). Dichorionic twins can be identical or fraternal twins.
• Monoamniotic – A single yolk sac shared by more than one fetus (ex: monoamniotic twins).
• Diamniotic – Each twin has a separate yolk sac.
• Monozygotic – Twins derived from a single egg and single sperm (also called “identical twins”). About one third of monozygotic twins have two placentas and about two thirds share a placenta.
• Dizygotic – Twins derived from two eggs and two sperm (also called “fraternal twins”). Each fetus has its own placenta and own sac.

Also, there are three types of twin pregnancies: 

1. Dichorionic-diamniotic: No shared placenta, no shared sac. The twins can be fraternal or identical (you may hear this referred to as “di-di”).
2. Monochorionic-diamniotic: Shared placenta, separate sacs. The twins are identical.
3. Monochorionic-monoamniotic: Shared placenta, shared sac. The twins are  identical. Note this is the rarest type and highest risk multiple pregnancy.

Pathophysiology of TTTS

When the placenta is not divided evenly between monochorionic twins, the one with the most blood flow from the placenta receives more nutrients and oxygen. The condition is associated with the presence of vascular anastomoses deep in the placenta which leads to altered blood flow. Anastomoses can be artery to vein (AV), vein to vein (VV) and artery to artery (AA). 

Artery-to-vein anastomoses can lead to more blood flowing to one fetus. When this occurs, the donor twin experiences reduced blood flow, which leads to dehydration and less amniotic fluid. This triggers the RAAS pathway in the donor twin which results in oliguria and oligohydramnios. 

Conversely, the recipient twin gets increased blood flow, more amniotic fluid and even hypertension. With hypervolemia, there’s more cardiac stretch, increased ANP and BNP, the RAAS pathway is inhibited, which leads to polyuria and polyhydramnios.

The condition usually develops between weeks 16-26 gestation and is evaluated using the Quintero staging system. 

• Stage 1: Blood flow is abnormal, resulting in one twin receiving more than the other, but the bladder of the donor twin is visible.
• Stage 2: The bladder of the donor twin is no longer visible, but the Doppler assessment is not critically abnormal.
• Stage 3: Critically abnormal Doppler waveforms are present. This could be an absence of blood flow through the umbilical artery at the end of the cardiac cycle, pulsatile flow in the umbilical vein, or there could be no flow or backward flow in the ductus venosus (a vein that runs through the liver).
• Stage 4: Critically abnormal Doppler waveforms are present and the recipient shows sense of fluid overload such as ascites, pericardial effusion, pleural effusion, scalp edema or fetal hydrops.
• Stage 5: Death of one or both twins.

Complications of TTTS

Twin-to-twin transfusion syndrome has a 80-90% risk of perinatal mortality if left untreated. With treatment, the survival rate for both twins is 50%, and the survival rate for one twin is up to 70%.

Additionally, there are short and long-term neurological complications in about three to fifteen percent of surviving children. This can include cerebral palsy, cerebral injury, blindness, deafness and neurodevelopmental impairment (NDI).

Potential complications for the donor twin include: 

• Small or absent bladder
• Oligohydramnios
• Growth restriction
• Absent end diastolic flow in the umbilical artery
• Vascular hypertrophy, which can lead to heart failure and arrhythmias

Potential complications for the recipient twin include: 

• Cardiomegaly and heart failure
• Enlarged bladder
• Polyhydramnios
• Fetal ascites (abnormal fluid collection in the peritoneal cavity) and hydrops fetalis (an abnormal collection of fluid in two or more body cavities)
• Diastolic dysfunction
• Atrioventricular valve insufficiency
• Pulmonary stenosis or atresia

Potential complications for mothers include:

• Shortened cervix
• Premature rupture of membranes
• Preterm labor
• Mirroring syndrome – a rare development of maternal edema in the presence of hydrops fetalis (also called “fetal hydrops”)
• Increased prevalence of anxiety, depression, post-traumatic stress, and other psychological issues

Now that you have a baseline understanding of TTTS, let’s dive into the nursing implications using the Straight A Nursing LATTE method.

L: How does the patient LOOK? What are the signs and symptoms of TTTS? 

Maternal signs and symptoms can include rapid weight gain, edema, sudden increase in fatigue, increased abdominal and back pressure, difficulty sleeping, increased uterine size and preterm contractions. 

Ultrasound shows polyhydramnios in the recipient sac, oligohydramnios in the donor sac, discordant bladder sizes, and one fetus larger than the other.

At birth, the donor infant is typically smaller, pale and anemic while the recipient infant is larger, red and has hypertension. When the twins are of varying sizes, this is called “discordant” twins.

A: How do you ASSESS the patient?

Nursing assessments are mainly geared toward fetal monitoring as well as some key maternal assessments: 

• Assess for maternal comfort – pain from contractions, increased pressure on the back or abdomen, difficulty breathing due to increased uterine size and pressure
• Assess for cervical dilation and amniotic fluid leakage 
• Monitor CBC, CRP and ESR for signs of infection (especially after intervention)
• Assess pH of any leaked fluids to determine if they are amniotic fluid
• Monitor for signs of preeclampsia, which can occur in cases of maternal mirror syndrome. Watch for hypertension, vomiting, proteinuria, and increased edema (including pulmonary edema)
• Monitor for signs of infection, including temperature, elevated heart rate and abnormal labs
• Assess for any psychosocial needs such as social worker, spiritual care, community support and coping techniques

T: What TESTS will be conducted?

• Screening ultrasounds are conducted every two weeks in monochorionic multiple pregnancies starting at 16 weeks. Key things the MD is looking for are amniotic fluid imbalances (oligohydramnios and polyhydramnios) and discordant fetal growth.
• Doppler studies assess placental anastomoses as well the vessels evaluated in Quinterno staging (ductus venosus, umbilical artery, and umbilical vein)
• Fetal echocardiogram may be conducted to determine the severity of heart failure in the recipient twin.
• Fetal blood sampling to assess for fetal anemia.
• After the birth, the twin(s) will undergo routine newborn assessments and be evaluated for any specific complication the child may have. 

T: What TREATMENTS will be provided?

Treatments for TTTS will vary depending on the stage. 

Stage 1: Invasive treatment may not be needed if there are no symptoms and adequate cervical length is present. The twins will be monitored closely, which includes: 

• Weekly assessment of amniotic fluid
• Fetal growth measurements every three to four weeks
• Doppler blood flow studies are added at 16 weeks
• Starting at 30 weeks, biophysical profile assessment is conducted weekly
• Scheduled delivery at 34 to 37 weeks gestation in the absence of complications that may necessitate earlier delivery

Over 75% of those diagnosed in stage 1 may stay stable without invasive procedures. 

In cases of Stage 1 TTTS where the mother is symptomatic, having preterm contractions, experiencing respiratory difficulty or has a short cervix due to polyhydramnios, the treatment is fetoscopic laser ablation (also called fetal laser photocoagulation). In some cases amnioreduction may be utilized to relieve pressure in the uterus and relieve the maternal symptoms.

Stage 2, 3 and 4: The intervention for TTTS is fetal laser photocoagulation of the placental anastomoses between 16 and 26 weeks (possibly beyond at some centers and studies are ongoing in this area). After 26 weeks, amnioreduction may be utilized as laser photocoagulation is more difficult at this time.

Stage 5: When one twin dies the other remains at risk for neurological impairment and death. 

The surviving fetus will undergo additional testing including Doppler blood flow studies of the middle cerebral artery, fetal blood sampling (to assess for anemia), ultrasound examination every three to four weeks (to monitor development) and MRI (to detect intracranial injury).

In cases where the surviving twin has anemia, an in utero blood transfusion may be utilized.

What is fetal laser photocoagulation?

In this procedure, a laser is inserted through a thin tube and guided into the uterus where it is used to ablate blood vessels of the placenta. The goal is to eliminate imbalanced blood flow and restore volume status between the fetuses. It is usually conducted as an outpatient procedure using local anesthesia. In cases where the fetus is beyond 24 weeks gestation, corticosteroids are administered to promote lung maturity in case of preterm birth.

In addition to preterm birth, other complications of this procedure include PROM, intraamniotic bleeding, inter-twin membrane rupture, TAPS (a condition where the donor has anemia and the recipient has polycythemia), and fetal demise.

Two other treatments for TTTS

Other treatments for TTTS include amniotic septostomy and selective reduction. 

Amniotic septostomy is a procedure where the intertwin membrane is perforated to allow for equalization of amniotic fluid volume. A potential serious complication of this procedure is the accidental creation of too large an opening, leading to umbilical cord entanglement. 

Selective reduction may be considered in cases where both fetuses are at risk and one has significant complications with a low chance of survival.

E: How do you EDUCATE the patient/family about TTTS?

Parents experiencing TTTS will need a lot of education about prognoses, treatments, and long-term complications. In addition to providing the appropriate education about assessments and interventions, other things to teach the patient are: 

• Delivery is recommended between 34 and 37 weeks, but depends on severity and any complications that are present
• The incidence of preterm birth is high and the infant(s) will likely need to spend some time in the NICU while they continue to grow
• Ensure the mother and her partner understand the signs of preterm labor and when to seek medical attention. These can include regular contractions that increase in frequency and intensity, a change in vaginal discharge, a constant backache, pelvic pressure, and PROM.
• Educate the mother on the importance of attending all prenatal appointments (there will be many).
• Help parents find resources and community support as needed.
• Women with multiple pregnancies are advised to see their provider if they gain more than 7 pounds in one week, have a sudden increase in fatigue, have a sudden increase in abdominal pressure or lower back pressure.
• Encourage the patient to add additional calories/protein throughout the day to support multiple fetuses.

You can review twin-to-twin transfusion syndrome again while you’re on the go in episode 280 of the Straight A Nursing podcast. Tune in wherever you get your podcast fix, or straight from the website here.

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