Twin-to-Twin Transfusion Syndrome (TTTS)
Without medical intervention, TTTS results in fetal death in 60–100% of cases. Two main approaches are used to preserve the pregnancy:
- Serial amnioreductions. These prolong gestation, and in 30–60% of cases, at least one live infant is successfully delivered. However, this method does not protect against brain damage—neurological deficit occurs in 18–37% of surviving children.
- Endoscopic laser coagulation. This involves laser ablation («coagulation») of placental anastomotic vessels. This is a fundamentally more effective method: survival of at least one child reaches 70–80%, and the incidence of neurological complications drops to 5%.
Twin Reversed Arterial Perfusion Sequence
This is an extreme and most severe form of TTTS, which occurs exclusively in monochorionic placentation. The pathology develops due to umbilical artery-to-artery anastomoses, where one twin literally grows at the expense of the other's resources.
- Donor twin («pump»). Has no structural anomalies, but is forced to maintain hemodynamics for two. Without medical intervention, the prognosis is extremely unfavorable.
- Recipient twin («parasite»). Always has multiple lethal malformations: absence of a head (acrania), heart (acardia), or severe underdevelopment thereof.
Surgical intrauterine treatment is associated with up to 50% mortality. To preserve the life of the healthy donor twin, feticide of the recipient is performed by ligating its umbilical cord.
Intrauterine Fetal Demise: Timing and Causes
Antenatal death of one of the twins can occur at any stage of gestation. In the first trimester, approximately 20% of cases involve the demise of one gestational sac. In the second trimester, the demised fetus mummifies, turning into a «fetus papyraceus» (fetus papyraceus).
In the third trimester, risks depend on the type of placentation. In monochorionic twins, demise occurs twice as often as in dichorionic twins.
Main causes of late demise:
- In monochorionic placentation: TTTS and selective fetal growth restriction (FGR).
- In dichorionic placentation: FGR and velamentous cord insertion.
Obstetric Management in Single-Twin Demise
The physician's action algorithm depends strictly on chorionicity and gestational age.
- Dichorionic twins. Expectant management is considered optimal. Pregnancy is continued under close monitoring.
- Monochorionic twins (viable gestational age). The death of one fetus causes a sharp redistribution of blood («hemorrhage») into its fetoplacental complex. The survivor develops severe arterial hypotension, leading to irreversible brain damage. The only way to save it is an emergency Cesarean section, which must be performed as quickly as possible.
- Monochorionic twins (pre-viability). Doctors focus on the peak systolic velocity in the middle cerebral artery (MCA) of the surviving fetus. If anemia is detected, intravascular blood transfusion is performed and pregnancy is prolonged. If there is no anemia, the pregnancy is maintained under strict dynamic surveillance.
Briefly: answers to topical questions
What are the stages of twin-to-twin transfusion syndrome according to the Quintero classification?
According to the Quintero classification, there are five stages of twin-to-twin transfusion syndrome, based on ultrasound findings and dopplerometry.
- Stage I — oligohydramnios in the donor twin and polyhydramnios in the recipient; visualization of the donor's bladder is preserved.
- Stage II — marked amniotic fluid discordance; the donor's urinary bladder is not visualized.
- Stage III — abnormal blood flow is detected in one or both fetuses (in the umbilical arteries, ductus venosus, or umbilical vein).
- Stage IV — development of fetal hydrops (ascites, pericardial effusion, pleural effusion, generalized edema).
- Stage V — demise of one or both fetuses.
What specific ultrasound criteria are used to diagnose twin-to-twin transfusion syndrome?
The following ultrasound and dopplerometric criteria are used to diagnose twin-to-twin transfusion syndrome:
- Amniotic fluid volume — oligohydramnios in the donor twin: maximum vertical pocket less than 2 cm; polyhydramnios in the recipient twin: maximum vertical pocket greater than 8 cm before 20 weeks and greater than 10 cm after 20 weeks.
- Bladder status — visualization of the donor's bladder corresponds to Stage I, absence of visualization corresponds to Stage II.
- Blood flow parameters — absent or reversed diastolic flow in the umbilical arteries, reversed A-wave in the ductus venosus, pulsatile waveform in the umbilical vein.
- Signs of hydrops — ascites, pericardial effusion, pleural effusion, subcutaneous edema of the head and trunk.
In which cases is selective feticide indicated in multiple gestation?
Selective feticide in multiple gestation is indicated in the following cases:
- Developmental anomalies — presence of severe congenital malformations in one of the fetuses.
- Chromosomal pathology — in discordance, when only one fetus is affected by the condition.
- Complicated TTTS — combination of the syndrome with selective growth restriction of one fetus with discordance greater than 40% (prior to 22 weeks).
- Severe TTTS — Stage IV of the syndrome in the absence of technical capability to perform laser coagulation.
- Twin reversed arterial perfusion sequence — feticide of the recipient twin is performed to preserve the life of the donor twin.
Basic rule of management in fetal demise: Dichorionic — Deliberate wait (expectant management), Monochorionic — Meet urgently (emergency Cesarean section at a viable gestational age).
Class and exam questions
What is the main advantage of laser coagulation over amnioreduction?
Laser coagulation eliminates vascular anastomoses, which reduces the risk of neurological disorders in children from 18–37% to 5% and increases the chances of live birth to 70–80%.
What is reverse arterial perfusion?
This is a specific complication of monochorionic twins in which the donor twin acts as a «pump» for the recipient twin. The recipient exhibits incompatible-with-life malformations (e.g., acardia or acrania).
How to save the donor fetus in reverse arterial perfusion?
The only solution is to perform feticide of the recipient twin by ligating its umbilical cord. However, even with this intrauterine intervention, mortality reaches 50%.
Why evaluate blood flow in the MCA in the early death of one monochorionic fetus?
This is necessary to diagnose anemia in the surviving twin. If present, the fetus requires an intravascular blood transfusion to successfully prolong pregnancy until a viable gestational age.
What else to study on this topic
- Mechanism of arterial hypotension development in the surviving fetus
- Technique of endoscopic laser coagulation of anastomoses
- Ultrasound diagnosis of acardia and acrania
- Selective fetal growth restriction: criteria and management
- Velamentous cord insertion in dichorionic twins
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