TTTS (Twin-to-Twin Transfusion syndrome) is a usually rare and a severe disease which develops in 5-10 percent of pregnant women expecting monochorionic twins. The condition develops because the two blood supplying vessels in the fused placentas are abnormally connected which results in unequal distribution of blood flow.
Epidemiology
Their occurrence in pregnancies ranges from 3-5 every 1000 pregnancies. About 75% of monozygotic twin can be described as monochorionic. TTTS is seen in 10-15 % of the monochorionic twin pregnancies.
Anatomy
Pathophysiology
Shared Placenta and Vascular Anastomoses
Monochorionic placentation:
In TTTS, both twins are connected by a single placenta anastomosis between both the fetal circulations i.e. blood vessels.
Types of anastomoses:
Arteriovenous (AV) anastomoses: TTTS is most critical when one baby possesses an artery that links with the second baby’s vein and the blood is shuttled from the first twin to the second twin.
Arterio-arterial (AA) and veno-venous (VV) anastomoses: These are compensating but probably will not be adequate to regain blood flow.
Imbalance in Blood Flow: The donor twin circulates blood through the AV anastomosis to the recipient twin most of the time.
Stunted growth (fetal growth retardation or intrauterine growth retardation: IUGR).
Risk of hypoxia and anemia.
Recipient twin:
Hypervolemia
Increased urine production
Cardiomegaly
Placental Dysfunction:
The abnormal vascular sharing compromises placental efficiency, further exacerbating growth and oxygen supply issues, particularly for the donor twin.
Etiology
Monochorionic Placenta and Vascular Anastomoses:
This condition occurs only in monochorionic twin pregnancies where the two babies share one placenta. In this placenta, there are blood vessels that interconnect the circulatory systems of the two fetuses.
Vascular anastomoses (connections between blood vessels) are critical in TTTS:
Arteriovenous (AV) anastomoses: Connect an artery of one twin to a vein of the other twin. These are unidirectional and are the main contributors to TTTS.
Arterioarterial (AA) and venovenous (VV) anastomoses: Bidirectional connections that can counterbalance AV flow but may be absent or insufficient in TTTS cases.
Imbalance in Blood Flow:
The blood flow abnormalities in TTTS results from the unequal distribution of placental vascular plexuses across the AV anastomoses leading to a chronic state of low blood flow to the recipient twin and high blood flow to the donor twin.
This leads to:
Donor twin: Loses more blood than it receives that leads to hypovolemia, anemia and low amniotic fluid levels (oligohydramnios).
Recipient twin: Receives excessive blood causing hypervolemia polycythemia and polyhdramnios (high levels of amniotic fluid).
Placental Contribution:
Unequal placental sharing: The area of the placenta that supports twin growth is shared, however, the donor twin usually gets less space than the other twin.
Abnormal placental development: This functional asymmetry may be amplified in TTTS’s placental architecture through fewer AA or VV anastomoses present for compensation.
Hormonal and Growth Factors:
Renin-angiotensin-aldosterone system (RAAS): Volume imbalance is exacerbated already that the donor twin exhibits hyperactivation as this warrants fluid retention in the recipient twin.
VEGF and other angiogenic factors may be responsible for the pathogenesis of TTTS and the progression of placental vascular pathology.
Genetics
Prognostic Factors
Presence of Hydrops Fetalis:
This condition either twin compromise the prognosis and raise the chance of fetal death and preterm birth.
Placental share: Unequal placental sharing worsens TTTS outcomes because it can exacerbate the severity of donor and recipient twin pathologies.
Abnormal Doppler Studies: Doppler changes, such as reversed flow in the umbilical artery or ductus venosus are suggestive for arterial cerebral insufficiency and are related to higher mortality and morbidity rates.
Clinical History
Age Group:
TTTS can develop at any time from early pregnancy or even during the second trimester, at approximately 16 to 18 weeks, or at a later stage of pregnancy, at about 26 to 28 weeks of pregnancy, although earlier or later depending on its severity and the placentation.
Physical Examination
Physical examination alone cannot definitively diagnose TTTS; ultrasound is essential. Findings may include:
Discordant growth between twins.
Polyhydramnios (excess fluid) in the recipient sac.
Oligohydramnios (low fluid) in the donor sac.
Absence of bladder filling in the donor twin, due to poor perfusion.
Age group
Associated comorbidity
Donor Twin:
Intrauterine Growth Restriction (IUGR)
Anemia
Oligohydramnios
Hypovolemia
Recipient Twin:
Polycythemia
Polyhydramnios
Cardiomegaly and Heart Failure
Hydrops Fetalis
Associated activity
Acuity of presentation
Gradual Onset:
Essentially discovered during the screening process, with the routine, ultrasound being the most common choice.
Signs like discordant amniotic fluid levels, growth restriction, or abnormal Doppler findings may develop over days to weeks.
Allows for some time to plan interventions, like serial ultrasounds or fetoscopic laser ablation.
Acute Onset:
Rare but critical.
Some can be caused by sudden dynamic placental blood vessel disorders like large arteriovenous shunting or placental abruption. Hence, exact assessment should be done at the earliest and necessary action should be taken because both twins are at high risk.
Differential Diagnoses
Selective Intrauterine Growth Restriction (sIUGR)
Monochorionic Monoamniotic Twin Pregnancy
Twin Anemia Polycythemia Sequence (TAPS)
Hydrops Fetalis
Laboratory Studies
Imaging Studies
Procedures
Histologic Findings
Staging
Treatment Paradigm
Close Monitoring and Diagnosis:
Ultrasound and Doppler Imaging: The first procedure before arriving at a TTTS diagnosis is comprehensive ultrasound scan and Doppler scan to assess the amniotic fluid levels and blood flow in both twins.
The findings of TTTS include polyhydramnios in the recipient twin, and oligohydramnios in the donor twin.
Stage Classification (Quintero Staging System): TTTS is further divided into five forms of stages I-V depending on the severity of the condition.
Evaluation and staging at the initial phase are important in recommending the most appropriate management of the condition.
Conservative Management:
Serial Monitoring: Treatments available for TTTS may include early intervention for cases where the condition is mild and the disease in its early stage and can be closely watched with obstetrical ultrasounds.
If the condition does not deteriorate, it may be managed and the pregnancy followed up as usual.
Invasive Interventions:
Amnioreduction (Stage I/II): Amniocentesis is used most in the reduction of the amount of amniotic fluid present with the recipient twin. This can ease the pressure and often relieves the symptoms of TTTS but does no cure the disease.
The best treatment for TTTS is fetoscopic laser surgery, whereby a tiny camera (fetoscope) is inserted into the uterus to give a direct view of the placenta before a laser is used to selectively ablate (destroy) the vessels in the shared placenta responsible for the flow of blood between the twins.
Amnioreduction: This involves aspiration of the excess fluid from the sac of the recipient twin through an intrauterine needle. It can relieve pressure and improves blood circulation; however, it doesn’t treat the underlying TTTS.
Selective Reduction: In some cases where one twin is severely compromised, the medical team may recommend selective reduction, which involves terminating the most affected twin to improve the chances of survival for the other.
Diagnosis is achieved by ultrasound, identifying unequal distribution of amniotic fluid, and abnormal flow characteristics. The care required is constant observation of the two fetuses, the amniotic fluid and their heart rates.
Conservative Management (for mild cases): In severe conditions observation and constant assessment of the condition may be needed. This may involve serial ultrasounds and dopplers to monitor the status of the condition of the mother and/or the baby.
Intrauterine Intervention:
Amnioreduction: Removal of excess amniotic fluid from the recipient’s sac to relieve pressure and improve blood flow.
Laser Therapy: Selective laser photocoagulation of the abnormally connected vessels in the placenta aids in correcting the blood flow which is the primary reason for TTTS.
The moderate to severe form of the disease is treated through selective laser photocoagulation.
Septostomy: A procedure where a hole is made in the dividing membrane between the fetuses to allow better fluid distribution.
Post-treatment
Monitoring: Post-intervention, assessment of uterine cavity, fetal heart rate tracking, and overall fetal status of both fetuses.
»
Home » CAD » Twin-to-Twin Transfusion Syndrome
Twin-to-Twin Transfusion Syndrome
Updated :
December 16, 2024
TTTS (Twin-to-Twin Transfusion syndrome) is a usually rare and a severe disease which develops in 5-10 percent of pregnant women expecting monochorionic twins. The condition develops because the two blood supplying vessels in the fused placentas are abnormally connected which results in unequal distribution of blood flow.
Their occurrence in pregnancies ranges from 3-5 every 1000 pregnancies. About 75% of monozygotic twin can be described as monochorionic. TTTS is seen in 10-15 % of the monochorionic twin pregnancies.
Shared Placenta and Vascular Anastomoses
Monochorionic placentation:
In TTTS, both twins are connected by a single placenta anastomosis between both the fetal circulations i.e. blood vessels.
Types of anastomoses:
Arteriovenous (AV) anastomoses: TTTS is most critical when one baby possesses an artery that links with the second baby’s vein and the blood is shuttled from the first twin to the second twin.
Arterio-arterial (AA) and veno-venous (VV) anastomoses: These are compensating but probably will not be adequate to regain blood flow.
Imbalance in Blood Flow: The donor twin circulates blood through the AV anastomosis to the recipient twin most of the time.
Stunted growth (fetal growth retardation or intrauterine growth retardation: IUGR).
Risk of hypoxia and anemia.
Recipient twin:
Hypervolemia
Increased urine production
Cardiomegaly
Placental Dysfunction:
The abnormal vascular sharing compromises placental efficiency, further exacerbating growth and oxygen supply issues, particularly for the donor twin.
Monochorionic Placenta and Vascular Anastomoses:
This condition occurs only in monochorionic twin pregnancies where the two babies share one placenta. In this placenta, there are blood vessels that interconnect the circulatory systems of the two fetuses.
Vascular anastomoses (connections between blood vessels) are critical in TTTS:
Arteriovenous (AV) anastomoses: Connect an artery of one twin to a vein of the other twin. These are unidirectional and are the main contributors to TTTS.
Arterioarterial (AA) and venovenous (VV) anastomoses: Bidirectional connections that can counterbalance AV flow but may be absent or insufficient in TTTS cases.
Imbalance in Blood Flow:
The blood flow abnormalities in TTTS results from the unequal distribution of placental vascular plexuses across the AV anastomoses leading to a chronic state of low blood flow to the recipient twin and high blood flow to the donor twin.
This leads to:
Donor twin: Loses more blood than it receives that leads to hypovolemia, anemia and low amniotic fluid levels (oligohydramnios).
Recipient twin: Receives excessive blood causing hypervolemia polycythemia and polyhdramnios (high levels of amniotic fluid).
Placental Contribution:
Unequal placental sharing: The area of the placenta that supports twin growth is shared, however, the donor twin usually gets less space than the other twin.
Abnormal placental development: This functional asymmetry may be amplified in TTTS’s placental architecture through fewer AA or VV anastomoses present for compensation.
Hormonal and Growth Factors:
Renin-angiotensin-aldosterone system (RAAS): Volume imbalance is exacerbated already that the donor twin exhibits hyperactivation as this warrants fluid retention in the recipient twin.
VEGF and other angiogenic factors may be responsible for the pathogenesis of TTTS and the progression of placental vascular pathology.
Presence of Hydrops Fetalis:
This condition either twin compromise the prognosis and raise the chance of fetal death and preterm birth.
Placental share: Unequal placental sharing worsens TTTS outcomes because it can exacerbate the severity of donor and recipient twin pathologies.
Abnormal Doppler Studies: Doppler changes, such as reversed flow in the umbilical artery or ductus venosus are suggestive for arterial cerebral insufficiency and are related to higher mortality and morbidity rates.
Age Group:
TTTS can develop at any time from early pregnancy or even during the second trimester, at approximately 16 to 18 weeks, or at a later stage of pregnancy, at about 26 to 28 weeks of pregnancy, although earlier or later depending on its severity and the placentation.
Physical examination alone cannot definitively diagnose TTTS; ultrasound is essential. Findings may include:
Discordant growth between twins.
Polyhydramnios (excess fluid) in the recipient sac.
Oligohydramnios (low fluid) in the donor sac.
Absence of bladder filling in the donor twin, due to poor perfusion.
Donor Twin:
Intrauterine Growth Restriction (IUGR)
Anemia
Oligohydramnios
Hypovolemia
Recipient Twin:
Polycythemia
Polyhydramnios
Cardiomegaly and Heart Failure
Hydrops Fetalis
Gradual Onset:
Essentially discovered during the screening process, with the routine, ultrasound being the most common choice.
Signs like discordant amniotic fluid levels, growth restriction, or abnormal Doppler findings may develop over days to weeks.
Allows for some time to plan interventions, like serial ultrasounds or fetoscopic laser ablation.
Acute Onset:
Rare but critical.
Some can be caused by sudden dynamic placental blood vessel disorders like large arteriovenous shunting or placental abruption. Hence, exact assessment should be done at the earliest and necessary action should be taken because both twins are at high risk.
Selective Intrauterine Growth Restriction (sIUGR)
Monochorionic Monoamniotic Twin Pregnancy
Twin Anemia Polycythemia Sequence (TAPS)
Hydrops Fetalis
Close Monitoring and Diagnosis:
Ultrasound and Doppler Imaging: The first procedure before arriving at a TTTS diagnosis is comprehensive ultrasound scan and Doppler scan to assess the amniotic fluid levels and blood flow in both twins.
The findings of TTTS include polyhydramnios in the recipient twin, and oligohydramnios in the donor twin.
Stage Classification (Quintero Staging System): TTTS is further divided into five forms of stages I-V depending on the severity of the condition.
Evaluation and staging at the initial phase are important in recommending the most appropriate management of the condition.
Conservative Management:
Serial Monitoring: Treatments available for TTTS may include early intervention for cases where the condition is mild and the disease in its early stage and can be closely watched with obstetrical ultrasounds.
If the condition does not deteriorate, it may be managed and the pregnancy followed up as usual.
Invasive Interventions:
Amnioreduction (Stage I/II): Amniocentesis is used most in the reduction of the amount of amniotic fluid present with the recipient twin. This can ease the pressure and often relieves the symptoms of TTTS but does no cure the disease.
OB/GYN and Women\'s Health
Laser Surgery (Laser Ablation):
The best treatment for TTTS is fetoscopic laser surgery, whereby a tiny camera (fetoscope) is inserted into the uterus to give a direct view of the placenta before a laser is used to selectively ablate (destroy) the vessels in the shared placenta responsible for the flow of blood between the twins.
Amnioreduction: This involves aspiration of the excess fluid from the sac of the recipient twin through an intrauterine needle. It can relieve pressure and improves blood circulation; however, it doesn’t treat the underlying TTTS.
Selective Reduction: In some cases where one twin is severely compromised, the medical team may recommend selective reduction, which involves terminating the most affected twin to improve the chances of survival for the other.
OB/GYN and Women\'s Health
Early Diagnosis and Monitoring:
Diagnosis is achieved by ultrasound, identifying unequal distribution of amniotic fluid, and abnormal flow characteristics. The care required is constant observation of the two fetuses, the amniotic fluid and their heart rates.
Conservative Management (for mild cases): In severe conditions observation and constant assessment of the condition may be needed. This may involve serial ultrasounds and dopplers to monitor the status of the condition of the mother and/or the baby.
Intrauterine Intervention:
Amnioreduction: Removal of excess amniotic fluid from the recipient’s sac to relieve pressure and improve blood flow.
Laser Therapy: Selective laser photocoagulation of the abnormally connected vessels in the placenta aids in correcting the blood flow which is the primary reason for TTTS.
The moderate to severe form of the disease is treated through selective laser photocoagulation.
Septostomy: A procedure where a hole is made in the dividing membrane between the fetuses to allow better fluid distribution.
Post-treatment
Monitoring: Post-intervention, assessment of uterine cavity, fetal heart rate tracking, and overall fetal status of both fetuses.
TTTS (Twin-to-Twin Transfusion syndrome) is a usually rare and a severe disease which develops in 5-10 percent of pregnant women expecting monochorionic twins. The condition develops because the two blood supplying vessels in the fused placentas are abnormally connected which results in unequal distribution of blood flow.
Their occurrence in pregnancies ranges from 3-5 every 1000 pregnancies. About 75% of monozygotic twin can be described as monochorionic. TTTS is seen in 10-15 % of the monochorionic twin pregnancies.
Shared Placenta and Vascular Anastomoses
Monochorionic placentation:
In TTTS, both twins are connected by a single placenta anastomosis between both the fetal circulations i.e. blood vessels.
Types of anastomoses:
Arteriovenous (AV) anastomoses: TTTS is most critical when one baby possesses an artery that links with the second baby’s vein and the blood is shuttled from the first twin to the second twin.
Arterio-arterial (AA) and veno-venous (VV) anastomoses: These are compensating but probably will not be adequate to regain blood flow.
Imbalance in Blood Flow: The donor twin circulates blood through the AV anastomosis to the recipient twin most of the time.
Stunted growth (fetal growth retardation or intrauterine growth retardation: IUGR).
Risk of hypoxia and anemia.
Recipient twin:
Hypervolemia
Increased urine production
Cardiomegaly
Placental Dysfunction:
The abnormal vascular sharing compromises placental efficiency, further exacerbating growth and oxygen supply issues, particularly for the donor twin.
Monochorionic Placenta and Vascular Anastomoses:
This condition occurs only in monochorionic twin pregnancies where the two babies share one placenta. In this placenta, there are blood vessels that interconnect the circulatory systems of the two fetuses.
Vascular anastomoses (connections between blood vessels) are critical in TTTS:
Arteriovenous (AV) anastomoses: Connect an artery of one twin to a vein of the other twin. These are unidirectional and are the main contributors to TTTS.
Arterioarterial (AA) and venovenous (VV) anastomoses: Bidirectional connections that can counterbalance AV flow but may be absent or insufficient in TTTS cases.
Imbalance in Blood Flow:
The blood flow abnormalities in TTTS results from the unequal distribution of placental vascular plexuses across the AV anastomoses leading to a chronic state of low blood flow to the recipient twin and high blood flow to the donor twin.
This leads to:
Donor twin: Loses more blood than it receives that leads to hypovolemia, anemia and low amniotic fluid levels (oligohydramnios).
Recipient twin: Receives excessive blood causing hypervolemia polycythemia and polyhdramnios (high levels of amniotic fluid).
Placental Contribution:
Unequal placental sharing: The area of the placenta that supports twin growth is shared, however, the donor twin usually gets less space than the other twin.
Abnormal placental development: This functional asymmetry may be amplified in TTTS’s placental architecture through fewer AA or VV anastomoses present for compensation.
Hormonal and Growth Factors:
Renin-angiotensin-aldosterone system (RAAS): Volume imbalance is exacerbated already that the donor twin exhibits hyperactivation as this warrants fluid retention in the recipient twin.
VEGF and other angiogenic factors may be responsible for the pathogenesis of TTTS and the progression of placental vascular pathology.
Presence of Hydrops Fetalis:
This condition either twin compromise the prognosis and raise the chance of fetal death and preterm birth.
Placental share: Unequal placental sharing worsens TTTS outcomes because it can exacerbate the severity of donor and recipient twin pathologies.
Abnormal Doppler Studies: Doppler changes, such as reversed flow in the umbilical artery or ductus venosus are suggestive for arterial cerebral insufficiency and are related to higher mortality and morbidity rates.
Age Group:
TTTS can develop at any time from early pregnancy or even during the second trimester, at approximately 16 to 18 weeks, or at a later stage of pregnancy, at about 26 to 28 weeks of pregnancy, although earlier or later depending on its severity and the placentation.
Physical examination alone cannot definitively diagnose TTTS; ultrasound is essential. Findings may include:
Discordant growth between twins.
Polyhydramnios (excess fluid) in the recipient sac.
Oligohydramnios (low fluid) in the donor sac.
Absence of bladder filling in the donor twin, due to poor perfusion.
Donor Twin:
Intrauterine Growth Restriction (IUGR)
Anemia
Oligohydramnios
Hypovolemia
Recipient Twin:
Polycythemia
Polyhydramnios
Cardiomegaly and Heart Failure
Hydrops Fetalis
Gradual Onset:
Essentially discovered during the screening process, with the routine, ultrasound being the most common choice.
Signs like discordant amniotic fluid levels, growth restriction, or abnormal Doppler findings may develop over days to weeks.
Allows for some time to plan interventions, like serial ultrasounds or fetoscopic laser ablation.
Acute Onset:
Rare but critical.
Some can be caused by sudden dynamic placental blood vessel disorders like large arteriovenous shunting or placental abruption. Hence, exact assessment should be done at the earliest and necessary action should be taken because both twins are at high risk.
Selective Intrauterine Growth Restriction (sIUGR)
Monochorionic Monoamniotic Twin Pregnancy
Twin Anemia Polycythemia Sequence (TAPS)
Hydrops Fetalis
Close Monitoring and Diagnosis:
Ultrasound and Doppler Imaging: The first procedure before arriving at a TTTS diagnosis is comprehensive ultrasound scan and Doppler scan to assess the amniotic fluid levels and blood flow in both twins.
The findings of TTTS include polyhydramnios in the recipient twin, and oligohydramnios in the donor twin.
Stage Classification (Quintero Staging System): TTTS is further divided into five forms of stages I-V depending on the severity of the condition.
Evaluation and staging at the initial phase are important in recommending the most appropriate management of the condition.
Conservative Management:
Serial Monitoring: Treatments available for TTTS may include early intervention for cases where the condition is mild and the disease in its early stage and can be closely watched with obstetrical ultrasounds.
If the condition does not deteriorate, it may be managed and the pregnancy followed up as usual.
Invasive Interventions:
Amnioreduction (Stage I/II): Amniocentesis is used most in the reduction of the amount of amniotic fluid present with the recipient twin. This can ease the pressure and often relieves the symptoms of TTTS but does no cure the disease.
OB/GYN and Women\'s Health
Laser Surgery (Laser Ablation):
The best treatment for TTTS is fetoscopic laser surgery, whereby a tiny camera (fetoscope) is inserted into the uterus to give a direct view of the placenta before a laser is used to selectively ablate (destroy) the vessels in the shared placenta responsible for the flow of blood between the twins.
Amnioreduction: This involves aspiration of the excess fluid from the sac of the recipient twin through an intrauterine needle. It can relieve pressure and improves blood circulation; however, it doesn’t treat the underlying TTTS.
Selective Reduction: In some cases where one twin is severely compromised, the medical team may recommend selective reduction, which involves terminating the most affected twin to improve the chances of survival for the other.
OB/GYN and Women\'s Health
Early Diagnosis and Monitoring:
Diagnosis is achieved by ultrasound, identifying unequal distribution of amniotic fluid, and abnormal flow characteristics. The care required is constant observation of the two fetuses, the amniotic fluid and their heart rates.
Conservative Management (for mild cases): In severe conditions observation and constant assessment of the condition may be needed. This may involve serial ultrasounds and dopplers to monitor the status of the condition of the mother and/or the baby.
Intrauterine Intervention:
Amnioreduction: Removal of excess amniotic fluid from the recipient’s sac to relieve pressure and improve blood flow.
Laser Therapy: Selective laser photocoagulation of the abnormally connected vessels in the placenta aids in correcting the blood flow which is the primary reason for TTTS.
The moderate to severe form of the disease is treated through selective laser photocoagulation.
Septostomy: A procedure where a hole is made in the dividing membrane between the fetuses to allow better fluid distribution.
Post-treatment
Monitoring: Post-intervention, assessment of uterine cavity, fetal heart rate tracking, and overall fetal status of both fetuses.
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