Syndrome of feto-fetal fetal transfusion: causes, signs, treatment

Feto-fetal syndrome - this is a fairly common phenomenon, although not all heard about it. First of all, this symptom concerns pregnancy, in which the mother expects the twins. To know the main risk factors for this pathology, you need to understand how it occurs and how it manifests itself.

Epidemiology

Statistics show a very serious prevalence of this syndrome. Monozygotic twins are found in 3-5 per 1000 pregnancies. Approximately 75% of monozygotic twins are monochorions. And the development of feto-fetal syndrome occurs in 5-38% of monochorionic twins. A severe syndrome of feto-fetal transfusion is 60-100% fetal or neonatal mortality. The death of one twin is associated with neurological consequences in 25% of surviving twins.

[1], [2], [3]

Causes of the feto-fetal syndrome

Many have heard of such a concept as feto-fetal transfusion syndrome or feto-fetal transfusion syndrome. What it is?

Feto-fetal syndrome is a placenta disease, an organ that develops in the uterus during pregnancy, binds the mother's blood supply to the fetuses and provides nutrition to her descendants. Developing fetal twins are usually normal until anomalies in the bloodstream inside the placenta lead to the onset of the disease process.

The appearance of this syndrome is the result of intrauterine blood transfusion from one twin (donor) to another twin (recipient). Transfusion of blood from a donor double to a recipient twin occurs through placental vascular anastomoses. The most common vascular anastomosis is a deep anastomosis of the artery and vein through a common placental share. This syndrome occurs only in monozygotic (identical) twins with a monochorionic placenta. The twin donor is often smaller, and the birth weight is 20% less than the recipient's birth weight.

Pathology is a specific complication of monozygotic twins with a monochorionic placenta. Monozygotic twins, which have dichoric placentation, are not at risk.

The causes of feto-fetal syndrome are not completely clear. However, it is known that anomalies during the division of the mother's egg after fertilization lead to abnormalities of the placenta, which ultimately can lead to a transfusion syndrome with two twins.

Normal development of identical (monozygotic) twins begins with the fertilization of the mother's egg (egg) with the father's sperm. During the first three days after fertilization, the fertilized ovum (zygote) is divided into two complete identical embryos. These two embryos, which feed on individual placentas (dichorionic) during pregnancy, eventually become two individuals (monozygotic twins) that have almost identical genetic data.

However, in some cases of development of monozygotic twins, the zygote takes more than three days to split into two complete embryos. Scientists have noticed that the longer the zygote is needed for separation, the more problems can arise during pregnancy with twins. If the division of the zygote takes from four to eight days, the twins have a common placenta (monochorionic), and the membrane that separates the two amniotic sacs of the fetus is thin (diamiotic). If the fertilized egg is divided within eight to twelve days, the twins have a common placenta (monochorionic), and there is no separation membrane; therefore, two fetuses essentially separate one amniotic sac (monoamnotic). It was reported that the syndrome of feto-fetal transfusion occurs in both these types of pregnancy (monochorionic-diamionic and monochorionic-monoamnionic). It is unclear why the zygote is divided into twins and why in some cases it takes longer than usual. Feto-fetal syndrome with double is more often with monochorionic diamiotic pregnancy. Therefore, risk factors - this is exactly such a pregnancy, especially if such cases were in the family.

[4], [5], [6]

Pathogenesis

The pathogenesis of the development of the syndrome lies in the features of the blood supply to the children in utero. Most identical twins have a common placenta, in which the blood vessels connect the umbilical cord and the blood circulation of the fetuses (placental anastomoses). The umbilical cord connects the fetal twins to the placenta. In most cases, the blood flow is balanced between twins through these connecting blood vessels. However, when the double transfusion syndrome occurs, the blood begins to flow unevenly through the connective blood vessels. As a result, one fetus-twin receives too much blood (the recipient), while the other receives too little (the donor). Gemini, even if they usually develop up to this point, can now begin to show different symptoms, depending on when there was an imbalance in the bloodstream during pregnancy (transplantation with two twins). Transplantation with two twins can occur at any time during pregnancy. If the imbalance in the blood flow occurs in the early stages of pregnancy (first trimester), one of the fetus twins may simply stop developing; as a result, only one fetus will be detected for the remainder of the pregnancy. If transfusion occurs shortly before birth or during labor, twins may exhibit symptoms associated with sudden absence or excess of blood supply. However, if the syndrome of double transfusion syndrome occurs during pregnancy (in the second trimester), many symptoms may occur.

It is unclear why this imbalance occurs. However, it is believed that several different factors can play a role, including the extent to which the placenta can be unevenly distributed by the two fetuses, the type and number of connective blood vessels (anastomoses) in the common placenta and changes in pressure in the mother's uterus (eg, occurs with polyhydramnios or with contraction of the uterus during labor).

[7], [8], [9], [10], [11], [12], [13]

Symptoms of the feto-fetal syndrome

Symptoms of feto-fetal syndrome develop when there is already a large blood loss that leads to abnormalities. During normal fetal development, most identical (monozygotic) twins grow at about the same speed and have similar weights when they are born. However, if fetal twins have a double blood transfusion syndrome by the middle of pregnancy (second trimester), they can vary greatly depending on the speed and size of the development. While the twin recipient may become larger in size than usual, a twin donor may suffer from a serious slowdown in growth.

The additional blood supply of the recipient twin can cause heart failure, leading to accumulation of fluid in some of its cavities, for example, in the abdominal cavity (ascites), around the lungs (pleural effusion) or around the heart (pericardial effusion). When taking excess blood, there is a constant stress on the heart and blood vessels of the fetus, which can eventually cause congestive heart failure. When a fetus is anemic or lacking blood and oxygen, it tries to use what it most effectively does. This is achieved by emphasizing the flow of blood to the most important organs (brain and heart) and closing down less important organs, such as the kidneys. Thus, the "donor" twin will do much less - and sometimes not - urine. Meanwhile, the recipient twin is overloaded with blood and volume, and as a result has excessive urination. The twin donor is at risk of developing kidney failure and other organs due to insufficient blood flow. Because of the blood vessels that connect the circulation of two fruits across the common placenta, if one of the twins dies, another twin faces a serious risk of death or damage to vital organs.

On the other hand, the donor twin has insufficient blood supply, which can lead to potentially life-threatening anemia and growth restrictions. If the donor's twin develops a severe growth restriction, an insufficient supply of oxygen (hypoxia) to the developing brain can occur during pregnancy or from respiratory distress syndrome. As a result, damage to the brain can occur, which can cause cerebral palsy. Thus, the symptoms can manifest only with ultrasound, in the first place - it's a big difference in the weight of the fruit.

When monochorionic twins with feto-fetal transfusion syndrome occur in the middle of pregnancy, one of the twins may die due to too little blood, too much blood, or too little of the common placenta (severe placental insufficiency). Then the blood can pass from the living twin to the deceased twin. Such reduced blood flow to certain areas of this fetus can be life-threatening or can lead to various developmental abnormalities. In some cases, serious brain trauma can occur, leading to the formation of cysts or cavities in the outer layer of the brain or the absence of cerebral hemispheres of the brain.

But it is important to diagnose the syndrome when the child has not yet died. Therefore, the first signs of the syndrome can be accompanied by such clinical manifestations as sudden increase in abdominal girth, dyspnea, stomach tension, compression and even premature rupture of the placenta.

[14], [15], [16], [17], [18],

Stages

Stages of the syndrome correspond to the degree of severity. They are distinguished on the basis of ultrasound data.

• Stage I: a visible bladder in a twin donor with normal Doppler data. Uneven volume of amniotic fluid.
• Stage II: an empty bladder in a donor twin, and it can not be detected with ultrasound.
• Stage III: an empty bladder in a twin donor, an abnormal blood flow through the umbilical cord and the placenta; it is identified by Doppler ultrasound.
• Stage IV: One or both fetuses retain fluid, causing edema.
• Stage V: The death of one of the fruits.

[19], [20], [21]

Forms

Types of fetal transfusion syndrome depend on when these changes occur, and the later the gestation period, the more likely it is to report healthy babies. Therefore, distinguish between early feto-fetal syndrome and late.

[22], [23], [24], [25], [26]

Complications and consequences

The consequences of the syndrome are more serious if it develops in the early stages. The instability of fetal blood pressure can lead to brain ischemia in both donors or twin recipients. Ischemia of the fetal brain can lead to periventricular leukomalacia, microcephaly and cerebral palsy. The earlier the twins were born, the higher the incidence of postnatal morbidity and mortality.

Neurological complications can also develop against the background of the syndrome. The intrauterine death of one twin can lead to neurological consequences for the surviving twin. The acute involvement of the surviving twin in the relaxed circulation of the deceased twin can lead to intrauterine CNS ischemia.

[27], [28], [29], [30],

Diagnostics of the feto-fetal syndrome

Diagnosis of feto-fetal syndrome is based on instrumental methods. Feto-fetal syndrome can be detected during pregnancy (second trimester) using ultrasonography, a method that creates a fetal image by measuring the reflection of sound waves. With ultrasound, the syndrome can be suspected when one twin has an oligohydramnion, and the hydramnion is noted in another.

General signs of the syndrome can be diagnosed on the basis of some data.

1. Same-sex twins with one placenta.
2. Thin (two-layer) separation membrane between amniotic sacs. The double peak is absent.
3. Combined polyhydramnions and oligohydramnions. The maximum vertical pocket (MVP) is more than 8 cm around the recipient's double and less than 2 cm around the donor fetus. A twin donor can be "stuck" as a result of an oligohydramnion.
4. Signs of hyperhydration or heart failure in both fetuses. This is most often found in a larger recipient.
5. A significant discrepancy in the size of the twins is not always present. When disagreement arises, the donor is a smaller double, and the recipient is larger.

Early signs of feto-fetal syndrome, before the actual "stuck" twin, include a fetus with an aggressively stretched bladder compared to another twin.

To further assess the severity of the feto-fetal syndrome, embryonic echocardiography is often performed. Fetal echocardiograms are specialized, targeted ultrasound examinations of the heart performed by pediatric cardiologists. Early changes in heart failure are usually observed first in the recipient, since it is difficult for his heart to pump excess blood. These instrumental studies may reveal an increased size of some cardiac chambers and changes in flow through the heart valves (eg, tricuspid regurgitation). If stress and congestion remain unprocessed in the recipient, progressive changes may include a decrease in the function of the heart chambers and the possible development of narrowing of one of the heart valves (pulmonary stenosis).

Instrumental diagnostics is not limited to these methods alone. Finally, using information, both from the echocardiogram and the obstetric ultrasound survey, we are looking for patterns of blood flow in the umbilical artery and vein and other large blood vessels of the fetus. Blood in the umbilical artery usually flows from the fetus and to the placenta, trying to get fresh oxygen and nutrients from the bloodstream of the mother. If the placenta condition worsens, it becomes increasingly difficult to leak blood into the placenta and inside it. With each heart rhythm the fruit pushes the blood to the placenta (in the phase of the systole) through the umbilical artery, and usually this rhythm is strong enough that the blood continues to flow forward to the placenta, even when the heart is again filled for the next. In some cases, as the feto-fetal syndrome progresses, the direct flow in the donor's umbilical artery may decrease between cardiac contractions. If the condition worsens, there can be no flow during refilling the fetal heart.

All results of the study of echocardiogram and ultrasound are taken into account when determining the severity of feto-fetal for each individual pregnancy.

Analyzes are not specific for this syndrome, therefore, all planned analyzes a woman should take according to schedule.

[31], [32], [33], [34]

Differential diagnosis

Differential diagnosis of feto-fetal syndrome is performed with syndromes, the symptoms of which can be similar to the syndrome of double transfusion. Acarial twinning is a rare disorder that sometimes occurs when women are pregnant with identical (monozygotic) twins. Several cases have also been reported in identical triplets. In akardialnyj twinning there is a direct communication of one of two umbilical arteries of one twin with two twins having only one umbilical artery and a vein. Some researchers believe that twins can initially experience normal early embryonic development. However very early in the beginning of pregnancy the blood begins to flow incorrectly through the connecting umbilical artery of the fetus to the artery connection, and one twin starts circulating for both fruits.

Depending on when this imbalance in the bloodstream occurs during pregnancy, another developing twin may not develop normally, which leads to a lack of cardiac structure or the presence of very primitive cardiac structures. In all cases, this twin (acardic twin) also exhibits other major anomalies, such as the absence of head structures or the brain. In most cases, the double does not show any developmental defects; However, a permanent deformation on the heart from the need to inject blood to another twin can cause him to have heart failure. In case of a concomitant twinning, an excess of amniotic fluid (hydramnion) can be observed, which leads to the fact that the mother's uterus grows faster than usual for her pregnancy stage. The cause of the concomitant twinning is unknown.

Treatment of the feto-fetal syndrome

In the treatment of feto-fetal syndrome to date, there are six therapeutic options:

1. conservative management without intervention;
2. termination of pregnancy;
3. selective fetocid;
4. therapeutic amnioreduction;
5. amniotic septostomy;
6. endoscopic ablation of communicating vessels.

Of these methods, therapeutic amniioreduction is probably the most widely used and accepted treatment method, although endoscopic laser ablation is gaining popularity.

Surgical treatment has advantages, because the speed of the outcome depends on the life of babies. Because transfusion syndrome is a progressive disorder, early treatment can prevent complications, including premature delivery and premature rupture of membranes due to excessive fluid (polyhydramnion). The choice of method of treatment of the syndrome depends on the severity of the condition and the current phase of your pregnancy. All patients with stage II, III or IV, and some patients with stage I - should study and consider embryonic intervention. In most cases, a suitable optimal therapy will be fetoscopic laser intervention.

Amnioreduction or amniocentesis is a procedure that involves draining the excess amniotic fluid. Using ultrasonic guidance, the needle is placed in the recipient's bag, and 2-3 liters of liquid are carefully removed. This therapy is aimed at preventing the risk of premature births from excessive stretching of the uterus. In addition, by reducing the volume of fluid, a reduction in pressure of the intra-amniotic and placental vasculature was obtained, which improves placental blood flow. As the main cause of the syndrome continues, the liquid in the bag re-accumulates. Consequently, amniioreduction may need to be repeated several times during pregnancy.

Amniocentesis can be combined with "septostomy". In this procedure, the liquid is first drained from the amniotic sac, and then the needle is used to create a small opening in the membrane between the two amniotic cavities of the twins. This allows the amniotic fluid to pass into the donor twin sack. Septostomy allows you to balance the volumes of amniotic fluid between twins. Operation of an amniotic fluid, such as amniodrainage or septostomy, can alleviate symptoms and can alleviate problems in some patients. However, since anastomoses remain open, the risks of unbalanced volume exchange also remain - the main problem is not being eliminated.

Laser coagulation of placental anastomoses is carried out by introducing a thin fiber-optic tube through the abdominal wall of the mother and through the uterine wall into the amniotic cavity of the recipient double. Investigating the blood vessels on the surface of the placenta directly, the abnormal vascular connections between the twins can be found and eliminated by sending a laser beam to them. Only those vessels that go from one twin to the other are coagulated by a laser beam. Normal blood vessels that help feed each twin remain intact.

A detailed ultrasound scan prior to the procedure demonstrates the places where the umbilical ligaments attach to the common placenta and can help detect abnormal interchain connections, which makes it easier and quicker to identify the process with the fetoscope. After the laser procedure is completed, amnioration (removal of excess amniotic fluid) is performed to reduce the likelihood of early delivery and help make pregnancy more comfortable.

Births after feto-fetal syndrome, as a rule, are planned by conducting cesarean section.

Selective fetocid includes the interruption of blood transfusion by deliberately necrosis of one twin. It is recommended to use in the early stages, when other methods are ineffective and one child can lead to death of another, and then you can lose both. This process is necessary for all vascular connections to be occluded simultaneously, for the purpose of which the umbilical cord occlusion is used.

Occlusion of the umbilical cord is a procedure that is performed inside the uterus through a shell placed by an ultrasound guide in a bag of one twin, usually a donor (smaller). A special tweezer grasps the cord, and an electric current passes between the tweezers, coagulating the blood vessels of the umbilical cord of this fruit. This stops the flow of blood, and this child dies.

A surviving child usually does not have long-term effects. As with any intrauterine invasive procedure, short-term complications may occur, including premature birth, rupture of membranes, infection or bleeding. But in more than 90% of cases the procedure leads to the fact that one live baby, born in the near future, has no permanent shortcomings. This procedure is technically feasible and usually not long, so maternal operational complications are very rare.

Alternative treatment and homeopathy with feto-fetal syndrome is not used.

Prevention

Prevention of the development of the syndrome is a very complex issue, since there are no specific methods.

[35], [36], [37], [38]

Forecast

The prognosis of the feto-fetal syndrome depends on the stage and degree of severity of fetal discordance. The average survival rate is 50-65%; this figure is 77% if the treatment started during the first stage. If we compare the prognosis after different treatments, we found that 76% of the survival of at least one fetus and 36% of the survival of both twins using a laser, compared with 51% of the survival of at least one fetus and 26% of the survival of both twins with amniiorduction.

Feto-fetal syndrome is a relatively common and serious complication of monochorionic pregnancy. The diagnosis should be suspected in any pregnancy with a sudden increase in abdominal coverage, and you can confirm with ultrasound. But there are methods of treatment and it is worth remembering that the earlier treatment is started, the greater the chance to preserve both fetuses.

[39], [40], [41]