Definition and diagnosis of twin transfusion syndrome (TTTS)
TTTS is a unique complication of monochorionic twins, It accounts for 10% ~ 15% of monochorionic twins, and its pathogenesis is still unclear. It is mainly related to the common placenta of monochorionic twins and a large number of vascular anastomoses at the placenta level. The fetal mortality rate of untreated TTTS 24 weeks ago can reach 90% ~ 100%, and the proportion of neurological sequelae in surviving fetuses is as high as 17% ~ 33% even if they survive.
The diagnostic criteria for TTTS are: During ultrasound follow-up of monochorionic twins, If a fetus has too much amniotic fluid (the maximum depth of amniotic fluid is greater than 8cm before 20 weeks of pregnancy, After 20 weeks of gestation, the maximum depth of amniotic fluid is greater than 10cm), while the other fetus has oligohydramnios (the maximum depth of amniotic fluid is less than 50px). The previous diagnostic criteria of [20% difference in weight and 5 g/L difference in hemoglobin between the two fetuses] have been abandoned. The necessary condition for TTTS diagnosis is that the two fetuses have polyhydramnios-oligohydramnios sequence, not whether there is difference in weight between the two fetuses.
It is suggested that TTTS should be vigilant for pregnant women with monochorionic twins if their abdominal circumference is obviously increased or abdominal distension is obvious in a short period of time. If abnormal amniotic fluid volume is found by ultrasound, it is recommended to refer to a regional conditional prenatal diagnosis or fetal medical center for definite diagnosis.
Staging of TTTS
Regarding the staging of TTTS, At present, the most commonly used stage is Quintero stage. First proposed by Dr. Quintero of the United States in 1999, This stage is mainly based on the severity of the disease. Although it is currently the most commonly used stage in clinical practice, one of its biggest disadvantages is that it has no obvious correlation with the prognosis of children, and the progress of TTTS can develop in leaps and bounds, so attention should be paid to it in clinical application.
Quintero Staging of TTTS
For the treatment of TTTS, The earliest method was amniotic fluid reduction, The aim is to prolong the gestational age by reducing amniotic cavity pressure. The survival rate of at least one fetus after operation is about 50% ~ 60%. At present, the most commonly used method is to coagulate blood vessels between placentas under fetal microscope. Compared with amniotic fluid reduction, this more advanced method can obviously improve the prognosis of TTTS children. The survival rate of one fetus after fetoscopic treatment is obviously increased, the incidence rate of neurological sequelae is also reduced, and the average gestational age after delivery is later than that after amniotic fluid reduction.
At present, the indications for TTTS treatment by fetoscopy are Quintero II ~ IV. For TTTS stage I, The prognosis of TTTS stage I depends to some extent on whether the disease progresses, and about 10% ~ 45.5% of the cases will deteriorate. This uncertainty of prognosis is the reason why TTTS stage I patients need fetoscopic laser therapy.
The best gestational age for fetoscopic treatment is 16 ~ 26 weeks of pregnancy. Fetoscopic treatment of TTTS before and after 16 weeks of pregnancy has also been carried out in a few centers. David et al. Reported 325 cases of TTTS treated with fetoscopy. The operation time of 283 cases was from 17 weeks to 26 weeks of pregnancy. The survival rate of one fetus was 86.9%, The survival rate was 56.6%, In 24 cases, the operation time was earlier than 17 weeks, The operation time of 18 cases was later than that of 26 cases, The success rate of operation was similar to that of 17 ~ 26 weeks of pregnancy. Since 2004, More than 10,000 cases of TTTS have been performed worldwide, and the effect of fetoscopic laser surgery for TTTS has been widely recognized. In recent years, many centers in China have carried out fetoscopic laser surgery. The results show that the survival rate of at least one fetus after laser surgery is 60% ~ 87.9%, the survival rate of two fetuses is 51.5%, and the average gestational age of delivery is 33 ~ 34 weeks.
Suggestion: For TTTS of 16 ~ 26 weeks of pregnancy, stage II and above, fetal endoscopic laser therapy should be the first choice, and TTTS treatment should be carried out in fetal medical centers capable of intrauterine intervention.
Current Problems in Diagnosis and Treatment of TTTS in China
Incorrect diagnosis: The diagnosis of TTTS requires rich clinical experience, especially the specialist of fetal medicine who has received formal ultrasound training. Many of the [TTTS] patients referred by our hospital are not TTTS. These people do not need fetal endoscopic surgery at all. It is very dangerous to blindly carry out fetal endoscopic laser therapy if the diagnosis is inaccurate.
Inappropriate referral time: TTTS has an ideal [time window] for fetal endoscopic laser therapy. This [time window] is 16-26 weeks of pregnancy. If this [time window] is missed, the therapeutic effect cannot be well guaranteed, so early diagnosis and correct diagnosis are very important.
Inappropriate Termination of Pregnancy and Fetal Reduction: Because some medical institutions are unable to carry out fetal endoscopic laser treatment, TTTS patients will be advised to undergo amniotic fluid reduction, radiofrequency ablation to reduce fetus, or even twin induction of labor. In fact, this is not appropriate. The responsible approach is to inform the patient of all the options and help the patient make the most reasonable decisions and choices. If he cannot carry out them himself, he should refer the patient to the most suitable fetal medical center for further diagnosis and treatment.
How to Choose a Suitable Fetal Medical Center
For expectant mothers with suspected TTTS, it is very important to choose a suitable fetal medical center for further diagnosis and treatment. In the process of selecting medical institutions and doctors, it is best to understand the following issues in detail:
1. Clinical Experience of Fetal Medical Team
2. Number of cases of diagnosis and treatment of twins and multiple births per year
3. Whether various schemes can be provided for the treatment of TTTS, including amniotic fluid reduction, radiofrequency ablation and fetal reduction, twin labor induction and fetal endoscopic laser therapy.
4. The cumulative number of treatment cases and success rate of various TTTS treatments, especially fetal endoscopic laser therapy, including the percentage of survival of at least one child and survival of two children.
Author: Duan Tao
The article was reprinted by Clove Garden authorized by the author.