Twin-twin transfusion syndrome - a University Hospital experience with intrauterine treatment

ABSTRACT Introduction: twin-to-twin transfusion syndrome (TTTS), defined by combination of polyhydramnios-oligohydramnios, is the most prevalent (5%-35%) of the abnormalities due to placental vascular anastomoses and the most lethal (80%-100% mortality) if untreated. Fetoscopic laser ablation of abnormal vasculature using the Solomon technique is the gold standard approach. It consists of interrupting the intertwin blood flow. Objectives: to present our initial experience at the Fetal Surgery Service of the Hospital de Clinicas of the Federal University of Parana (HC-UFPR) and to compare our results with those reported in the literature. Methods: we conducted a retrospective analysis of pregnancies who had undergone laser ablation, assessing data on Quintero’s staging, gestational age at diagnosis and at the time of the procedure, placental position, immediate post-procedure survival, and survival after the neonatal period. We then compared these data with the most recent data available in the literature. Results: we analyzed ten TTTS cases. The diagnosis was performed before the 26th week of pregnancy (median 20.8 weeks) and treatment occurred in a median of 9.5 days later. The distribution by the Quintero’s staging was of three cases in stage II, five in stage III, and two in stage IV. In 50% of the gestations, at least one of the fetuses survived through the neonatal period. Conclusion: the treatment of TTTS in the HC-UFPR had a positive impact in the survival of the affected fetuses, although the results were worse than the ones reported in the literature, probably due to the delay in referencing the patients to our service, leading to a prolonged interval between diagnosis and treatment.


INTRODUCTION
T win pregnancies often impose risks on mother and fetuses when compared with non-twin ones 1 .
Monochorionic twin pregnancies are three to 10 times 2 more susceptible to fetal morbidity and mortality 1 . One of the reasons for this is the almost always present vascular anastomoses 3 , which allow the shunting of blood between fetuses 4 and can lead to the development of a group of pathophysiological conditions commonly referred to as "complicated monochorionic twins" 5 .

METHODS
This is a retrospective analysis study of patients For the purposes of this study, we limited the series to patients treated by TTTS, with a confirmed ultrasonographic diagnosis at the HC-UFPR, and undergoing laser ablation via fetoscopy in this service.
We excluded cases of selective intrauterine growth restriction and TRAPS, because although they are also related to the sharing of a placenta by the two fetuses and can be treated by laser ablation, they display different pathophysiology, prognosis, and complications.
We excluded one of the TTTS cases from the analysis due to insufficient information in the medical records. the cauterization of visible anastomoses, followed by the interconnection of these sites by a laser cauterization line, from one end of the placenta to the other, demarcating the placental vascular equator 11 . The purpose of this last step is to completely separate the two parts of the placental chorionic surface 6 . This allows for a reduction in operative time and less damage to normal placental vessels, when compared with selective and non-selective methods used before the description of this technique 11 .
For fetoscopic access, local anesthesia is performed over the entire thickness of the maternal abdominal wall, followed by a small 3 mm incision and ultrasound-guided insertion of the fetoscope in a placenta-free area 12 . Once the fetoscope is positioned, coagulation of vascular anastomoses occurs as described above 13   We excluded three of the cases because they had diagnoses other than TTTS, one of which was diagnosed only as selective IUGR, and the other two, as TTTS was classified ultrasonographically according to the Quintero's staging, treatment being indicated for fetuses in stage II or higher and before the 26 th week of pregnancy, as recommended by the literature. Table 1 shows the Quintero's staging.
We used the Solomon technique for laser ablation of abnormal placental anastomoses via the fetoscopic route, given the greater evidence highlighting the superior effectiveness and less recurrence or inversion of transfusion between fetuses. This approach consists of   (Table   4 and Figure 2).
TRAPS. Of the 11 cases with confirmed TTTS, we excluded one from the analysis due to lack of data in the medical records.
Concerning the ten cases analyzed, the median gestational age at diagnosis was 20.8 weeks, the median gestational age at the time of treatment, 21.6 weeks, the interval between diagnosis and treatment varied between two and 15 days, with a median of 9.5 days ( Table 2).   (Table 3).  1  548  778  Anterior  IV  2  428  548  Anterior  II  3  232  310  Posterior  III  4  161  206  Anterior  II  5  186  264  Lateral  III  6  290  465  Lateral  III  7  99  172  Lateral  III  8  465  ND  Lateral  II  9  225  372  Lateral  IV  10 ND ND Lateral IV Note: ND -no data available

Rezende
Twin-twin transfusion syndrome -a University Hospital experience with intrauterine treatment to the longest perinatal survival 1 . In this sense, it is worth mentioning that we report the initial experience of our service here. Yet, even in a short period, it is possible to notice a trend of improvement in the survival of the last treated cases in relation to the first, as shown in Table 4.
As for the limitations of this study, the main one is the small number of cases, which is partly due to the recent implantation of the technique in the service, as well as the small number of procedures performed due to financial and technical limitations. In addition, since this is a retrospective study, there is the inherent difficult in obtaining data from medical records.
Our analysis demonstrates that it is feasible to provide a highly complex treatment, such as fetoscopic ablation, for cases of TTTS in a public health service in a developing country, since the data showed an improvement in survival in relation to expectant management.

CONCLUSIONS
The treatment of TTTS with laser ablation of placental vessels via fetoscopy at the HC-UFPR Fetal Surgery Service had a positive impact on the survival of the affected fetuses, with a better than expected result.
Without treatment, this survival would be 0%-20%, and with a high incidence of sequelae.
However, these results of fetal survival in the service are still worse than those reported in the literature.
One of the main factors responsible for this is probably the delay between diagnosis and treatment, which should be no longer than 48 hours, while at the HC-UFPR it was up to 15 days (median 9.5).