Residual vascular communications in twin-twin transfusion syndrome treated with sequential laser surgery: frequency and clinical implications

Placental architectural characteristics following laser ablation within monochorionic twins complicated by twin-twin transfusion syndrome: A systematic review and meta-analysis of outcomes

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) complicates approximately 10%-15% of all monochorionic twin pregnancies. The aim of this review was to evaluate the placental architectural characteristics within TTTS twins following laser and elucidate their impact on fetal outcomes and operative success.

MATERIAL AND METHODS

Five databases were searched from inception to August 2023. Studies detailing post-delivery placental analysis within TTTS twins post-laser were included. Studies were categorized into two main groups: (1) residual anastomoses following laser and (2) abnormal cord insertion: either velamentous and/or marginal or proximate. The primary outcome was to determine the proportion of TTTS placentas with residual anastomoses and abnormal cord insertions post-laser. Secondary outcomes included assessing residual anastomoses on post-laser fetal outcomes and assessing the relationship between abnormal cord insertion and TTTS development. Study bias was critiqued using the Joanna Briggs Institute checklists and Cochrane risk of bias tool. Random-effects meta-analysis was used, and results were reported as pooled proportions or odds ratio (OR) with 95% confidence interval (CI). PROSPERO registration: CRD42023476875.

RESULTS

Twenty-six studies, comprising 4013 monochorionic twins, were included for analysis. The proportion of TTTS placentas with residual anastomoses following laser was 24% (95% CI, 0.12-0.41), with a mean and standard deviation of 4.03 ± 2.95 anastomoses per placenta. Post-laser residual anastomoses were significantly associated with intrauterine fetal death (OR, 2.38 [95% CI, 1.33-4.26]), neonatal death (OR, 3.37 [95% CI, 1.65-6.88]), recurrent TTTS (OR, 24.33 [95% CI, 6.64-89.12]), and twin anemia polycythemia sequence (OR, 13.54 [95% CI, 6.36-28.85]). Combined abnormal cord (velamentous and marginal), velamentous cord, and marginal cord insertions within one or both twins following laser were reported at rates of 49% (95% CI, 0.39-0.59), 27% (95% CI, 0.18-0.38), and 28% (95% CI, 0.21-0.36), respectively. Combined, velamentous and marginal cord insertions were not significantly associated with TTTS twins requiring laser (p = 0.72, p = 0.38, and p = 0.71, respectively) versus non-TTTS monochorionic twins.

CONCLUSIONS

To the best of our knowledge, this is the first review to conjointly explore outcomes of residual anastomoses and abnormal cord insertions within TTTS twins following laser. A large prospective study is necessitated to assess the relationship between abnormal cord insertion and residual anastomoses development post-laser.

Solomon versus selective fetoscopic laser photocoagulation for twin-twin transfusion syndrome: A systematic review and meta-analysis

This meta-analysis aims to compare the perinatal outcome of twin-twin transfusion syndrome (TTTS) pregnancies undergoing selective versus vascular equator (Solomon) fetoscopic laser photocoagulation (FLP). We performed a systematic search in PubMed and Web of Science from inception up to 25 July 2021. Studies comparing the Solomon and selective techniques of FLP for treatment of TTTS pregnancies were eligible. Random-effects or fixed-effect models were used to pool standardized mean differences (SMD) and log odds ratio. Seven studies with a total of 1664 TTTS pregnancies (n = 671 undergoing Solomon and n = 993 selective techniques) were included. As compared to the selective FLP, Solomon was associated with a lower risk of recurrent TTTS compared to the selective technique (Log odds ratio [OR]: -1.167; 95% credible interval [CrI]: -2.01, -0.33; p = 0.021; I² : 67%). In addition, Solomon was significantly associated with a higher risk of placental abruption than the selective technique (Log [OR]: 1.44; 95% CrI: 0.45, 2.47; p = 0.012; I² : 0.0%). Furthermore, a trend for the higher risk of preterm premature rupture of membranes was observed among those undergoing Solomon (Log [OR]: 0.581; 95% CrI: -0.43, 1.49; p = 0.131; I² : 17%). As compared to selective FLP, the Solomon technique for TTTS pregnancies is associated with a significantly lower recurrence of TTTS; however, it significantly increases the risk of placental abruption.

Twin-to-twin transfusion syndrome: Controversies in the diagnosis and management

In twin-to-twin transfusion syndrome (TTTS) communicating placental vessels on the chorionic plate between the donor and recipient twins are responsible for the chronic imbalance of blood flow. Evidence demonstrates that fetoscopic laser ablation is superior to serial amnioreductions in terms of survival and neurological outcome for stages II-IV TTTS. However, the optimal management of stage I TTTS remains poorly understood. It is well established that all chorionic plate anastomoses should be closed by laser ablation. Compared to the selective laser method, the Solomon technique yields a significant reduction of recurrent TTTS and post-laser twin anemia polycythemia sequence (TAPS). Over the past 25 years, survival rates after fetoscopic laser surgery have significantly increased. High volume centers report up to 70% double survival and at least one survivor in >90% cases. In this review, we discuss the controversies in the diagnosis and management of TTTS, especially, the optimal management in stage I cases, very early or late diagnosis, and the optimal laser technique. Furthermore, we will discuss a stage-related outcome after laser surgery and examine whether it is necessary at all to distinguish between stages I and II. Finally, the optimal timing as well as mode of delivery after TTTS laser treatment will be discussed.

Perinatal outcome of pregnancy complicated by twin anemia-polycythemia sequence: systematic review and meta-analysis

OBJECTIVE

To report the perinatal outcome of monochorionic diamniotic (MCDA) twin pregnancies complicated by twin anemia-polycythemia sequence (TAPS), according to the type of TAPS (spontaneous or postlaser) and the management option adopted.

METHODS

MEDLINE, EMBASE and The Cochrane Library databases were searched for studies reporting on the outcome of twin pregnancies complicated by TAPS. Inclusion criteria were non-anomalous MCDA twin pregnancies with a diagnosis of TAPS. The primary outcome was perinatal mortality; secondary outcomes were neonatal morbidity and preterm birth (PTB). The outcomes were stratified according to the type of TAPS (spontaneous or following laser treatment for twin-twin transfusion syndrome) and the management option adopted (expectant, laser surgery, intrauterine transfusion (IUT) or selective reduction (SR)). Random-effects meta-analysis of proportions was used to analyze the data.

RESULTS

Perinatal outcome was assessed according to whether TAPS occurred spontaneously or after laser treatment in 506 pregnancies (38 studies). Intrauterine death (IUD) occurred in 5.2% (95% CI, 3.6-7.1%) of twins with spontaneous TAPS and in 10.2% (95% CI, 7.4-13.3%) of those with postlaser TAPS, while the corresponding rates of neonatal death were 4.0% (95% CI, 2.6-5.7%) and 9.2% (95% CI, 6.6-12.3%), respectively. Severe neonatal morbidity occurred in 29.3% (95% CI, 25.6-33.1%) of twins after spontaneous TAPS and in 33.3% (95% CI, 17.4-51.8%) after postlaser TAPS, while the corresponding rates of severe neurological morbidity were 4.0% (95% CI, 3.5-5.7%) and 11.1% (95% CI, 6.2-17.2%), respectively. PTB complicated 86.3% (95% CI, 77.2-93.3%) of pregnancies with spontaneous TAPS and all cases with postlaser TAPS (100% (95% CI, 84.3-100%)). Iatrogenic PTB was more frequent than spontaneous PTB in both groups. Perinatal outcome was assessed according to the management option adopted in 417 pregnancies (21 studies). IUD occurred in 9.8% (95% CI, 4.3-17.1%) of twins managed expectantly and in 13.1% (95% CI, 9.2-17.6%), 12.1% (95% CI, 7.7-17.3%) and 7.6% (95% CI, 1.3-18.5%) of those treated with laser surgery, IUT and SR, respectively. Severe neonatal morbidity affected 27.3% (95% CI, 13.6-43.6%) of twins in the expectant-management group, 28.7% (95% CI, 22.7-35.1%) of those in the laser-surgery group, 38.2% (95% CI, 18.3-60.5%) of those in the IUT group and 23.3% (95% CI, 10.5-39.2%) of those in the SR group. PTB complicated 80.4% (95% CI, 59.8-94.8%), 73.4% (95% CI, 48.1-92.3%), 100% (95% CI, 76.5-100%) and 100% (95% CI, 39.8-100%) of pregnancies after expectant management, laser surgery, IUT and SR, respectively.

CONCLUSIONS

The present meta-analysis provides pooled estimates of the risks of perinatal mortality, neonatal morbidity and PTB in twin pregnancies complicated by TAPS, stratified by the type of TAPS and the management option adopted. Although a direct comparison could not be performed, the results from this systematic review suggest that spontaneous TAPS may have a better prognosis than postlaser TAPS. No differences in terms of mortality and morbidity were observed when comparing different management options for TAPS, although these findings should be interpreted with caution in view of the limitations of the included studies. Individualized prenatal management, taking into account the severity of TAPS and gestational age, is currently the recommended strategy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Twin-Twin Transfusion Syndrome Complicated by Proximate Placental Cord Insertion Sites: Endoscopic Clip-Assisted Laser Occlusion

INTRODUCTION

Severe twin-twin transfusion syndrome (TTTS) with a large vascular communication between proximate placental cord insertion sites is a therapeutic dilemma because laser ablation may cause thermal injury to the cord roots and subsequent fetal demise.

CASE PRESENTATION

Stage IV TTTS with placental cord insertion sites 1.3 cm apart and with an intervening large arterio-arterial (AA) anastomosis presented for treatment. The application of endoclips onto the large AA anastomosis between the cord roots allowed for successful laser occlusion using minimal energy. Both the donor and recipient twins were alive and well at 6 months of age.

CONCLUSION

Endoscopic clip-assisted laser occlusion of a placental vessel is technically feasible and may be a useful therapeutic option in select cases.

Update on twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) is a serious complication that affects 10-15% of monochorionic multiple pregnancies. Communicating placental vessels on the chorionic plate between the donor and recipient twin are responsible for the imbalance of blood flow. There is evidence for the superiority of fetoscopic laser ablation over serial amnioreductions regarding survival and neurological outcome for stages II-IV TTTS. However, the optimal management of stage I is still debated. The "Solomon" technique showed a significant reduction in recurrent TTTS and post laser twin anemia-polycythemia sequence (TAPS) in comparison to the selective laser method without improvement in perinatal mortality or neonatal morbidity. Survival rates after fetoscopic laser surgery have significantly increased over the last 25 years. High volume centers report up to 70% double survival and at least one survivor in >90%. Long-term neurodevelopmental impairment occurs in about 10% of children after laser surgery. In this review we discuss the optimal management, innovations in laser technique, long-term neurodevelopmental outcome, and future aspects of TTTS treatment.

Noninvasive high-intensity focused ultrasound treatment of twin-twin transfusion syndrome: A preliminary in vivo study

We investigated the efficacy, maternofetal responses, and safety of using high-intensity focused ultrasound (HIFU) for noninvasive occlusion of placental vasculature compared to sham treatment in anesthetized pregnant sheep. This technique for noninvasive occlusion of placental vasculature may be translatable to the treatment of conditions arising from abnormal placental vasculature, such as twin-twin transfusion syndrome (TTTS). Eleven pregnant sheep were instrumented with maternal and fetal arterial catheters and time-transit flow probes to monitor cardiovascular, acid-base, and metabolic status, and then exposed to HIFU (n = 5) or sham (n = 6) ablation of placental vasculature through the exposed uterine surface. Placental vascular flow was occluded in 28 of 30 targets, and histological examination confirmed occlusion in 24 of 30 targets. In both HIFU and sham exposures, uterine contact reduced maternal uterine artery flow, but delivery of oxygen and glucose to the fetal brain remained normal. HIFU can consistently occlude in vivo placental vessels and ablate blood flow in a pregnant sheep model. Cardiovascular and metabolic fetal responses suggest that the technique is safe in the short term and potentially translatable to human pregnancy.

Laser Treatment of Twin–to–Twin Transfusion Syndrome

Objective: Laser ablation of all placental vascular anastomoses is the optimal treatment for twin–twin transfusion syndrome (TTTS). However, two important controversies are apparent in the literature: (a) a gap between concept and performance, and (b) controversy regarding whether all the anastomoses can be identified endoscopically and whether blind lasering of healthy placenta is justified. The purpose of this article is: (a) to address the potential source of the gap between concept and performance by analyzing the fundamental steps needed to successfully accomplish the surgery, and (b) to discuss the resulting competency benchmarks reported with the different surgical techniques. Materials and Methods: Laser surgery for TTTS can be broken down into two fundamental steps: (1) endoscopic identification of the placental vascular anastomoses, (2) laser ablation of the anastomoses. The two steps are not synonymous: (a) regarding the endoscopic identification of the anastomoses, the non-selective technique is based upon lasering all vessels crossing the dividing membrane, whether anastomotic or not. The selective technique identifies and lasers only placental vascular anastomoses. The Solomon technique is based on the theory that not all anastomoses are endoscopically visible and thus involves lasering healthy areas of the placenta between lasered anastomoses, (b) regarding the actual laser ablation of the anastomoses, successful completion of the surgery (i.e., lasering all the anastomoses) can be measured by the rate of persistent or reverse TTTS (PRTTTS) and how often a selective technique can be achieved. Articles representing the different techniques are discussed. Results: The non-selective technique is associated with the lowest double survival rate (35%), compared with 60–75% of the Solomon or the Quintero selective techniques. The Solomon technique is associated with a 20% rate of residual patent placental vascular anastomoses, compared to 3.5–5% for the selective technique (p < .05). Both the Solomon and the selective technique are associated with a 1% risk of PRTTTS. Adequate placental assessment is highest with the selective technique (99%) compared with the Solomon (80%) or the ‘standard’ (60%) techniques (p < .05). A surgical performance index is proposed. Conclusion: The Quintero selective technique was associated with the highest rate of successful ablation and lowest rate of PRTTTS. The Solomon technique represents a historical backward movement in the identification of placental vascular anastomoses and is associated with higher rate of residual patent vascular communications. The reported outcomes of the Quintero selective technique do not lend support to the existence of invisible anastomoses or justify lasering healthy placental tissue.

Decreased Total Placental Mass Found in Twin-Twin Transfusion Syndrome Gestations with Selective Growth Restriction

Introduction: We examined placental weight characteristics associated with donor selective intrauterine growth restriction (SIUGR) among patients with twin-twin transfusion syndrome (TTTS) who underwent laser surgery. Materials and Methods: Fresh placental specimens were studied. Pregnancies with higher-order multiples, fetal demise, or disrupted or nonsubmitted placental specimens were excluded. Placental characteristics prospectively collected included total placental weight, individual placental weight, and placental share. Data were compared between pregnancies with SIUGR (TTTS + SIUGR group) and those without SIUGR (TTTS-only group). Results: Of 369 consecutive patients who underwent laser surgery for TTTS, 155 (42%) met inclusion criteria: 91 with TTTS + SIUGR and 64 with TTTS-only. Compared to the TTTS-only group, patients in the TTTS + SIUGR group had a lower total placental weight (608 ± 163 vs. 687 ± 224 g, p = 0.012), with a lower donor individual placental weight (237 ± 91 vs. 291 ± 124 g, p = 0.002), but no apparent difference in the individual placental weight of recipient twins (371 ± 109 vs. 396 ± 133 g, p = 0.211). Donor placental share was smaller in those pregnancies affected by SIUGR (38.7 ± 9.6 vs. 42.3 ± 9.8%, p = 0.029). Discussion: TTTS patients with SIUGR had a lower total placental weight and a lower donor individual placental weight compared to those without SIUGR. These findings suggest that differences in donor individual placental weights for SIUGR gestations may not solely be related to differences in placental share.

Selective Reduction Using Intravascular Potassium Chloride Injection after Laser Surgery for Twin-Twin Transfusion Syndrome

Selective reduction (SR) via intravascular potassium chloride (KCl) injection is contraindicated in monochorionic twins due to the presence of placental vascular communications, which may serve as a conduit for inter-twin passage of KCl or allow exsanguination of the living twin into the demised twin. After successful selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS), the twins' circulatory systems are rendered independent. Theoretically, intravascular KCl injection into one twin after successful SLPCV should not result in passage of the feticidal agent nor cause hemodynamic alterations in the co-twin. We describe 3 cases of 1,069 patients (0.3%) that underwent SLPCV for TTTS between 2003 and 2013 and subsequent SR. SLPCV was successfully completed at 180, 226, and 230 weeks' gestational age for Quintero stages III, IV, and III TTTS, respectively. SR via intravascular KCl injection was later performed at maternal request due to the risk of neurological compromise in one twin at 226, 254, and 236 weeks' gestational age. All co-twins survived after SR, and no neurological sequelae were suspected after birth. Further study is necessary before SR can be routinely considered after laser surgery for TTTS.

Pre-Operative Twin Anemia/Polycythemia in the Setting of Twin-Twin Transfusion Syndrome (TTTS)

Introduction: Twin-twin transfusion syndrome (TTTS) and twin anemia-polycythemia sequence (TAPS) are classified as distinct clinical disorders associated with unbalanced blood flow through placental vascular communications. Typically, TAPS placentas demonstrate few <1 mm arteriovenous (AV) communications, and at fetoscopy the twins are visibly pale and plethoric. Materials and Methods: In a cohort of TTTS patients who underwent laser surgery, those with preoperative findings suggestive of anemia/polycythemia (AP) were compared to those with TTTS alone. AP was defined as middle cerebral artery peak systolic velocity in one twin >1.5 multiples of the median (MoM), and <1.0 MoM in the other. Results: Of 369 TTTS patients, 9 (2.4%) met criteria for preoperative AP. The mean number (±SD) of AV communications in the TTTS + AP group was 5.6 ± 5.7, compared with 8.8 ± 4.8 in the TTTS-alone group (p = 0.013). Five TTTS + AP patients (56%) had a few thin AV communications (mean 2.8 ± 1.6); all 5 had visibly pale and plethoric twins. The remaining 4 (44%) had large or numerous anastomoses (mean 10.5 ± 6.8); none had fetal skin color discordance. Discussion: Preoperative AP affected 2% of TTTS patients. Of these, approximately half had placental and skin color findings typically reported with isolated TAPS.

Treatment of Complicated Spontaneous Twin Anemia-Polycythemia Sequence via Fetoscopic Laser Ablation of the Vascular Communications

Monochorionic diamniotic twins share a single placenta and have intertwin vascular communications that link the circulatory systems of the twins together. Twin anemia-polycythemia sequence (TAPS) is an atypical form of twin-twin transfusion syndrome (TTTS) caused by net transfer of blood from one fetus to the other and is characterized by large intertwin hemoglobin differences in the absence of oligohydramnios and polyhydramnios. This condition may develop spontaneously (sTAPS) or as a result of residual vascular communications after prior laser surgery. Because of the relatively low prevalence and lack of clinical awareness, the natural history of sTAPS is unclear and the antenatal treatment remains controversial. Case series of sTAPS have described expectant management with timed delivery, intrauterine blood transfusion, and fetoscopic laser treatment. Favorable outcomes have been described in cases of uncomplicated sTAPS that underwent conservative measures. However, we believe that there may be a subgroup of high-risk or complicated sTAPS patients that may benefit from definitive treatment afforded by fetoscopic laser therapy. We describe 3 complicated cases of sTAPS successfully treated with selective laser photocoagulation of communicating vessels. In 2 of the cases, placental pathology identified thrombosed fetal vessels of the polycythemic twin.

Pathophysiological mechanisms of high-intensity focused ultrasound-mediated vascular occlusion and relevance to non-invasive fetal surgery

High-intensity focused ultrasound (HIFU) is a non-invasive technology, which can be used occlude blood vessels in the body. Both the theory underlying and practical process of blood vessel occlusion are still under development and relatively sparse in vivo experimental and therapeutic data exist. HIFU would however provide an alternative to surgery, particularly in circumstances where serious complications inherent to surgery outweigh the potential benefits. Accordingly, the HIFU technique would be of particular utility for fetal and placental interventions, where open or endoscopic surgery is fraught with difficulty and likelihood of complications including premature delivery. This assumes that HIFU could be shown to safely and effectively occlude blood vessels in utero. To understand these mechanisms more fully, we present a review of relevant cross-specialty literature on the topic of vascular HIFU and suggest an integrative mechanism taking into account clinical, physical and engineering considerations through which HIFU may produce vascular occlusion. This model may aid in the design of HIFU protocols to further develop this area, and might be adapted to provide a non-invasive therapy for conditions in fetal medicine where vascular occlusion is beneficial.

Ultrasound in twins: dichorionic and monochorionic

The objective of this review is to assess the evidence that supports the use of ultrasound in twin pregnancies. Although many of the indications for obstetric ultrasound are the same in both singleton and multiple gestations, there are special considerations as well as unique conditions in twins that require additional imaging studies. The reasons for ultrasound in twins include pregnancy dating, determination of chorionicity, nuchal translucency assessment, anatomical survey, placental evaluation, cervical length assessment, routine fetal growth, and serial surveillance of pregnancies complicated by anomalies, cervical shortening, fetal growth disturbances, and amniotic fluid abnormalities. Twins with monochorionic placentation require heightened scrutiny for monoamnionicity, conjoined twins, twin reversed arterial perfusion (TRAP) syndrome, twin-twin transfusion syndrome, unequal placental sharing with discordant twin growth or selective intrauterine fetal growth restriction (IUGR), twin anemia-polycythemia sequence (TAPS), and single fetal demise. Ultrasound is essential for the detection and management of conditions that can complicate dichorionic and monochorionic twin pregnancies.

Outcome after fetoscopic selective laser ablation of placental anastomoses vs equatorial laser dichorionization for the treatment of twin-to-twin transfusion syndrome

OBJECTIVE

The objective of the study was to compare the outcome in women with twin-twin transfusion syndrome (TTTS) who were managed by selective laser ablation of placental anastomoses (S-LASER) vs equatorial dichorionization of the anastomoses and chorionic plate (ED-LASER).

STUDY DESIGN

We conducted an analysis of 2 consecutive cohorts with TTTS treated with S-LASER and ED-LASER. Preoperative, procedural, delivery, and outcome details were compared between treatment groups.

RESULTS

A total of 147 twin pregnancies had laser (S-LASER, n = 71; ED-LASER, n = 76). Obstetric history, Quintero stage, placental location, individual arterial and venous Doppler parameters, and gestational age at laser and delivery did not differ. Use of lens fetoscope (96.1% vs 50.7%), coagulated anastomosis count (11 vs 15, P < .001), complete equatorial plate visualization (77.5% vs 92.1%, P = .019), and amniotic fluid transparency (80.3% vs 94.7%, P = .011) was greater during ED-LASER. Procedure-related complications, gestational age at delivery, and perinatal details were comparable between groups. ED-LASER was associated with significantly lower recurrence of TTTS (3.9% vs 8.5%), twin anemia polycythemia sequence (2.6% vs 4.2%), and amniotic fluid abnormalities (0% vs 5.6%, P < .05 for all comparisons). Logistic regression identified complete visualization of the equator as the primary determinant for successful TTTS treatment and coagulation of the chorionic plate as an independent cofactor. Double survival at age 6 months was significantly higher after ED-LASER (68.4% vs 50.7%, P < .05), attributable to a lower postlaser and neonatal mortality rates.

CONCLUSION

In patients with TTTS, photocoagulation of causative anastomoses and the chorionic plate along the vascular equator decreases recurrence without increasing adverse outcome and improves survival compared with the selective technique.

Perioperative characteristics associated with preterm birth in twin-twin transfusion syndrome treated by laser surgery

OBJECTIVE

To identify perioperative risk factors for preterm delivery (PTD) in laser-treated patients with twin-twin transfusion syndrome (TTTS).

STUDY DESIGN

Twin-twin transfusion syndrome patients who underwent laser surgery were followed prospectively. Univariate and multivariate analyses were performed to identify gestational and surgical characteristics associated with preterm delivery.

RESULTS

Of 318 eligible patients, the mean (SD) gestational age of delivery was 32.8 (4.2) weeks. The number of days from laser surgery to delivery had a bimodal distribution; group I delivered within 21 days and group II delivered after 21 days of surgery. Eighteen patients (5.7%) were in group I and demonstrated the following risk factors for delivery within 21 days: incomplete laser surgery suspected (odds ratio [OR], 11.14; P = .0106), preoperative subchorionic hematoma (OR, 7.92, P = .0361), preoperative cervical length <2.0 cm (OR, 4.71; P = .0117), and recipient's maximum vertical pocket ≥14 cm (OR, 3.23; P = .0335). In group II, 92 of 300 patients (30.7%) delivered <32 weeks, and 25 (8.3%) delivered <28 weeks; multivariate logistic regression analyses identified 5 risk factors for delivery <32 weeks: incomplete laser surgery suspected (OR, 10.0; P = .0506); incidental septostomy (OR, 4.4; P = .0009); triplet gestation (OR, 2.6; P = .0689); postoperative membrane detachment (OR, 2.4; P = .0393); and nonposterior placental location (OR, 1.8; P = .0282).

CONCLUSION

Timing of delivery after laser for twin-twin transfusion syndrome has a bimodal distribution with distinct gestational and surgical risk factors. This information may be useful in counseling patients and in directing future avenues of research.

What-and why-the pathologist should know about twin-to-twin transfusion syndrome

Approximately 20% of all twin pregnancies are monochorionic. Between 9% and 15% of all monochorionic twin gestations are complicated by severe chronic twin-to-twin transfusion syndrome (TTTS), characterized by a gradual shift of blood volume from the donor twin to the recipient twin through placental vascular connections [1 - 3] . The prognosis of severe, untreated chronic TTTS diagnosed in midtrimester fetuses is extremely poor, with mortality rates exceeding 70% [4] . Since publication of the results of the Eurofoetus trial in 2004, laser photocoagulation of the intertwin anastomoses has become accepted as the optimal first-line therapy for severe TTTS diagnosed before 26 weeks of gestation. While laser treatment of vascular communications was initially limited to selected fetal treatment centers, its increasingly widespread use has resulted in the exposure of more pathologists, even in less specialized institutions, to laser-treated placentas. Furthermore, the surge in laser coagulation has revived the general medical, scientific, and public interest in the placental and choriovascular findings in monochorionic twin placentas. The pathologist's understanding of the pathophysiology of TTTS and of TTTS-associated placental pathology, including the findings related to laser ablation of the anastomoses, can be of great benefit to the involved obstetric/neonatal/surgical team and, ultimately, to the patients. In this review, we summarize the current knowledge of the placental contributions to TTTS and other complications of monochorionic twinning and describe the strengths and limitations of placental examination in these settings. It is our expectation that overviews such as this may serve as a template to generate consensus guidelines for standardized and evidence-based pathologic evaluation of monochorionic twin placentas.

The vascular anastomoses in monochorionic twin pregnancies and their clinical consequences

Monochorionic twin pregnancies are at increased risk of adverse outcome because of the vascular anastomoses that connect the 2 fetal circulation systems. The shared circulation is responsible for some unique complications in monochorionic twins, such as the twin-to-twin transfusion syndrome, the twin anemia polycythemia sequence, the twin reversed arterial perfusion sequence, and monoamniotic twinning. Another consequence of the shared circulation is that the well-being of one twin critically depends on that of the other. In this review, we will describe the technique of placental injection. Further, we will discuss the role of the vascular anastomoses in each of the complications described above and provide an update on their management.

Twin-twin transfusion syndrome

OBJECTIVE

We sought to review the natural history, pathophysiology, diagnosis, and treatment options for twin-twin transfusion syndrome (TTTS).

METHODS

A systematic review was performed using MEDLINE database, PubMed, EMBASE, and Cochrane Library. The search was restricted to English-language articles published from 1966 through July 2012. Priority was given to articles reporting original research, in particular randomized controlled trials, although review articles and commentaries also were consulted. Abstracts of research presented at symposia and scientific conferences were not considered adequate for inclusion in this document. Evidence reports and guidelines published by organizations or institutions such as the National Institutes of Health, Agency for Health Research and Quality, American College of Obstetricians and Gynecologists, and Society for Maternal-Fetal Medicine were also reviewed, and additional studies were located by reviewing bibliographies of identified articles. Consistent with US Preventive Task Force guidelines, references were evaluated for quality based on the highest level of evidence, and recommendations were graded accordingly.

RESULTS AND RECOMMENDATIONS

TTTS is a serious condition that can complicate 8-10% of twin pregnancies with monochorionic diamniotic (MCDA) placentation. The diagnosis of TTTS requires 2 criteria: (1) the presence of a MCDA pregnancy; and (2) the presence of oligohydramnios (defined as a maximal vertical pocket of <2 cm) in one sac, and of polyhydramnios (a maximal vertical pocket of >8 cm) in the other sac. The Quintero staging system appears to be a useful tool for describing the severity of TTTS in a standardized fashion. Serial sonographic evaluation should be considered for all twins with MCDA placentation, usually beginning at around 16 weeks and continuing about every 2 weeks until delivery. Screening for congenital heart disease is warranted in all monochorionic twins, in particular those complicated by TTTS. Extensive counseling should be provided to patients with pregnancies complicated by TTTS including natural history of the disease, as well as management options and their risks and benefits. The natural history of stage I TTTS is that more than three-fourths of cases remain stable or regress without invasive intervention, with perinatal survival of about 86%. Therefore, many patients with stage I TTTS may often be managed expectantly. The natural history of advanced (eg, stage ≥III) TTTS is bleak, with a reported perinatal loss rate of 70-100%, particularly when it presents <26 weeks. Fetoscopic laser photocoagulation of placental anastomoses is considered by most experts to be the best available approach for stages II, III, and IV TTTS in continuing pregnancies at <26 weeks, but the metaanalysis data show no significant survival benefit, and the long-term neurologic outcomes in the Eurofetus trial were not different than in nonlaser-treated controls. Even laser-treated TTTS is associated with a perinatal mortality rate of 30-50%, and a 5-20% chance of long-term neurologic handicap. Steroids for fetal maturation should be considered at 24 0/7 to 33 6/7 weeks, particularly in pregnancies complicated by stage ≥III TTTS, and those undergoing invasive interventions.

Prevalence and risk factors of cerebral lesions in neonates after laser surgery for twin-twin transfusion syndrome

OBJECTIVE

To identify risk factors for cerebral lesions among survivors of twin-twin transfusion syndrome treated with laser surgery.

STUDY DESIGN

A multilevel regression analysis examined risk factors for neonatal cerebral lesions identified by imaging. Imaging was routine in "high-risk survivors," defined as those delivered at <32 weeks' gestation, and by clinical indications if born later. Severe lesions were defined as: intraventricular hemorrhage grade III-IV, cystic periventricular leukomalacia, ventriculomegaly and/or hydrocephalus, microcephaly, infarctions, porencephalic/Dandy-Walker cysts, or bilateral other cysts.

RESULTS

For 262 consecutive laser-treated twin-twin transfusion syndrome patients, 18 neonates had severe lesions identified among 427 individual survivors (4.2%) and 242 "high-risk survivors" (7.4%). Forty-six newborns had any cerebral lesion, resulting in lesion rates of 10.8%-19.0%. Delivery <32 weeks' (odds ratio, 4.95; P < .001) and <28 weeks' (odds ratio, 6.25; P < .001) gestation were associated with increased likelihood of any cerebral lesion.

CONCLUSION

This cohort showed low rates (4-7%) of severe neonatal cerebral lesions, with prematurity being the primary risk factor.

Evolution of middle cerebral artery peak systolic velocity after a successful laser procedure for iatrogenic twin anemia-polycythemia sequence

We report a case of twin anemia-polycythemia sequence (TAPS) treated by laser at 24 + 5 weeks' gestation, 7 weeks after a first laser procedure for twin-to-twin transfusion syndrome at 16 + 6 weeks. This management led to the birth of two healthy neonates by Cesarean section at 36 weeks. In this case, weekly measurement of the middle cerebral artery peak systolic velocity allowed us to monitor the twins after both laser treatments and, more specifically, to detect TAPS. Following delivery, placental injection showed a minuscule coagulated arteriovenous anastomosis. Intrauterine transfusion is generally chosen to manage TAPS, but the choice of therapy must consider gestational age, technical difficulties and disease severity. The laser procedure cannot be used as a curative treatment for TAPS in all cases. We propose a decisional algorithm to help clinicians select the appropriate treatment.

Stage-based outcomes of 682 consecutive cases of twin-twin transfusion syndrome treated with laser surgery: the USFetus experience

OBJECTIVE

We sought to describe stage-specific perinatal outcomes after selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome.

STUDY DESIGN

Patients with twin-twin transfusion syndrome underwent SLPCV preferentially using sequential vs standard laser technique. Patient characteristics and outcome data were examined by Quintero stage.

RESULTS

Of 682 consecutive women studied, the Quintero stage distribution was: 114 stage I (17%), 177 stage II (26%), 328 stage III (48%), and 63 stage IV (9%). Perinatal survival of at least 1 twin did not differ according to stage (I-92%, II-93%, III-88%, IV-92%; P = .30). However, dual twin survival differed by stage (I-79%, II-76%, III-59%, IV-68%; P < .01), primarily because stage III pregnancies were associated with decreased donor twin survival (P < .01). Sequential SLPCV was associated with improved donor survival, independent of stage (odds ratio, 1.67; 95% confidence interval, 1.16-2.40; P < .01).

CONCLUSION

Stage-specific perinatal outcomes after laser therapy may assist physicians in patient counseling and in planning future studies.