The role of laser surgery in dissecting the etiology of absent or reverse end-diastolic velocity in the umbilical artery of the donor twin in twin-twin transfusion syndrome

Effect of Fetoscopic Laser Photocoagulation on Fetal Growth and Placental Perfusion in Twin-Twin Transfusion Syndrome

Objective: To investigate the fetal growth pattern after fetoscopic laser photocoagulation (FLP) in twin-twin transfusion syndrome (TTTS) and the effect of FLP on placental perfusion and intrauterine growth restriction (IUGR) incidence. Methods: TTTS cases with a live delivery of both twins at least 28 days after FLP and with a neonatal follow-up at our hospital at least 60 days after delivery were included. The biometric data obtained before FLP (based on ultrasound); time point M1), upon birth (M2), and at neonatal follow-up (M3) were analyzed. The body weight discordance (BWD) was defined as (estimated fetal weight [body weight] of the recipient twin − estimated fetal weight [body weight] of the donor twin)/(estimated fetal weight [body weight] of the recipient twin) × 100%. Total weight percentile (TWP) was defined as the donor + recipient twin weight percentile; the TWP indirectly reflected the total placental perfusion. Results: the BWDs decreased from M1 to M2 to M3 (24.6, 15.9, and 5.1, respectively, p < 0.001, repeated measurements). The weight percentiles of recipient twins decreased after FLP, that is, from M1 to M2 (53.4% vs. 33.6%, respectively, p < 0.001, least significant difference [LSD] test). However, the weight percentiles of donor twins increased after delivery, that is, from M2 to M3 (13.2% vs. 26.2%, respectively, p < 0.001, LSD test). Moreover, the TWPs decreased after FLP, that is, from M1 to M2 (66.2% vs. 46.8%, respectively, p = 0.002, LSD test) and increased after delivery, that is, from M2 to M3 (46.8% vs. 63.2%, respectively, p = 0.024, LSD test). The IUGR incidences in donor twins were significantly lower after FLP (77.4% vs. 56.6%, respectively, p = 0.019, McNemar test) and further decreased after delivery (56.6% vs. 37.7%, respectively, p = 0.041, McNemar Test); however, no significant difference was observed in recipient twins’ IUGR incidences among M1, M2, and M3. The donor twin had catch- up growth in body weight, height, and head circumference after delivery, and the recipient twin had catch-up growth in only body height after delivery. Conclusions: the BWD decreased after FLP in fetuses with TTTS mainly because of the decreased weight percentiles of recipient twins. Moreover, it further decreased after delivery mainly because of the increased weight percentiles of donor twins. FLP not only decreased placental perfusion but also improved the TTTS prognosis because of reduced BWD and donor twin IUGR incidence.

Association between Respiratory Distress Syndrome of Newborns and Fetal Growth Restriction Evaluated Using a Dichorionic Twin Pregnancy Model

AIMS

To evaluate the association between respiratory distress syndrome (RDS) and intrauterine fetal growth restriction (IUGR) by using a dichorionic twin model.

METHODS

We retrospectively analyzed twins delivered between September 2012 and December 2018. A dichorionic (DC) twin pregnancy with selective IUGR (sIUGR) was defined as the presence of (i) a birthweight discordance of ≥25% and (ii) a smaller twin with birth weight below the 10th percentile. Pregnancies with major fetal anomalies, delivery at gestational age below 23 weeks, and intrauterine fetal demise were excluded.

RESULTS

We included 53 DC twins with sIUGR. The sIUGR twin had a higher risk of RDS than did his appropriate for gestational age (AGA) cotwin (32.1% vs. 11.3%, p = 0.001); however, the risk of severe RDS did not significantly differ between the twins (17.0% vs 9.4%, p = 0.125). The findings of logistic regression analysis indicated that younger gestational age (weeks) at delivery (odds ratio = 0.48, p < 0.001) and IUGR (odds ratio = 13.87, p = 0.009) were significant risk factors for RDS in newborns in DC twin pregnancies with selective sIUGR.

CONCLUSIONS

IUGR was identified as a risk factor for newborn RDS. However, the association between IUGR and severe newborn RDS was not significant possibly due to the small sample size of this study.

Percent Absent End-Diastolic Velocity in the Umbilical Artery and Donor Twin Demise after Laser Surgery for Twin-Twin Transfusion Syndrome

INTRODUCTION

To examine the association of preoperative absent end-diastolic velocity (AEDV) and percent AEDV (%AEDV) in the umbilical artery (UA) with donor twin intrauterine fetal demise (IUFD) after laser surgery for twin-twin transfusion syndrome (TTTS).

METHODS

We performed a retrospective study of stage III/IV TTTS patients who underwent laser surgery from 2006 to 2016. Donors were classified as having preoperative persistent AEDV (yes/no). %AEDV was calculated for those with AEDV as 100× the proportion of the total cardiac cycle in AEDV. Using multiple logistic regression, we tested for an association between the outcome donor IUFD and AEDV risk factors (part 1) and %AEDV (part 2). We stratified these analyses by estimated fetal weight (EFW) discordance ≥20 versus <20%.

RESULTS

Of 344 cases, 153 (44.5%) donors had AEDV. Part 1 did not confirm an independent association between AEDV and donor IUFD. In the part 2 analysis of the 153 patients with AEDV, %AEDV was a positive risk factor for donor IUFD only in those with discordance (n = 129) (OR 1.04, 95% CI 1.01-1.08, p = 0.0278) when adjusting for %EFW discordance, presence of arterioarterial anastomoses, and multiparity.

DISCUSSION

Among stage III/IV TTTS patients with AEDV, %AEDV was a risk factor for donor IUFD only in the presence of EFW discordance.

Predisposing factors and neonatal outcomes for twin-twin transfusion syndrome cases developing transient donor hydrops after fetoscopic laser coagulation: a case control study

Background

Transient donor hydrops (TDH) is defined as donor hydrops developed within days after laser therapy for twin–twin transfusion syndrome (TTTS) followed by resolution later. The purpose of this study was to evaluate the incidence, neonatal outcomes and predisposing factors of post laser therapy TDH in severe TTTS.

Methods

A total of 142 patients with severe TTTS who received laser therapy were included into this study. The pre-operative characteristics and neonatal outcomes were compared between TTTS with and without post laser therapy TDH. All live neonates received cranial ultrasound examination after delivery, mild cerebral injury was defined as exhibiting at least one of the following: intraventricular hemorrhage (IVH) grade I and II, lenticulostriate vasculopathy and subependymal pseudocysts; severe cerebral injury comprised at least one among the following: IVH grade III or grade IV, cystic periventriculoleukomalacia (PVL) grade II or more, porencephalic cysts, and ventricular dilatation. Fetal survival was defined as living more than 30 days after delivery.

Results

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.

Donor catch-up growth after laser surgery for twin-twin transfusion syndrome

OBJECTIVE

To assess fetal growth after laser surgery for TTTS at the time of prenatal diagnosis, birth, and at 2years of age.

DESIGN/METHODS

Growth data were collected from surviving children treated between 2007 and 2010 as part of a study to assess neurodevelopment at 24months (±6weeks) corrected age. Fetal weights were obtained via ultrasound using Hadlock's formula at the time of preoperative assessment for laser surgery. Birth weights were recorded by the staff at the delivering institutions. Weights at 2years corrected age were recorded at the time of neurodevelopmental testing. Weights were converted into percentiles according to standard growth curves. Growth restriction was defined as <10th percentile for given age. Multilevel latent growth curve models in Mplus (twins nested in families) examined weight change over time as a function of donor status, and repeated measures ANOVA was utilized to assess in donor-recipient weight discordance over time for twin pairs.

RESULTS

99 of 206 children (56 of 130 families) were studied. There were no differences between enrolled and non-enrolled patients in donor/recipient status and survival rates, fetal demise, intrauterine growth restriction, Quintero stage, and gestational age of surgery or delivery. 48.5% were donors. The median fetal, birth, and 2-year weights for all twins were 288g, 1.9kg, and 11.8kg, respectively, and the overall prevalence of growth restriction was 28%, 22%, and 3%, respectively. Growth restriction rates at prenatal diagnosis were 56% in donors vs. 2% in recipients (OR=64.3, p<0.001); at birth, 35% vs. 10% (OR=5.0, p<0.01); and at 2years, 6% vs. 0%. Donors showed significant gains in weight percentile (B=13.1, p<0.001) and a significant decrease in growth restriction rates over time (B=-1.6, p<0.001). Weight discordance between donor and recipient pairs also significantly decreased over time (linear F(1,42)=54.34, p<0.001).

CONCLUSIONS

After laser surgery for TTTS, donor twins exhibit significant catch-up growth by two years of age.

Ultrasound prognostic factors after laser surgery for twin-twin transfusion syndrome to predict survival at 6 months

OBJECTIVE

To evaluate the significance of ultrasound findings, detected one or two weeks after laser surgery for twin-twin transfusion syndrome, in predicting the mortality at 6 months of age.

METHODS

Ultrasound evaluation including fetal biometry, amniotic fluid volume estimation and Doppler examination was performed between 7 and 14 days after surgery for 181 cases. The presence of one or more effusions and single fetal death were also determined. Associations between ultrasound findings and mortality at 6 months of age were evaluated using multiple logistic regression analysis.

RESULTS

Of the total 181 pairs, 145 (80.1%) donor and 160 (88.1%) recipient twins survived in utero for more than 7 days after surgery, and hence were included in the analysis. The survival rate at 6 months was 66.9% for the donor and 80.7% for the recipient twins. Risk factors for death in the donor were the presence of severe intrauterine growth restriction and effusions. In recipients, elevation in the middle cerebral artery peak systolic velocity coincided with fetal death, but this occurred in only three cases.

CONCLUSION

Ultrasound risk factors one week after surgery included severe intrauterine growth restrictions and effusions in the donor twins.

Sequential selective laser photocoagulation of communicating vessels in twin–twin transfusion syndrome

OBJECTIVE

We have previously described the selective laser photocoagulation of communicating vessels (SLPCV) technique for the treatment of twin-twin transfusion syndrome (TTTS). Because TTTS is thought to result from a net transfer of blood from the donor twin to the recipient twin, we hypothesized that lasering the arteriovenous anastomoses from the donor to the recipient (AVDRs) first (sequential SLPCV or SQLPCV) would result in an improved hemodynamic status and decreased likelihood of intrauterine fetal demise of the donor twin (IUFD-D).

MATERIALS AND METHODS

The diagnosis of TTTS was made by ultrasound showing the combined presence of a maximum vertical pocket > or = 8 cm in one sac and < or =2 cm in the other in a monochorionic/diamniotic twin pregnancy. Triplet pregnancies and monoamniotic pregnancies were excluded. Severity of TTTS was assessed using the Quintero staging system. All vascular anastomoses were endoscopically identified and classified as AVDR (AV from donor to recipient), AVRD (AV from recipient to donor), arterio-arterial (AA), or veno-venous (VV). The surgical procedure was coded as SQLPCV if all AVDRs were lasered first. Outcome measures included intrauterine fetal demise and perinatal survival.

RESULTS

One hundred and ninety-three TTTS patients (137 SQLPCV, 56 SLPCV) underwent surgery from May 2003 to August 2005. Gestational age at surgery or at delivery, Stage, patent anastomoses, or persistent/reverse TTTS were not different between the groups. IUFD-D was significantly lower in the SQLPCV than in the SLPCV group (7.3% vs 21.4%, respectively, p = 0.005). Dual perinatal survival was significantly higher in the SQLPCV than in the SLPCV group (73.7% vs 57.1%, respectively, p = 0.02), although the incidence of at least one survivor was not different between the groups (90.5% vs 87.5%, respectively). Logistic regression showed SQLPCV, but not placental location, operating time or number of anastomoses to be significantly associated with a decreased likelihood of IUFD-D (p = 0.007).

CONCLUSION

SQLPCV is associated with a decreased likelihood of IUFD-D and an increased rate of dual survivors compared to SLPCV. SQLPCV represents both an anatomical and functional surgical approach to the laser treatment of twin-twin transfusion syndrome.

Validation of Quintero stage III sub-classification for twin-twin transfusion syndrome based on visibility of donor bladder: characteristic differences in pathophysiology and prognosis

OBJECTIVE

To validate the Quintero stage III subclassification for twin-twin transfusion syndrome (TTTS) based on visibility of the bladder of the donor twin.

METHODS

Between July 2002 and August 2006, there were 131 pregnant Japanese women affected by severe TTTS before 26 weeks' gestation, treated with fetoscopic laser surgery at five centers in Japan, whose pregnancies continued beyond 22 weeks. Outcome data were available in all cases and surviving infants were followed up for at least 6 years. This study focused on the Stage III TTTS patients. These were subclassified into Stage III atypical (abnormal Doppler flow with visible donor bladder) and Stage III classical (abnormal Doppler flow with non-visible donor bladder) groups. Perioperative data and postnatal outcomes were compared between the groups.

RESULTS

Seven Stage I, 22 Stage II, 82 Stage III and 20 Stage IV pregnancies continued beyond 22 weeks. There was a significantly higher incidence of absent or reversed end-diastolic velocity in the umbilical artery (UA-AREDV) of the donor in Stage III atypical than in Stage III classical patients (83.8% vs. 53.3%, P = 0.004). Stage III atypical cases also had a significantly higher incidence of arterioarterial (AA) anastomoses (72.9% vs. 17.8%, P < 0.001) and intrauterine fetal demise (IUFD) of the donor (43.2% vs. 13.3%, P = 0.002). However, there were no differences in overall survival or in abnormal brain scans of surviving infants. Donors with both UA-AREDV and AA anastomoses had a significantly higher incidence of IUFD compared with the others (53.3%, P < 0.001).

CONCLUSIONS

Quintero stage III atypical was characterized by a high incidence of AA anastomoses and UA-AREDV of the donor, resulting in IUFD. Subclassification of Stage III based on visibility of the bladder of the donor twin was adequate for and compatible with differentiating prognosis and pathophysiology.

Fetal growth after laser therapy for twin-twin transfusion syndrome

OBJECTIVE

The objective of the study was to compare twin weight discordance and prevalence of intrauterine growth restriction (IUGR) before laser therapy and after birth in pregnancies complicated by twin-twin transfusion syndrome (TTTS).

STUDY DESIGN

Women with TTTS who underwent laser therapy with dual neonatal survivors born at least 28 days after surgery were studied. Estimated fetal weight (EFW) discordance at the preoperative sonogram and birthweight (BW) discordance were calculated. Weights below gestational age-corrected 10th percentile at sonogram and at birth for each twin were designated as IUGR.

RESULTS

Among 211 women studied, the mean EFW discordance measured 26.6% and mean BW discordance was 18.4%, yielding a mean 8.2% decrease in weight discordance (P < .001). Comparing IUGR diagnoses before surgery and at birth, the recipient's proportion was unchanged (9.5% vs 7.1%, P = .353), whereas the donor's proportion decreased (64.5% vs 28.9%, P < .001).

CONCLUSION

Twin weight discordance and donor fetus IUGR appear to improve after laser therapy for TTTS.

The individual fetal weight/estimated placental weight ratios in monochorionic twins with selective intrauterine growth restriction

OBJECTIVES

To evaluate the individual fetal weight/estimated placental weight ratios (F/P ratio) of the two fetuses in monochorionic (MC) twins with selective intrauterine growth restriction (IUGR).

MATERIAL AND METHODS

MC twin with selective IUGR was defined as an estimated fetal weight below the 10th percentile in one twin of MC pregnancy. The estimated individual placental weight was obtained by cutting the placenta along the vascular equator into two territories. A total of 15 MC twins with selective IUGR and 18 MC twins without selective IUGR were included in this study.

RESULTS

The individual F/P ratio in the IUGR twin is significantly higher than that in the appropriate for gestational age (AGA) one in MC twin with selective IUGR (6.4 vs 4.0 respectively, p < 0.001). In MC twin without IUGR, the F/P ratios are not significantly different between the two fetuses (5.4 vs 5.1, respectively).

CONCLUSION

The high F/P ratio in the IUGR twin in MC with selective IUGR may be due to the placental reserve phenomenon, so that a smaller placental territory may suffice to perfuse the IUGR twin. In other words, in MC twin gestations with an IUGR twin, the fetal weights are not proportional to the placental masses.

Laser therapy and serial amnioreduction as treatment for twin-twin transfusion syndrome: a metaanalysis and review of literature

OBJECTIVE

The objective of the study was to review current controversy on laser therapy (LT) vs serial amnioreduction (SA) performed for twin-twin transfusion syndrome (TTTS).

STUDY DESIGN

A search in PubMed from 1997-2007 was performed. Inclusion criteria were diamniotic monochorionic pregnancy, TTTS diagnosed with standard parameters, and peri- and neonatal outcomes well defined. Triplets and investigations on other topics of TTTS rather than perinatal outcomes were excluded. A metaanalysis was performed by fixed-effect model (heterogeneity <25%).

RESULTS

Ten articles provided 611 cases of TTTS (LT: 70%; SA: 30%) and included 4 studies comparing the 2 treatments (395 cases: LT, 58%; SA, 42%). Fetuses undergoing LT were more likely to survive than fetuses undergoing SA (overall survival rate: P < .0001; odds ratio [OR], 2.04; 95% confidence interval [CI], 1.52-2.76; neonatal death: P < .0001; OR, 0.24; 95% CI, 0.15-0.40; neurologic morbidity: P < .0001; OR, 0.20; 95% CI, 0.12-0.33).

CONCLUSION

This metaanalysis shows that LT is associated with better outcomes than SA and proposes new topics for future research.

Mise en évidence des anastomoses vasculaires par la vélocimétrie doppler dans les grossesses gémellaires monochoriales. Revue de la littérature à propos de trois cas

Three cases of intermittent absent end-diastolic and reversed end-diastolic flow velocity (A/REDV) are reported in the proximal umbilical artery of the growth-retarded twin in monochorionic twin pregnancies. This typical doppler velocimetric pattern has been related to arterio-arterial anastomoses in two cases of intra-uterine growth retardation and in one case of twin-twin transfusion syndrome. According to the literature, superficial arterio-arterial anastomoses may be detected by doppler colour velocimetry in 75 to 85% of cases, while identification of arteriovenous connections is more difficult to be documented in vivo (50% of cases in experienced hands). The role of superficial vascular anastomoses, either arterio-arterial or venovenous, and that of deep arteriovenous communications is now well documented in the main complications of monochorionic pregnancies, particularly for twin-twin transfusion syndrome, intrauterine growth retardation, intrauterine fetal death and acardiac twins.

Percent absent end-diastolic velocity in the umbilical artery waveform as a predictor of intrauterine fetal demise of the donor twin after selective laser photocoagulation of communicating vessels in twin-twin transfusion syndrome

OBJECTIVE

Absent end-diastolic velocity (AEDV) in the umbilical artery of the donor twin is a known risk factor for intrauterine fetal demise (IUFD) of this fetus after selective laser photocoagulation of communicating vessels (SLPCV) for twin-twin transfusion syndrome (TTTS). The aim of this study was to assess the proportion of time, expressed as a percentage, of the cardiac cycle spent in AEDV (%AEDV) as a predictor of IUFD of the donor.

METHODS

All patients referred for possible SLPCV underwent complete preoperative staging evaluation including Doppler assessment of the umbilical artery. %AEDV was calculated retrospectively as 100 x (time of the cycle spent in AEDV divided by duration of total cardiac cycle). Patients without AEDV were considered to have a %AEDV of 0. Follow-up Doppler studies were performed 16-24 h after SLPCV. IUFD of the donor was recorded if the donor twin died any time prior to delivery.

RESULTS

Of 401 patients undergoing SLPCV, 127 had AEDV. Preoperative AEDV of the donor twin was associated with an increased risk of IUFD of the donor (40.9% vs. 14.2%, P < 0.0001). %AEDV was measured in 72/127 (56.7%) donors with AEDV for whom digital images were available. Within these 72 patients, the mean %AEDV was significantly higher in patients with IUFD of the donor (36.5% vs. 29.6%, P = 0.01). IUFD of the donor was similar in patients with AEDV, regardless of whether %AEDV was measured (36% vs. 47%, P = 0.2). A %AEDV > 30 was associated with a 4.3-fold increase in the risk of IUFD of the donor (95% CI, 1.4-12.7), a sensitivity of 77% and a negative predictive value of 81.3%. Logistic regression showed that %AEDV, but not number of anastomoses, placental location, presence of artery-to-artery anastomoses or the presence or absence of EDV was associated significantly with IUFD of the donor.

CONCLUSION

%AEDV is a novel Doppler parameter in the assessment of patients with TTTS. %AEDV, rather than AEDV alone, is a significant risk factor for IUFD of the donor twin and %AEDV > 30 is associated with an increased risk of IUFD of the donor in TTTS patients treated with SLPCV. Assessment of %AEDV should be considered part of the preoperative evaluation of TTTS patients.

Fetoscopic laser therapy for twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) complicates approximately 1 in 5 of all monochorionic, diamniotic twin pregnancies. If of early onset and untreated, severe TTTS is associated with a dismal prognosis, with perinatal mortality rates exceeding 90%. The most controversial issue regarding the optimal treatment of TTTS has centered on the use of amniocentesis or laser until the first and only randomized trial on interventions for TTTS was published a couple of years ago, comparing laser to amnioreduction. That report confirmed that the laser group had a higher likelihood of the survival of at least one twin to 28 days of age and to 6 months of age. Infants in the laser group also had a lower incidence of cystic periventricular leukomalacia and were more likely to be free of neurologic complications at 6 months of age (52% vs. 31%, p = 0.003). Although not every case of TTTS is an eligible candidate for fetoscopic-guided laser therapy, it is recommended that obstetricians who have the chance to manage TTTS in their daily practice be familiar with the rationale behind this laser treatment for TTTS.