Twin-twin transfusion syndrome: a frequently missed diagnosis with important consequences

Long-Term Neurodevelopmental Outcome After Selective Fetoscopic Laser Therapy for Stage I Twin-Twin Transfusion Syndrome

Twin-twin transfusion syndrome (TTTS) is a serious complication in monochorionic (MC) pregnancies. Fetoscopic laser surgery (FLS) is the primary treatment for advanced TTTS, but managing Quintero stage I TTTS is still controversial. We conducted an observational study evaluating the 2-year neurodevelopment of fetuses, which underwent FLS for stage I TTTS, compared with advanced TTTS and uncomplicated monochorionic diamniotic twins (MCDTs). The study included 156 children: 14 in stage I TTTS group, 28 in advanced TTTS group, and 114 in uncomplicated twin group. In stage I TTTS, 92.9% showed normal neurodevelopment, with no severe neurological impairments observed. These results were comparable with uncomplicated twins (92.1% normal neurodevelopment, P = .921, adjusted odds ratio [aOR] = 1.56, 95% confidence interval [CI] = 0.42-5.79; 1.8% severe impairment, P = .617). Advanced TTTS had a non-significant lower rate of normal neurodevelopment (89.3%, P = .710, aOR = 1.31, 95% CI = 0.12-14.87). In conclusion, FLS for stage I TTTS shows favorable long-term neurodevelopmental outcomes, similar to uncomplicated MC pregnancies.

Noninvasive Evaluation of Fetal Zygosity in Twin Pregnancies Involving a Binary Analysis of Single-Nucleotide Polymorphisms

Twin pregnancy constitutes significant risks for maternal and fetal health, which is usually detected by ultrasound examination at early gestation. However, the imaging-based approach may not accurately identify all twins confounded by practical or clinical variables. The analysis of fetal cell-free DNA in noninvasive prenatal screening assays can completement the ultrasound method for twin detection, which differentiates fraternal or identical twins based on their distinct genotypes. Here, a new noninvasive prenatal screening employing high-coverage next-generation sequencing for targeted nucleotide polymorphisms was developed for detection of zygosity and determination of fetal fraction in twin pregnancies. This method utilizes a binary analysis of both the number and allelic fraction of fetus-specific single-nucleotide polymorphisms to infer the zygosity. In 323 samples collected from 215 singleton, 90 dizygotic, and 18 monozygotic twin pregnancies, all 90 dizygotic twins were correctly detected, with a 100% sensitivity and a 100% specificity. In addition, this method can detect complex pregnancies, such as egg donors, contamination, and twins with complete hydatidiform mole. The fetus-specific fetal fraction change was monitored in nine dizygotic twin pregnancies, which demonstrated highly variable dynamics of fetal cell-free DNA turnover up to 7 weeks after twin reduction. Overall, this study provides a new noninvasive prenatal screening strategy for the accurate identification of twin zygosity and quantification of fetal fraction, which has important clinical implications for the management of twin pregnancies.

Comparison of renal artery Doppler parameters of monochorionic diamniotic twin pregnancies with and without twin-to-twin transfusion syndrome

Background

Monochorionic diamniotic (MCDA) twin pregnancies are considered high-risk for several reasons, especially the risk of twin-to-twin transfusion syndrome (TTTS). Renal artery Doppler (RAD) is reported as a useful tool for predicting oligohydramnios in singleton pregnancies. We aimed to compare the RAD indices between MCDA twins with and without TTTS.

Materials and Methods

In this case-control study, all pregnant women aged 18-38 years, with gestational age ≥ 18 weeks, who were referred to two Prenatal Clinics, Alzahra and Beheshti Educational Hospitals, affiliated to Isfahan University of Medical Sciences, Isfahan, Iran, October 2020-March 2022 were enrolled; the women with MCDA twin pregnancies complicated by TTTS (case group, n = 12) and without TTTS (control group, n = 24). For each twin, biometric analysis, fetal weight, and Doppler study of fetal arteries, including RAD, middle cerebral artery (MCA), umbilical artery, and ductus venosus were performed. Peak systolic velocity, Pulsatility index (PI), resistance index (RI), and systole/diastole (S/D) were measured for all arteries.

Results

The donors of the case group had a lower mean MCA S/D (4.48 ± 1.89) than the control group (6.48 ± 1.97) (P = 0.01) and higher mean umbilical parameters, including PI, RI, and S/D (P < 0.05). The recipients of the case group had a lower mean renal PI than the control (P = 0.008) and lower mean MCA PI, RI, and S/D (P < 0.05). The donor group had a higher mean umbilical RI and S/D than the recipient twin, while the mean fetal weight of the recipient group was higher (P < 0.05).

Conclusion

Comparing the RAD parameters between the twins with and without TTTS in the present study did not identify significant results, which rejected the primary hypothesis. Among all RAD parameters, the only significant difference observed in the present study was the lower RAD PI in RT, which cannot suggest this measurement as a valuable tool for the prediction of TTTS in MCDA twins. Therefore, the results of the present study failed to show the additional value of RAD, compared with the conventional Doppler examination of fetal arteries. Further studies are required to prove this conclusion.

Patient-Reported Monochorionic-Diamniotic Twin Pregnancy Management and Experiences During the COVID-19 Pandemic: A Mixed-Methods Cross-Sectional Survey

Monochorionic-diamniotic (MCDA) pregnancies are high-risk necessitating ongoing screening for serious complications and quick decision-making. COVID-19 pandemic protocols introduced unique challenges to pregnancy management and patient experience. In late 2021, an online, mixed-methods, cross-sectional survey recruited 561 participants who experienced an MCDA pregnancy within five years. Analyses included descriptive and bivariate statistics and thematic analysis. Findings suggest the pandemic did not negatively affect screening/diagnosis for these participants. Care consistent with guidelines was received by most, with care slightly better during the pandemic. Almost 80% (79.0%) received an MCDA diagnosis by gestational week 14 before the pandemic, 87.8% during. Most received biweekly ultrasounds, 88.0% prior to the pandemic, 88.9% during. Experiences were affected in other ways for almost 44% of participants pregnant during COVID-19; in ways likely shared by other high-risk pregnancies. Thematic analysis revealed management during COVID-19 impacted self-advocacy and emotions (eg, alienation, anxiety), made care seem impersonal, and resulted in delayed or canceled appointments. Policies should be considered, so future healthcare disruptions do not impact patients and preserve in-person health care with access to a support person.

Clinician-reported Chorionicity and Zygosity Assignment using single-nucleotide polymorphism-based cell-free DNA Lessons learned from 55,344 Twin Pregnancies

Objective

Prenatal chorionicity assessment relies on ultrasound, which can be confounded by many factors. Noninvasive assessment of zygosity is possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA testing. Our objective was to determine the relationship between provider‐reported chorionicity and SNP‐cfDNA assignment of twin zygosity.

Methods

All twin pregnancy blood samples received by a reference laboratory between September 27, 2017 and September 8, 2021 were included. Chorionicity assignment was requested on the requisition, recorded as; monochorionic (MC), dichorionic, or “don't know”. SNP‐cfDNA zygosity results, monozygotic (MZ) or dizygotic (DZ), were correlated with chorionicity assignment.

Results

59,471 twin samples (median gestational age = 12.0 weeks at draw) were received and analyzed; 55,344 (93.1%) received zygosity assignment. SNP‐cfDNA reported 16,673 (30.1%) MZ and 38,671 (69.9%) as DZ. Provider‐reported chorionicity was compared to the zygosity assignment for each case. Of 6283 provider‐reported MC twins, 318 (5.1%) were reported as DZ using SNP‐cfDNA.

Conclusion(s)

One in 20 suspected MC twin pregnancies were reported as DZ using SNP‐cfDNA. Approximately 30% of 55,344 twin pregnancies were found to be MZ, including cases where chorionicity was unknown. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

What's already known about the topic?

The assignment of chorionicity early in pregnancy can improve perinatal outcomes of twin pregnancies. Prenatal assessment of chorionicity relies on ultrasound (US), and the accuracy of US can be confounded by many factors, including gestational age (GA) and operator experience. Noninvasive assessment of zygosity is now possible using single nucleotide polymorphism (SNP)‐based cell‐free DNA (cfDNA).

What does this study add?

This is the first population‐based study describing the correlation between cfDNA assessment of zygosity and chorionicity. In 55,344 twin pregnancies, approximately 30% were found to be monozygotic (MZ), including cases where chorionicity was unknown. We found that one in 20 suspected monochorionic (MC) twin pregnancies were reported as dizygotic (DZ) twins (DZ) by SNP‐cfDNA testing. SNP‐cfDNA zygosity assessment is a useful adjunct assessment for twin pregnancies, particularly those reported as MC or without determined chorionicity.

Monochorionic monoamniotic twin pregnancies

Monoamniotic twin pregnancies are rare, but early diagnosis of such pregnancies is critical, as the incidence of complications in these pregnancies is much higher than in diamniotic or dichorionic twin pregnancies. Overall, only 70% of all monoamniotic twins will survive. Furthermore, approximately half of fetal deaths in these pregnancies are because of the high incidence of fetal anomalies (15%-25%), such as twin reversed arterial perfusion sequence and conjoined twinning. Therefore, early anatomy screening in the first trimester of pregnancy is recommended. Other causes of fetal death in these pregnancies include twin-twin transfusion syndrome, tight cord entanglement, or acute hemodynamic imbalances through the large placental vascular anastomoses. After viability, fetal surveillance can be intensified, as this decreases the risk of in utero death. Both inpatient and outpatient surveillance are reasonable. If otherwise uncomplicated, monoamniotic twins should be delivered at 33 to 34 weeks' gestation. Most centers will deliver by cesarean delivery, but some continue to advocate for vaginal delivery. Lastly, neonatal morbidity is high in monoamniotic twin pregnancies and is mainly related to prematurity.

Non-invasive prenatal testing in the management of twin pregnancies

Twin pregnancies are common and associated with pregnancy complications and adverse outcomes. Prenatal clinical management is intensive and has been hampered by inferior screening and less acceptable invasive testing. For aneuploidy screening, meta‐analyses show that non‐invasive prenatal testing (NIPT) through analysis of cell‐free DNA (cf‐DNA) is superior to serum and ultrasound‐based tests. The positive predictive value for NIPT is driven strongly by the discriminatory power of the assay and only secondarily by the prior risk. Uncertainties in a priori risks for aneuploidies in twin pregnancies are therefore of lesser importance with NIPT. Additional information on zygosity can be obtained using NIPT. Establishing zygosity can be helpful when chorionicity was not reliably established early in pregnancy or where the there is a concern for one versus two affected fetuses. In dizygotic twin pregnancies, individual fetal fractions can be measured to ensure that both values are satisfactory. Vanishing twins can be identified by NIPT. Although clinical utility of routinely detecting vanishing twins has not yet been demonstrated, there are individual cases where cf‐DNA analysis could be helpful in explaining unusual clinical or laboratory observations. We conclude that cf‐DNA analysis and ultrasound have synergistic roles in the management of multiple gestational pregnancies.

What's already known about this topic?

In singleton pregnancies, non‐invasive prenatal testing (NIPT) for fetal aneuploidy is more effective than conventional serum and ultrasound‐based screening tests.

NIPT is more complex in dizygotic twin pregnancies due to the presence of two fetal genotypes.

Overall fetal fraction is higher in twin pregnancies but the individual contribution for each fetus is lower.

What does this study add?

A review of cell‐free DNA testing in twin pregnancies.

Individual fetal fractions in dizygotic twin pregnancies can be measured.

Zygosity can be established using NIPT and this can be particularly useful when there are concerns about chorionicity or determining whether one versus two fetuses are affected.

Vanishing twins can be detected through NIPT and this testing could be considered for some apparently singleton pregnancies with complications.

Twin to twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a common complication that typically presents in the second trimester of pregnancy in 10-15% of monochorionic twins due to net transfer of volume and hormonal substances from one twin to the other across vascular anastomoses on the placenta. Without recognition and treatment, TTTS is the greatest contributor to fetal loss prior to viability in 90-100% of advanced cases. Ultrasound diagnosis of monochorionicity is most reliable in the first trimester and sets the monitoring strategy for this type of twins. The diagnosis of TTTS is made by ultrasound with the findings of polyhydramnios due to volume overload and polyuria in one twin and oligohydramnios due to oliguria of the co-twin. Assessment of bladder filling as well as arterial and venous Doppler patterns are required for staging disease severity. Assessment of fetal cardiac function also provides additional insight into the fetal cardiovascular impacts of the disease as well as help identify fetuses that may require postnatal follow up. Fetoscopic laser ablation of the communicating vascular anastomoses between the twins is the standard treatment for TTTS. It aims to cure the condition by interrupting the link between their circulations and making them independent of one another. Contemporary outcome data after laser surgery suggests survival for both fetuses can be anticipated in up to 65% of cases and survival of a single fetus in up to 88% of cases. However, preterm birth remains a significant contributor to postnatal morbidity and mortality. Long term outcomes of TTTS survivors indicate that up to 11% of children may show signs of neurologic impairment. Strategies to minimize preterm birth after treatment and standardized reporting by laser centers are important considerations to improve overall outcomes and understand the long-term impacts of TTTS.

Long-Term Outcome of Monochorionic Twins after Fetoscopic Laser Therapy Compared to Matched Dichorionic Twins

INTRODUCTION

The only causal therapy is fetoscopic laser surgery (FLS). The aims of this study were to analyze the long-term outcome of monochorionic twins treated by FLS, including their school career, need for therapy and special aid equipment, and free-time activities, and compare their outcome to matched dichorionic twins.

MATERIAL AND METHODS

Among the 57 women treated at a single fetal treatment center between 2008 and 2017 with FLS because of twin-to-twin transfusion syndrome, 25 women with 42 children were included in the FLS group. The control group consisted of 16 dichorionic twin pairs matched for birth year, gestational age (GA), birth weight, and sex. The long-term outcome was assessed by a parental questionnaire and a standardized neurodevelopmental examination for children born before 32 gestational weeks or with a birth weight lower than 1500 g. They were also registered into the Swiss Neonatal Network database. The primary outcome was event-free survival, defined as normal neurology, behavior, vision, and hearing. The secondary outcomes were school career, need for therapy and special aid equipment, and free-time activities.

RESULTS

An event-free survival was found in 32 children (76%) in the laser and in 24 children (75%) in the control group (p = 0.91). Neurological anomalies were found in 5 children (12%) in the laser group and 3 children (9%) in the control group (p = 1.00). Multiple logistic regression analysis showed that GA at delivery was the only predictive factor for event-free survival. There were no significant differences regarding school career, therapies, or special aid equipment between the 2 groups. We found that children without FLS were involved in more free-time activities and needed fewer breaks during physical activity than children with FLS during pregnancy.

CONCLUSION

The outcome of monochorionic twins treated with FLS is comparable to the outcome of dichorionic twins. Long-term neurodevelopment in the cohort was mainly dependent on GA at birth.

Outcome after fetoscopic laser coagulation in twin-twin transfusion syndrome - is the survival rate of at least one child at 6 months of age dependent on preoperative cervical length and preterm prelabour rupture of fetal membranes?

Purpose: Twin-to-twin transfusion syndrome (TTTS) complicates 10-15% of all monochorionic twin pregnancies. Selective laser coagulation of placental anastomoses is the only causal therapy. The aim of this study was to analyze the neonatal survival, the survival rate of at least one child at 6 months of age, and maternal outcome after laser therapy in a Swiss cohort.Material and methods: Between 2008 and 2014, 39 women were treated with fetoscopic laser procedure due to TTTS. Two women were excluded from the study because of missing informed consent or loss of follow-up. The women were divided into two groups: group 1 with a cervical length >25 mm and group 2 with a cervical length ≤25 mm. The primary end point was the survival rate of at least one child at 6 months of age and its dependence on maternal preoperative cervical length or the time interval between operation (OP)-preterm prelabour rupture of fetal membranes (PPROM). Secondary outcomes were neonatal complications and maternal complications due to the procedure. Statistical analysis was performed using the program SPSS 22. A p-value of <.05 was considered statistically significant.Results: Mean gestational age (GA) at OP of group 1 (20.3 ± 3 GW) was comparable with group 2 (21.5 ± 2.4 GW; p = .27). The GA at birth was significantly higher in group 1 (31.5 ± 5.9 GW) than in group 2 (27.0 ± 4.7 GW: p = .02). The survival rate of at least one child at 30 days and 6 months of age was 81% in group 1 and only 60% in group 2 (p = .1). PPROM <32 GW occurred in 43%. The survival rate of at least one child was significantly higher if the OP-PPROM interval was >28 days (93 versus 43%; p = .02). Major brain injury was observed in 11% of infants. Severe maternal complications (pulmonary edema) occurred in three cases (8%).Conclusions: Our survival rate of at least one child at 30 days and 6 months of age and the outcome of the mothers is well comparable to other international studies. A preoperative maternal cervical length of >25 mm and an occurrence of PPROM more than 28 days after the laser therapy is associated with a higher survival rate of at least one child at 6 months of age.

Twin-Twin Transfusion Syndrome and Maternal Symptomatology-An Exploratory Analysis of Patient Experiences When Reporting Complaints

Objective:

The aim of this study was to assess patient experiences when reporting symptoms of twin–twin transfusion syndrome (TTTS) to their health-care providers.

Methodology:

The study utilized an online, retrospective survey of women, over the age of 18, who were living in the United States at the time of their pregnancy and had completed a TTTS pregnancy.

Results:

Three hundred sixty-seven cases were included for analysis. Nearly half of the respondents (45.2%) reported experiencing maternal symptoms prior to TTTS diagnosis. The average number of symptoms experienced was 2.85. The average gestational week of symptom onset was 18.2. A total of 76.2% of respondents experiencing symptoms shared these concerns with their health-care provider; however, slightly more than half (51.2%) believed that the provider dismissed their complaints.

Conclusions:

Results suggest a disconnect between patients’ reporting TTTS symptoms and health-care providers responding attentively, as perceived by the patient. It would be advantageous for health-care providers to inform women pregnant with a monochorionic–diamniotic pregnancy to immediately report the presence of any symptom described in the present research, which may be associated with any number of twin pregnancy–related complications.

Regimens of ultrasound surveillance for twin pregnancies for improving outcomes

BACKGROUND

Increased ultrasound surveillance of twin pregnancies has become accepted practice due to the higher risk of complications. There is no current consensus however as to the method and frequency of ultrasound monitoring that constitutes optimal care.

OBJECTIVES

To systematically review the effects of different types and frequency of ultrasound surveillance for women with a twin pregnancy on neonatal, fetal and maternal outcomes.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register, ClinicalTrials.gov, the WHO International Clinical Trials Registry Platform (ICTRP) (all searched 11 August 2017), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised and quasi-randomised trials (including those published in abstract form) comparing the effects of described antenatal ultrasound surveillance regimens in twin pregnancies. Trials using a cluster-randomised design would have been eligible for inclusion in this review but none were identified. Trials using a cross-over design are not eligible for inclusion in this review.Different types and frequencies of ultrasound testing (for fetal surveillance and detection of specific problems) compared with each other and also compared with no testing. For example, an intervention might comprise a specific approach to ultrasound examination with dedicated components to detect twin-specific pathology. Different interventions could also include a specific type of surveillance at different intervals or different combinations at the same intervals.In this review we only found one study looking at fetal growth (biometry) and Doppler ultrasounds at 25, 30 and 35 weeks' gestation versus fetal growth alone.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and quality, and extracted data. We checked data for accuracy.

MAIN RESULTS

We included one trial of 526 women with a twin pregnancy of two viable twins, with no known morphological abnormality, in this review. The trial compared women receiving fetal growth and Doppler ultrasounds at 25, 30 and 35 weeks' gestation to fetal growth alone. We judged the included study to be at low risk of bias however the risk of performance and detection bias were unclear.The primary outcome was the perinatal mortality rate (after randomisation), for which there was no evidence of a clear difference between the fetal growth + Doppler and the fetal growth alone groups (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.32 to 2.41, low-quality evidence) with similar rates in both groups (seven events in the Dopper + fetal growth group and eight in the fetal growth alone group). No clear differences were seen between the two regimens for the other outcomes in this review: stillbirth (RR 0.67, 95% CI 0.11 to 3.99), neonatal death (RR 1.01, 95% CI 0.29 to 3.46, low-quality evidence), gestational age at birth (weeks) (mean difference 0.10, 95% CI -0.39 to 0.59, moderate-quality evidence), infant requiring ventilation (RR 0.86, 95% CI 0.59 to 1.25), admission to special care or intensive care units (RR 0.96, 95% CI 0.88 to 1.05), caesarean section (any) (RR 1.00, 95% CI 0.81 to 1.23, high-quality evidence), elective caesarean section (RR 1.06, 95% CI 0.77 to 1.47), emergency caesarean section (RR 0.93, 95% CI 0.66 to 1.32), induction of labour (RR 1.10, 95% CI 0.80 to 1.50, moderate-quality evidence) or antenatal hospital admission (RR 0.96, 95% CI 0.80 to 1.15, high-quality evidence). The number of preterm births before 28 weeks' gestation was not reported in the included study. For the mortality-related outcomes, event numbers were small.The included study did not report the majority of our maternal and infant secondary outcomes. Infant outcomes not reported included fetal acidosis, Apgar scores less than 7 at five minutes and preterm birth before 37 and 34 weeks' gestation. The maternal outcomes; length of antenatal hospital stay, timely diagnosis of significant complications, rate of preterm, prelabour rupture of membranes and women's level of satisfaction with their care were not reported. The study did not classify twin pregnancies according to their chorionicity. An awareness of the chorionicity may have improved applicability of this data set.We downgraded outcomes assessed using GRADE for imprecision of effect estimates.

AUTHORS' CONCLUSIONS

This review is based on one small study which was underpowered for detection of rare outcomes such as perinatal mortality, stillbirth and neonatal death.There is insufficient evidence from randomised controlled trials to inform best practice for fetal ultrasound surveillance regimens when caring for women with a twin pregnancy. More studies are needed to evaluate the effects of currently used ultrasound surveillance regimens in twin pregnancies. Future research could report on the important maternal and infant outcomes as listed in this review.

Identifying families' shared disease experiences through a qualitative analysis of online twin-to-twin transfusion syndrome stories

Background

Twin-to-twin transfusion syndrome (TTTS) affects 10–20 % of monochorionic diamniotic (MCDA) births and accounts for 50 % of fetal loss in MCDA pregnancies. This exploratory qualitative study identified shared experiences, including potential emotional and psychosocial impacts, of this serious disease.

Methods

Forty-five publicly accessible, online stories posted by families who experienced TTTS were analyzed using grounded theory.

Results

Shared TTTS experiences included a common trajectory: early pregnancy experiences, diagnostic experiences, making decisions, interventions and variable outcomes. Families vacillated between emotional highs such as joy, excitement and relief, and lows including depression, anxiety, anger and grief.

Conclusions

TTTS disease experience can be considered an “emotional roller coaster” exacerbated by TTTS’s unpredictable and quickly changing nature with the potential for emotional and psychosocial effects. Increased TTTS awareness and research about its corresponding impacts can ensure appropriate patient and family support at all phases of the TTTS experience.

Cardiac Manifestations of Twin–to–Twin Transfusion Syndrome

This review addresses the physiology of monochorionic diamniotic (MC/DA) twins and the potential for twin–twin transfusion syndrome (TTTS). It focuses on the underlying cardiovascular pathophysiology of TTTS and the cardiovascular impact of TTTS for both the recipient and the donor twin. It explains the principles for assessment and monitoring of these cardiovascular changes and how these may be used to guide pregnancy management. Finally, it describes the effect of treatment on the altered hemodynamics and how this can influence pregnancy and perinatal management, as well as longer-term follow-up.

Simulator training in fetoscopic laser surgery for twin-twin transfusion syndrome: a pilot randomized controlled trial

OBJECTIVE

To evaluate the effect of a newly developed training curriculum on the performance of fetoscopic laser surgery for twin-twin transfusion syndrome (TTTS) using an advanced high-fidelity simulator model.

METHODS

Ten novices were randomized to receive verbal instructions and either skills training using the simulator (study group; n = 5) or no training (control group; n = 5). Both groups were evaluated with a pre-training and post-training test on the simulator. Performance was assessed by two independent observers and comprised a 52-item checklist for surgical performance (SP) score, measurement of procedure time and number of anastomoses missed. Eleven experts set the benchmark level of performance. Face validity and educational value of the simulator were assessed using a questionnaire.

RESULTS

Both groups showed an improvement in SP score at the post-training test compared with the pre-training test. The simulator-trained group significantly outperformed the control group, with a median SP score of 28 (54%) in the pre-test and 46 (88%) in the post-test vs 25 (48%) and 36 (69%), respectively (P = 0.008). Procedure time decreased by 11 min (from 44 to 33 min) in the study group vs 1 min (from 39 to 38 min) in the control group (P = 0.69). There was no significant difference in the number of missed anastomoses at the post-training test between the two groups (1 vs 0). Subsequent feedback provided by the participants indicated that training on the simulator was perceived as a useful educational activity.

CONCLUSIONS

Proficiency-based simulator training improves performance, indicated by SP score, for fetoscopic laser therapy. Despite the small sample size of this study, practice on a simulator is recommended before trainees carry out laser therapy for TTTS in pregnant women.