Insights into the pathophysiology of twin–twin transfusion syndrome

Comprehensive Metabolomic Profiling of Cord Blood and Placental Tissue in Surviving Monochorionic Twins Complicated by Twin-Twin Transfusion Syndrome With or Without Fetoscopic Laser Coagulation Surgery: A Retrospective Cohort Study

Objectives: To investigate metabolomic perturbations caused by twin-twin transfusion syndrome, metabolic changes associated with fetoscopic laser coagulation in both placental tissue and cord plasma, and to investigate differential metabolites pertinent to varying fetal outcomes, including hemodynamic status, birth weight, and cardiac function, of live-born babies.

Methods: Placental tissue and cord plasma samples from normal term or uncomplicated preterm-born monochorionic twins and those complicated by twin-twin transfusion syndrome treated with or without fetoscopic laser coagulation were analyzed by high-performance liquid chromatography metabolomic profiling. Sixteen comparisons of different co-twin groups were performed. Partial least squares–discriminant analysis, metabolic pathway analysis, biomarker analysis, and Spearman’s correlation analysis were conducted based on differential metabolites used to determine potential biomarkers in different comparisons and metabolites that are pertinent to neonatal birth weight and left ventricular ejection fraction.

Results: These metabolomic investigations showed that the cord plasma metabolome has a better performance in discriminating fetuses among different hemodynamic groups than placental tissue. The metabolic alteration of twin-twin transfusion syndrome in these two types of samples centers on fatty acid and lipid metabolism. The fetoscopic laser coagulation procedure improves the metabolomic change brought by this syndrome, making the metabolomes of the treated group less distinguishable from those of the control and preterm birth groups. Certain compounds, especially lipids and lipid-like molecules, are noted to be potential biomarkers of this morbid disease and pertinent to neonatal birth weight and ejection fraction.

Conclusions: Fetoscopic laser coagulation can ameliorate the metabolomic alteration caused by twin-twin transfusion syndrome in placental tissue and cord plasma, which are involved mainly in fatty acid and lipid-like molecule metabolism. Certain lipids and lipid-like molecules are helpful in differentiating co-twins of different hemodynamic statuses and are significantly correlated with neonatal birth weight or ejection fraction.

Double Trouble: Complications in Twin Pregnancies

With the increasing rate of twin pregnancies due to increase in maternal age and use of assisted reproduction, it is important to be aware of unique diseases which occur specifically to twin pregnancies, especially in monochorionic twin pregnancies. These entities include twin to twin transfusion syndrome, twin anemia polycythemia sequence, twin reversed arterial perfusion, cotwin demise, and conjoined twins. Early evaluation and documentation are imperative to guide management which ultimately leads to better patient outcomes.

Inter-twin differences in fetal echocardiographic findings are associated with decreased dual twin survival in twin-twin transfusion syndrome

OBJECTIVE

To determine if inter-twin differences in fetal echocardiographic findings are associated with fetal survival in monochorionic pregnancies complicated by twin-to-twin transfusion syndrome (TTTS).

METHODS

This study included women who underwent laser surgery for TTTS between 2012 and 2018 at a single institution. Echocardiographic cardiac parameters in the donor and recipient twins were compared using Z-scores and regression analyses (adjusted for confounding variables) to determine whether any measurable inter-twin differences were associated with neonatal survival at birth. Results are expressed as (Odds ratio [95% confidence interval], p-value).

RESULTS

Fetal echocardiography and delivery information was available in 124 TTTS cases. Dual live-birth occurred in 72% and at least one live-birth was seen in 89% of cases. Sixty-four percent (51/79) of recipient twins had evidence of cardiac dysfunction compared to 10% (8/79) of the donor twins (p < .01). In the logistic regression, inter-twin differences in left ventricle short axis dimension (0.62[0.44-0.87], p < .01), aortic valve diameter (0.67[0.45-0.99], p = .047), peak systolic velocity across the pulmonary artery (PA-PSV) (0.09[0.01-0.53], p < .01) and mitral valve diameter (0.56[0.38-0.84], p < .01) were associated with lower dual twin survival at birth.

CONCLUSION

Inter-twin differences in left cardiac geometry and function are associated with decreased survival at delivery in TTTS.

Reproductive Outcomes following Laser Surgery for Twin-Twin Transfusion Syndrome

BACKGROUND

There are limited studies describing future reproductive outcomes in women who have had selective fetoscopic laser photocoagulation (SFLP) for twin-twin transfusion syndrome (TTTS).

OBJECTIVE

Our study aims to compare reproductive outcomes following monochorionic multiple gestational pregnancies complicated by TTTS requiring SFLP to those not requiring SFLP.

METHODS

This is a retrospective cohort study that analyzed records of patients who were evaluated at the Cincinnati Fetal Center (2007-2014) for monochorionic multiple gestations. A questionnaire regarding reproductive, obstetric, gynecologic, and psychological outcomes following the index pregnancy was administered to consented participants by electronic distribution. The data was compared between pregnancies with prior SFLP versus no prior SFLP.

RESULTS

There was a higher response rate in the SFLP group (219/474, 46.2%) versus the referent group (62/187, 33.2%). The median interval between the index pregnancy and survey completion was 74 months and 46 months in the SFLP and referent groups, respectively. Approximately 38 and 37% of the women in the SFLP and referent groups attempted conception after the index pregnancy with a >90% pregnancy success rate in both groups. Use of assisted reproductive technology was highly prevalent in both the index and subsequent pregnancies, with no significant difference between the groups. Over 60% of the women in each group did not attempt future pregnancy. Of those, approximately 1 in 3 cited the outcome of the index pregnancy as the primary reason for not pursuing future conception. There were no significant differences in selected maternal-fetal complications and new-onset gynecologic problems. More than 1 in 4 women in both groups were diagnosed with a mental health disorder following the index pregnancy.

CONCLUSION

SFLP does not appear to be associated with adverse reproductive, obstetric, or gynecologic outcomes. The data may help facilitate evidence-based counseling for this patient population.

Maternal Complications and Hemodynamic Changes Following Intrauterine Interventions for Twin-to-Twin Transfusion Syndrome in Monochorionic Diamniotic Twin Pregnancies

Twin-to-twin transfusion syndrome (TTTS) is a challenging complication in monochorionic diamniotic (MCDA) twins. Intrauterine interventions, such as fetoscopic laser ablation and cord occlusion followed by amniodrainage, are established treatments. Little is known about maternal complications and hemodynamics following these interventions. We performed a retrospective analysis of maternal procedure-related complications and the impact of such procedures on maternal hemodynamics and blood characteristics. Within the study period, 100 women with severe TTTS treated by fetoscopic laser ablation (FLA) or cord occlusion (CO) were identified. Clinically relevant maternal complications were reported in four (4%) cases. There was a significant decrease in hemoglobin, hematocrit, and albumin between admission and postoperative measurements (all p < 0.001). Systolic and diastolic blood pressure, as well as maternal heart rate, decreased from time of skin suture to postoperative measurements (all p < 0.001). Within a 24 h interval, there was a positive correlation between hematocrit (Spearman's rho 0.325; p = 0.003), hemoglobin (Spearman's rho 0.379; p < 0.001), and albumin (Spearman's rho 0.360; p = 0.027), and the amount of amniodrainage during the intervention. Maternal procedure-related complications are relatively rare. Significant hemodynamic alterations and maternal hemodilution are common clinical findings following intrauterine interventions.

Discordance of umbilical coiling index between recipients and donors in twin-twin transfusion syndrome

INTRODUCTION

To compare the intertwin umbilical cord coiling in twin-twin transfusion syndrome (TTTS) before fetoscopic laser treatment and to correlate these with Doppler findings in both twins.

METHODS

We performed a prospective study using three-dimensional (3D) ultrasound with color Doppler imaging of the umbilical cord in TTTS. Coiling index was measured as a reciprocal value of one complete vascular coil. Ultrasound hypocoiling was thus defined as < 0.2 coils/cm and hypercoiling as > 0.6 coils/cm, respectively. Umbilical artery pulsatility index (PI) and peak systolic velocity, middle cerebral artery peak systolic velocity and ductus venosus PI of flow-velocity waveformes of both twins were measured.

RESULTS

We included 65 women in the study. The average gestational age was 21.1 ± 2.7 weeks. In 65 recipients and 56 donors coiling index could be quantified. The median (interquartile range) coiling index of recipient twins was significantly higher than of donors, 0.55 (0.41-0.68) vs. 0.26 (0.2-0.5); P < 0.0001. The proportions of abnormal intertwin coiling were significantly (P = 0.0015) different. Out of 65 recipient with coiling indices evaluation, 1 (1.5%) showed hypocoiled and 27 (41.5%) hypercoiled cords. In contrast, 27 donor twins (48.2%) showed hypocoiled and 5 (8.9%) hypercoiled umbilical cords. There were no significant correlations between the fetal Doppler values and coiling indices.

DISCUSSION

Evaluation of umbilical cord coiling index using 3D color Doppler in both twins complicated by TTTS is feasible in both, donors and recipients. Coiling indices differ significantly between recipient and donor twins and do not correlate with Doppler findings.

The value of ultrasound in predicting isolated inter-twin discordance and adverse perinatal outcomes

PURPOSE

To investigate the value of ultrasound approaching delivery to predict isolated inter-twin discordance and adverse perinatal outcomes.

METHODS

We retrospectively included twin pregnancies with sonography approaching delivery in ten maternal-foetal medicine centres in China from 2013 to 2014. Estimated foetal weight (EFW) and inter-twin EFW disparity (EFWD) were calculated based on biometry parameters. Percentage errors between EFW and actual birthweight or between EFWD and actual inter-twin disparity were calculated. ROC curves and multiple logistic regression were applied to evaluate the ability of EFWD to predict inter-twin disparity ≥ 25%, stillbirth, asphyxia and admission to a neonatal intensive unit (NICU). Chorionicity-stratified analysis was further performed.

RESULTS

Two hundred sixty-six monochorionic and 760 dichorionic twin pregnancies were analysed. The percentage errors in foetal weight estimations were 7-13%, whereas percentage errors in the estimation of inter-twin disparity were nearly 100%. Among eight formulas, Hadlock1 performed best, with a detectable rate of 65% and a false positive rate of 5% when predicting inter-twin disparity ≥ 25%. EFWD ≥ 22% was strongly associated with stillbirth (OR = 4.17, 95% CI 1.40-12.40) and NICU admission (OR = 3.48, 95% CI 2.03-5.97) after adjustment for gestational age, parity and abnormal umbilical systolic/diastolic ratio. Ultrasound had better predictive ability in monochorionic twins.

CONCLUSION

The predictive value of ultrasound for isolated inter-twin discordance and adverse perinatal outcomes was limited, which was possibly due to the magnifying of systematic errors in the disparity estimation compared with weight estimation. Despite this, abnormal biometry was an independent contributor for the poor prognosis of neonates.

Cardiac function and dysfunction in the fetus

Evaluation of fetal cardiac function is one of the most important components of fetal echocardiography. Fetal cardiac dysfunction is closely linked to risk of intrauterine fetal demise, in many, but not all cases is indicative of worse postnatal prognosis and may prompt the use of medications or interventions to optimize outcomes. There may be implications for termination versus continuation of pregnancy, an indication for early delivery, a change in location and even mode of delivery. In extreme cases, fetal cardiac dysfunction may prompt prenatal or early neonatal listing for cardiac transplantation. There are several important differences between the fetal and postnatal circulatory physiology which affect echocardiographic assessment of cardiac dysfunction. In this review, we examine the echocardiographic findings according to their underlying pathophysiology with reference to common causes.

Factors associated to early intrauterine fetal demise after laser for TTTS by preoperative fetal heart and Doppler ultrasound

OBJECTIVE

To determine the prognostic value of fetal Doppler and echocardiographic parameters for intrauterine fetal demise (IUFD) within 24 hours and within 1 week after laser coagulation in monochorionic pregnancies complicated by twin-twin transfusion syndrome.

METHOD

This retrospective study correlated the preoperative hemodynamic and echocardiography parameters to the outcome in fetuses with twin-twin transfusion syndrome undergoing laser therapy.

RESULTS

One hundred and twelve laser coagulations were performed between February 2006 and June 2015. The total (single and double) IUFD rate was 27.7%. Further, 59% of IUFD occurred within 24 hours and 74.4% occurred within 1 week after laser. The following were associated to IUFD within 24 hours: the middle cerebral arterial pulsatility index in the donor, abnormal umbilical artery (UA) end diastolic flow, increased middle cerebral artery peak systolic velocity, and right ventricular myocardial performance index (RV-MPI) z-score in the recipient. For IUFD within 1 week were the pulsatility index in the donor UA and the recipient abnormalities in UA, ductus venosus, middle cerebral artery-peak systolic velocity, and RV-MPI z-score.

CONCLUSION

Following laser was early IUFD that was associated with Doppler findings suggesting donor cerebroplacental redistribution, and recipient overload cardiomyopathy, such as abnormal ductus venosus and UA Dopplers as well as an increase of RV-MPI.

Fetoscopic laser photocoagulation for twin-twin transfusion syndrome

The aim of this study was to review fetoscopic laser photocoagulation (FLP), which ablates placental vascular anastomoses to treat twin–twin transfusion syndrome (TTTS). A review of studies reporting on the procedures, outcomes, complications and nonconventional applications of FLP for TTTS was conducted. FLP has been established as the primary treatment for monochorionic twin pregnancy associated with TTTS at 16–26 weeks. FLP is the only therapy that directly addresses the underlying pathophysiology. The recent technique modification of FLP, referred to as the ‘Solomon technique’, induces selective coagulation to connect the anastomoses ablation sites and has been introduced to reduce residual anastomoses. The perinatal survival following FLP improved significantly with advances in the technique after its introduction. The recent survival rates of both twins and at least one twin are 70% and more than 90%, respectively. However, there is still an 11–14% risk of long‐term neurodevelopment impairment. The premature rupture of membranes that leads to preterm labor is a common complication after FLP. FLP is a valuable treatment option for feto‐fetal transfusion syndrome in triplets and for TTTS after 26 weeks. FLP for selective intrauterine growth restriction may be potentially beneficial when accompanied by abnormal Doppler findings and oligohydramnios. FLP is the optimal treatment option for TTTS at 16–26 weeks of gestation. FLP appears to be applicable in triplets, TTTS after 26 weeks and cases of selective intrauterine growth restriction with abnormal Doppler findings and oligohydramnios. FLP is the most common and successful fetal intervention. Improvement in the neurodevelopmental outcomes after FLP is a future focus.

Estimated combined cardiac output and laser therapy for twin-twin transfusion syndrome

INTRODUCTION

Twin-twin transfusion syndrome (TTTS) is the major cause for fetal demise in monochorionic diamniotic pregnancies. Estimated combined cardiac output (CCO) has not been studied in this setting. The primary aims of this study were to compare CCO in twin donor and recipient fetuses and assess differences in CCO before and after laser coagulation therapy. A secondary aim was to evaluate the relationship of CCO with perinatal mortality, defined as intrauterine or neonatal mortality (≤30 days of age) in fetuses that underwent laser coagulation therapy.

METHODS

We performed a retrospective review of fetuses with TTTS who received echocardiograms prior to laser therapy. Prelaser echocardiograms were performed in 66 fetuses, of which 45 (21 donor and 24 recipient) survived to the postlaser echocardiogram.

RESULTS

Donor CCO increased from a mean of 487±137 mL/min/kg prelaser to 592±128 mL/min/kg postlaser (P=.025). There was no significant change in mean recipient CCO from prelaser 551±165 mL/min/kg to postlaser 575±112 mL/min/kg (P=.564). In recipient fetuses, higher prelaser CCO correlated with increasing Quintero stage (P=.010) and perinatal mortality (P=.003). Thirty-day postnatal outcome data were available for 38 fetuses, of whom 34 (89%) survived. Amongst survivors, 25 (74%) experienced an increase in CCO, while 9 (26%) experienced a decrease in CCO (P=.010). Donor fetuses had higher CCO after laser therapy.

CONCLUSIONS

Higher prelaser CCO in recipient fetuses may indicate more advanced disease. Fetuses who exhibit a decrease in CCO after therapy laser may be at higher risk for perinatal mortality.

Congenital Cytomegalovirus Infection in Monozygotic Twins with Twin-to-twin Transfusion Syndrome

BACKGROUND

Symptoms of congenital cytomegalovirus infection remains unclear.

CASE CHARACTERISTICS

Extremely low birth weight twins with twin-to-twin transfusion syndrome were infected with cytomegalovirus congenitally.

OBSERVATION

The donor showed neuronal impairment, whereas the recipient showed hepatic dysfunction.

MESSAGE

Intrauterine hemodynamics may be important in pathophysiology of congenital cytomegalovirus infection.

Maternal hypotension during fetoscopic surgery: incidence and its impact on fetal survival outcomes

In this retrospective cohort study, we aimed to determine the incidence of intraoperative maternal hypotension during fetoscopic surgery for twin-twin transfusion syndrome (TTTS) and to evaluate the impact of intraoperative hypotension on fetal survival. A total of 328 TTTS patients with recipient twin cardiomyopathy who underwent fetoscopic surgery under epidural anesthesia were included. The exposure of interest was maternal medical therapy with nifedipine for the treatment of fetal cardiomyopathy. We found that intraoperative hypotension occurred in 53.4% (175/328 patients). There was no statistically significant difference in incidence of hypotension between nifedipine exposure and nonexposure groups (54.8% versus 50.8%, P = 0.479). However, the nifedipine exposure group received a statistically significant higher dose of phenylephrine (7.04 ± 6.38 mcg/kg versus 4.70 ± 4.14 mcg/kg, P = 0.018) and higher doses of other vasopressor, as counted by number of treatments (6.06 ± 4.58 versus 4.96 ± 3.42, P = 0.022). There were no statistically significant differences in acute fetal survival rate (within 5 days) and fetal survival rate at birth between hypotensive and nonhypotensive patients. We concluded that preoperative exposure to nifedipine resulted in increased intraoperative maternal vasopressor requirement during fetoscopic surgery under epidural anesthesia. In patients who had intraoperative maternal hypotension, there was no correlation between the presence of maternal hypotension and postoperative fetal survival.

Prematurity and twinning

AIM OF THE STUDY

Newborns from multiple pregnancies are increasing in number and demonstrate a higher perinatal morbidity and mortality compared to singletons. Prematurity is the main reason for most neonatal diseases in twins, but other variables may play a role and their prenatal evaluation may improve the overall outcome.

MAIN FINDINGS

Prematurity is six times more frequent in twins and therefore birth weight is significantly lower compared to singletons. Thus, twins are more exposed to prematurity related diseases (respiratory, cardiovascular, infectious, etc.) and to long-term complications (especially neurological disabilities).

RESULTS

It is very difficult to estimate the increased risk of neonatal morbidity related to twinning independently to the increased risk of prematurity and therefore to interpret data on morbidity rates, in particular regarding the neurodevelopmental outcome.

CONCLUSION

Prevention of preterm birth is a primary goal in managing multiple pregnancies, together with prophylaxis with corticosteroids in order to improve foetal lung maturity. Accurate risk assessment strategies and adequate obstetrical-neonatological management of multiple pregnancies may reduce the increasing need for neonatal intensive care and for health resources in the long-term follow-up that has been observed over the last decades.

Fetoscopic laser therapy for twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) is a unique and complicated phenomenon occurring in 10-15% of monochorionic gestations. The chronic unbalanced distribution of blood volume across placental anastomoses between the donor and recipient fetuses leads to multisystem organ impairment including maladaptive changes in both fetuses. Fetoscopic selective laser photocoagulation (SLPC) is now established as the primary treatment modality for advanced stages of TTTS. SLPC is also associated with a risk reduction in fetal demise and long-term neurological impairment.

Altered fetal cerebral and cerebellar development in twin-twin transfusion syndrome

BACKGROUND AND PURPOSE

Neurodevelopmental disability is common in twins with TTTS in utero; however, the responsible neuropathology remains uncertain. We proposed to document the frequency of brain abnormalities on clinical fetal MR images and to determine if quantitative fetal brain biometric analysis in twin fetuses with TTTS was different from those in healthy control fetuses.

MATERIALS AND METHODS

We reviewed the fetal brain MR images of 33 twin pairs with TTTS clinically evaluated in our institution. Eighteen fetal MR images of "healthy" twins with TTTS were further studied with biometric analysis in comparison with GA-matched singleton fetuses to detect quantitative differences in brain growth and development.

RESULTS

A higher incidence of anomalies (11/33, 33.3%) was found than previously reported. The most frequent abnormality was ventriculomegaly (7/11, 63%) in both donor and recipient. In "healthy" twins with TTTS, biometric analysis revealed persistently small measurements (cBTD, CMT, TCD, and VAPD) in the donor cerebrum and cerebellum in comparison with their recipient cotwin and healthy control fetuses. These differences were preserved when normalized by cBTD.

CONCLUSIONS

Our findings show that significant brain abnormalities are common in TTTS. In addition, diffuse subtle abnormalities are also present in normal-appearing donor fetal brains that cannot be solely explained by overall growth restriction. Such subtle fetal brain anomalies may explain the high incidence of poor long-term neurodevelopmental outcomes of survivors, and they need to be further investigated with more sophisticated quantitative fetal imaging methodologies.

[Fetoscopic laser coagulation in 100 consecutive monochorionic pregnancies with severe twin-to-twin transfusion syndrome]

OBJECTIVES

To report pre- and post-surgical datas of large series of severe twin-to-twin transfusion syndrome (TTTS) managed with laser ablation surgery in our centre, to evaluate the incidence of complications, perinatal outcome and to compare with other cohorts.

PATIENTS AND METHODS

Observational study of 100 cases of TTTS consecutively treated with fetoscopic laser coagulation between January 2004 and April 2010 in CMCO-SIHCUS of Schiltigheim.

RESULTS

There are nine stage I, 49 stage II, 38 stage III and four stage 4. Median gestation at time of laser is 20.6 weeks (14-29) whereas median gestation at delivery is 32.6 weeks (16.3-39). Overall perinatal survival rate is 68.5% (137 children over 200). Eighty-five percent have one or more surviving twins. The survival rate is the same for donors and for recipients. Preterm premature rupture of the membranes are observed in 17% of cases and the median gestational age for this complication is 30 weeks (20-34). Cerebral abnormalities are present in 7% of newborns.

CONCLUSION

Our results for the management of severe TTTS are comparable to the other reported series. There are still many questions remaining concerning the optimal management of TTTS.

Doppler imaging using spectrally-encoded endoscopy

The capability to image tissue motion such as blood flow through an endoscope could have many applications in medicine. Spectrally encoded endoscopy (SEE) is a recently introduced technique that utilizes a single optical fiber and miniature diffractive optics to obtain endoscopic images through small diameter probes. Using spectral-domain interferometry, SEE is furthermore capable of three-dimensional volume imaging at video rates. Here we show that by measuring relative spectral phases, this technology can additionally measure Doppler shifts. Doppler SEE is demonstrated in flowing Intralipid phantoms and vibrating middle ear ossicles.

Initial fetal cardiovascular profile score predicts recipient twin outcome in twin-twin transfusion syndrome

BACKGROUND

The aim of this study was to assess the relationship between cardiomyopathy and recipient twin (RT) outcome in twin-twin transfusion syndrome (TTTS).

METHODS

Fetal echocardiography and outcomes data in 62 consecutive pregnancies with TTTS were reviewed. The primary outcome was neonatal RT survival. The severity of RT cardiomyopathy at presentation was assessed by the cardiovascular profile score (CVPS). RT outcomes and odds of survival were compared between groups stratified by CVPS.

RESULTS

Overall neonatal survival for all fetuses was 61% (76 of 124). RT survival was 58% (36 of 62). Grouped by CVPS, RT survival was greater (50%) for those with CVPS > or = 9 and even higher (74%) for CVPS of 10. Among the components of the CVPS, atrioventricular valve regurgitation was associated with negative RT outcome. Other factors at presentation were not predictive of RT outcome.

CONCLUSIONS

A normal CVPS in the RT in TTTS is predictive of improved survival compared with an abnormal CVPS, even in RTs with minor deductions. Standard clinical staging did not predict outcome. Cardiac assessment by CVPS may improve clinical decision making and the timing of fetal interventions.

Twin-to-twin transfusion syndrome: an antiangiogenic state?

OBJECTIVE

An imbalanced chronic blood flow between the donor and recipient twin through placental vascular anastomoses is the accepted pathophysiology of twin-to-twin transfusion syndrome (TTTS). Vascular endothelial growth factor receptor-1 (VEGFR-1) mRNA is overexpressed only in the syncytiotrophoblast of the donor twin in some cases of TTTS. This study was conducted to determine maternal plasma concentrations of placental growth factor (PlGF), soluble VEGFR-1, and soluble endoglin (s-Eng) in monochorionic-diamniotic pregnancies with and without TTTS.

STUDY DESIGN

This case-control study included monochorionic-diamniotic pregnancies between 16-26 weeks with and without TTTS. Maternal plasma concentrations of PlGF, sVEGFR-1, and s-Eng were determined with ELISA. A P value < .05 was considered statistically significant.

RESULTS

Patients with TTTS had higher median plasma concentrations of s-Eng (14.8 ng/mL vs 7.8 ng/mL; P < .001) and sVEGFR-1 (6383.1 pg/mL vs 3220.1 pg/mL; P < .001]; and lower median plasma concentrations of PlGF (115.5 pg/mL vs 359.3 pg/mL; P = .002) than those without TTTS.

CONCLUSION

We propose that an antiangiogenic state may be present in some cases of TTTS.

The influence of twinning on cardiac development

The risk for a cardiac anomaly in a twin pregnancy is increased, particularly in monochorionic twins. This is relevant in terms of fetal diagnosis as well as for the management of the pregnancy; there are also implications for the neonatal period and possibly beyond. The risk for a cardiac abnormality depends on the type of monochorionic twin as determined by the timing of embryonic division. Prenatal identification of twin type and the relative risks for a cardiac anomaly are discussed along with theories for the aetiology of the different cardiac lesions.

Endoscopic laser surgery in severe second-trimester twin-twin transfusion syndrome: a three-year experience from a Latin American center

OBJECTIVE

In order to assess the outcome of pregnancies complicated by severe second trimester twin-twin transfusion syndrome (TTTS) undergoing treatment with endoscopic laser surgery, we reviewed our experience following the implementation of an institutional fetal surgery program.

METHODS

Patients presenting with monochorionic-diamniotic twin pregnancies complicated by severe TTTS before 26 weeks of gestation were offered endoscopic laser surgery to coagulate placental vascular anastomoses. Using regional anesthesia and guided by real-time sonography, anastomoses were identified and selectively coagulated. At the end of the procedure, amniodrainage was performed to restore normal amniotic fluid volume. Follow-up and delivery were carried out at the referring institutions. Six-month follow-up was performed in all cases.

RESULTS

During a 3-year period from September 2003 to December 2006, 33 consecutive cases of severe TTTS were operated on at a median gestational age of 21 weeks (range 17-25). Nine (27.3%) cases were classified as stage II, 21 (63.6%) as stage III, and three (9.1%) as stage IV. The placenta was anterior or predominantly anterior in 15 (45.5%) of the cases. Overall, both twins were born alive in 16 (48.5%) cases, only one twin was born alive in 11 (33.3%), and neither was born alive in the remaining six (18.2%). Therefore, 81.8% (27 of 33) of the pregnancies resulted in at least one liveborn infant. Among them, the mean gestational age at delivery was 32 weeks (range 23-38) and the mean birthweight of the liveborn infants was 1591 g (range 350-3800). Thirty-four infants survived the perinatal period, yielding an overall perinatal survival rate of 51.5%, with 75.8% (25 of 33) of the pregnancies resulting in at least one perinatal survivor. All neonatal deaths were associated with extreme prematurity.

CONCLUSIONS

This preliminary experience suggests that selective laser coagulation appears to be a good treatment option in cases of monochorionic twin pregnancies complicated by severe TTTS. However, technical skills and adequate equipment are required for implementing a fetal surgery program. Auditing outcomes during the learning curve would help in identifying potential problems.

Stage I twin-twin transfusion syndrome: rates of progression and regression in relation to outcome

OBJECTIVES

Twin-twin transfusion syndrome (TTTS) results in high rates of perinatal mortality and neurological morbidity. Fetoscopic laser ablation of placental anastomoses is now established as the treatment of choice for advanced disease. However, there remains controversy about its use in early-stage TTTS, in which laser-related fetal losses need to be balanced against relatively favorable outcomes with more conservative approaches. We investigated rates of progression and regression in Stage I TTTS and determined factors influencing the course of the disease.

METHODS

We undertook a retrospective observational study of all TTTS cases referred to our tertiary referral fetal medicine service from 2000 to 2006. In patients presenting with Stage I TTTS, the following variables were evaluated for their ability to predict the course and progression of the disease: gestational age (GA) at presentation, amniotic fluid index, recipient and donor deepest vertical pool, presence of artery-artery anastomoses, small-sized bladder compared to normal donor bladder and fetal size discordance. Study end-points were disease regression or progression, and neonatal survival at 28 days.

RESULTS

Among 132 consecutive cases of TTTS, 46 women presented with Stage I disease. In the majority (69.6%), disease remained stable (28.3%) or regressed (41.3%). Of cases that progressed, 79% did so within 2 weeks and 93% progressed to at least Stage III. No factor was significantly linked with progression or regression, although there was a trend towards the absence of an artery-artery anastomosis (P = 0.10) and the presence of a small rather than normal donor bladder (P = 0.10) influencing progression, and later GA at presentation (P = 0.07) influencing regression. At least one infant survived in 83% of cases and there was double survival in 59%. Perinatal outcome was significantly better in cases that regressed (the rates of at least one survivor and double survival being 89% and 89%, respectively) or remained Stage I (77% and 61%, respectively), compared with those cases that progressed (79% and 14%, respectively). Treatment with amnioreduction at first presentation did not influence progression or regression.

CONCLUSIONS

This study demonstrates that a high percentage of Stage I TTTS cases regress or remain early stage. Identification of factors predicting progression would facilitate the selection of patients for definitive therapy, while avoiding treatment-related morbidities in mild or transient disease.

The twin-twin transfusion syndrome: spectrum of cardiovascular abnormality and development of a cardiovascular score to assess severity of disease

OBJECTIVE

Current means of grading twin-twin transfusion syndrome does not characterize cardiovascular aspects adequately. We sought to develop a score that describes the magnitude of cardiovascular severity in twin-twin transfusion syndrome.

STUDY DESIGN

Fetal echocardiograms of 150 monochorionic/diamniotic twins were reviewed. Blinded to Quintero stage, we applied a cardiovascular score to each twin set and compared it to the Quintero grade. The score is a composite of variables that include ventricular hypertrophy, dilation, function, valve regurgitation, great artery size, and diastolic properties in the recipient and umbilical artery flow in the donor. Doppler indices of vascular and ventricular function were measured.

RESULTS

Mean age was 21 +/- 3 weeks. Discrepancy was noted in degree of severity between Quintero and cardiovascular stages. The score correlated well with myocardial performance index of the recipient right ventricle (r2 = .65).

CONCLUSION

We describe the spectrum of cardiovascular abnormalities that are seen in twin-twin transfusion syndrome and propose a scoring system for assessment of severity.

A retrospective analysis of placentas from twin pregnancies derived from assisted reproductive technology

There are conflicting studies associating twin pregnancies derived from assisted reproductive technology (ART) with preterm birth, low birthweight, and other negative outcomes. This work investigates whether ART is linked with any placental pathology, given that placentation significantly influences fetal development. A 5-year, retrospective cohort study was conducted on placentas from twin pregnancies. The placental information from 417 patients was divided into two groups: placentas derived from ART and placentas derived from spontaneous pregnancies (non-ART). Available clinical information and pathologic findings from both groups then were compared. There was no statistical difference in the prevalence of placental pathology between the non-ART and ART cohorts (i.e., cord insertion, single umbilical artery, cord knot, retroplacental hemorrhage, infarction, vasculopathy, vascular anastomoses, chorangiosis, villitis, deciduitis, chorioamnionitis, meconium staining). However, 8% of ART multiple pregnancies were monochorionic. While monochorionicity is a known risk factor for adverse obstetric and neonatal outcomes, the rate of monochorionic placentation did not increase as a result of ART. Nevertheless, it is interesting to note that this small percentage of monochorionic placentation occurred in the ART cohort despite the implantation of individual embryos. Overall, the data suggests that ART does not have a role in the pathologic placentation of twin pregnancies.

Impact of altered loading conditions on ventricular performance in fetuses with congenital cystic adenomatoid malformation and twin-twin transfusion syndrome

OBJECTIVES

In the fetus with a structurally normal heart, two conditions--giant chest mass, such as congenital cystic adenomatoid malformation (CCAM), and twin-twin transfusion syndrome (TTTS)--alter ventricular loading conditions and may result in cardiovascular compromise. The aim of this study was to elucidate the mechanism of cardiovascular dysfunction by comparing geometry-independent, Doppler flow-derived measures of ventricular performance in fetuses with altered loading conditions vs. those in normal fetuses.

METHODS

Doppler flow-derived measures of myocardial performance index (MPI) as described by Tei, ventricular ejection force as described by Isaaz, and combined cardiac output (CCO) were obtained by echocardiography in fetuses with a normal cardiovascular system (n = 76) or CCAM (n = 36) and fetal partners with TTTS (n = 22).

RESULTS

In the CCAM group, systolic performance as evidenced by the ejection forces was preserved, right ventricular (RV) MPI was increased and CCO diminished, suggesting diastolic dysfunction and poor filling secondary to cardiac compression and a tamponade effect. In TTTS, recipient twins exhibited greater left ventricular (LV) ejection forces and higher CCO than donor twins, and had abnormal RV and LV MPI, reflecting increased preload, preserved left systolic performance, but diastolic dysfunction. Donor twins had diminished ejection forces and CCO in comparison with normal controls and recipient partners, reflecting hypovolemia.

CONCLUSIONS

In both CCAM and recipient twins of the TTTS, diastolic dysfunction plays a significant role in the pathophysiology of each disorder and precedes changes in systolic performance. Measures of ventricular performance can help elucidate poorly understood mechanisms of cardiovascular compromise in the developing fetus.

Twin-Twin Transfusion Syndrome Modeling

The twin-twin transfusion syndrome (TTTS) is a severe complication occurring in monochorionic twins, and untreated, causes high rates of mortality and morbidity. In TTTS, five consecutive stages of increasing severity can be distinguished: first, the oligopolyhydramnios sequence; second, anuria in the donor twin; third, abnormal flow waves in either twin; fourth, a hydropic recipient, and finally the fifth stage, fetal demise of either twin. Recently, we developed a mathematical model of the Stages I-IV. In this report, we investigated the influence of amnioreduction and laser therapy at two different gestational ages on the resolution of TTTS Stage III. Simulations were performed for two gestational ages, at 22 and 28 weeks; that is, at the onset of a stuck donor twin and when TTTS has progressed to an anuric donor with abnormal umbilical flow waves and a hydropic recipient, respectively. Results indicate abnormal umbilical flow waves in the donor to resolve rapidly after both amnioreduction and laser therapy. TTTS and abnormal umbilical flows in the donor, however, return after amnioreduction. Laser therapy, leading to cessation of fetofetal transfusion, produces complete resolution of TTTS sequelae, however, with increased vascular stiffness in the donor. Amnioreduction and laser therapy both produce rapid resolution of abnormal umbilical flows in a mathematical model of TTTS. Laser ablation of all anastomoses, however, completely ceases the fetofetal transfusion, so that no TTTS redevelops. In the donor, vascular stiffness remains increased after laser, suggesting increased pulse wave velocities can be measured clinically.

Velamentous cord insertion and unequal placental territories in monochorionic twins with and without twin-to-twin-transfusion syndrome

OBJECTIVE

The objective of this study was to determine the incidence of velamentous cord insertion and placental territory discordancy in monochorionic twins with and without twin-to-twin transfusion syndrome (TTTS).

STUDY DESIGN

All consecutive placentas of monochorionic twins delivered at our center between June 2002 and April 2006 were studied with vascular injection of the umbilical vessels with colored dyes. Velamentous cord insertions were recorded and individual placental territories were calculated by computer analysis.

RESULTS

A total of 76 monochorionic placentas with TTTS and 63 monochorionic placentas without TTTS were studied. The incidence of velamentous cord insertion (per fetus) in the TTTS group and the non-TTTS group was 13% (20 of 152) and 14% (18 of 126), respectively (P = .79). Placental territory discordancy in the TTTS group and the non-TTTS group was 20% and 20% (P = 0.83). In the TTTS group, donor twins had a velamentous cord insertion more often than recipient twins (24% and 3%, respectively, P < .001) and a smaller placental territory (44% and 56%, respectively, P < .001).

CONCLUSION

Our findings suggest that velamentous cord insertion and unequal placental territory are not critical factors for the development of TTTS.

Twin-twin transfusion syndrome: cerebral ischemia is not the only fetal MR imaging finding

BACKGROUND

Twin-twin transfusion syndrome (TTTS) is a complication of monochorionic/diamniotic twin pregnancies. An imbalance of blood flow occurs through placental anastomoses, causing potentially significant morbidity and mortality in both twins. Although the sonographic findings of TTTS are well documented, we believe that MR imaging is a valuable adjunct.

OBJECTIVE

We describe the fetal MR imaging findings associated with TTTS.

MATERIALS AND METHODS

From 2003 to 2005, 37 consecutive MR imaging studies were performed on multiple-gestation pregnancies. Of the 37, 25 were consistent with TTTS, correlated and confirmed by sonographic criteria. MR fetal abnormalities were documented.

RESULTS

Cerebral ischemia, which could not be demonstrated by sonography, was delineated well by MR imaging. New findings noted on fetal MR imaging were enlargement of cerebral venous sinuses in both twins, dilatation of the renal collecting system in the recipient, lung lesions in the recipient and cerebral malformations in the donor.

CONCLUSION

MR imaging is an important adjunct in TTTS imaging. Its benefit over sonography is its clear definition of cerebral pathology, which is important for intervention and counseling. The new findings, particularly in the urinary tract and cerebral venous sinuses, also help support the diagnosis of TTTS and might reveal additional consequences of the altered hemodynamics that occur in TTTS.

Impact of selective laser ablation of placental anastomoses on the cardiovascular pathology of the recipient twin in severe twin-twin transfusion syndrome

OBJECTIVES

We investigated the impact of selective laser ablation on the cardiovascular pathology of the recipient twin in twin-twin transfusion syndrome.

STUDY DESIGN

Fetal echocardiograms and medical records were reviewed from 22 pregnancies with severe twin-twin transfusion syndrome where echocardiography was performed before and after laser.

RESULTS

Before laser, cardiomegaly associated with right and/or left ventricular hypertrophy without ventricular dilatation, was observed in most cases. Right ventricular and left ventricular systolic dysfunction (shortening fraction <28%) was present in 59% and 27%, respectively, and diastolic dysfunction (based on inflow and venous Dopplers) in 73%. Shortly after laser, biventricular systolic function improved significantly and diastolic function tended to improve (50%, P = .06). Functional pulmonary atresia, secondary to right ventricular systolic dysfunction, resolved in 2 of 2 cases at post-laser echocardiography. On serial assessment, diastolic function was normal in 7 of 10, hydrops regressed in 4 of 5, and neither progressive myocardial hypertrophy nor anatomical right ventricular outflow obstruction were found.

CONCLUSIONS

Selective laser ablation in severe twin-twin transfusion syndrome acutely improves biventricular systolic function and tends to improve diastolic function in the recipient twin.

Venous Doppler in the assessment of fetal cardiovascular status

PURPOSE OF REVIEW

The purpose of this review is to highlight recent developments in the Doppler assessment of the fetal venous circulation with special reference to clinical applications in the human fetus.

RECENT FINDINGS

Doppler evaluation of the fetal venous circulation has increased our understanding of fetal cardiovascular function. Examples include the regulatory role of the ductus venosus in fetal nutrient partitioning and the significance of venous and arterial circulatory watershed areas. Alterations in cardiac afterload, contractility compliance, intravascular volume status and heart rate modulate venous and arterial flow velocity waveforms. Concurrent examination of these cardiovascular factors is of great importance in fetal growth restriction, complicated monochorionic multiple gestation, fetal hydrops and arrhythmia. In these conditions, comprehensive Doppler assessment provides critical diagnostic and prognostic information and has a key role in directing interventions.

SUMMARY

Venous Doppler has added a critical dimension to the understanding of fetal cardiovascular pathophysiology. In both health and disease, venous Doppler must now occupy a fundamental position in the comprehensive assessment of the fetal circulation.