The Placenta Contributes to Activation of the Renin Angiotensin System in Twin–Twin Transfusion Syndrome

Maternal hemodynamic evaluation in monochorionic twin pregnancy complicated by twin-to-twin transfusion syndrome treated with fetoscopic laser surgery

BACKGROUND

Maternal cardiovascular adaptations are amplified in twin pregnancies to support the metabolic request of the feto-placental unit. Few studies have evaluated the maternal hemodynamics changes after routine use of laser surgery in the treatment of twin-twin transfusion syndrome.

OBJECTIVE

The aim of our study was to evaluate hemodynamic changes in monochorionic twin pregnancies complicated by twin-twin transfusion syndrome before and after treatment with fetoscopic laser surgery.

STUDY DESIGN

A prospective observational study from 2020 to 2022, included monochorionic twin pregnancies complicated with twin-twin transfusion syndrome undergoing laser surgery between 16 and 26 weeks of gestation. To assess placental function and perfusion, uterine artery pulsatility index, hemoglobin, hematocrit, and soluble fms-like tyrosine kinase-1/placental growth factor ratio sampling prelaser and 24 hours postlaser were measured. Echocardiography by a single cardiologist evaluated maternal hemodynamics at presurgery, 24 hours, and 1 week postlaser. Those data were crosswise compared with cardiovascular indices of uncomplicated monochorionic pregnancies recruited at the same gestational age using nonparametric tests. Moreover, we fitted random-intercept linear regression models to investigate maternal hemodynamic changes according to the amount of amniotic fluid drained during laser surgery.

RESULTS

Forty-two twin-twin transfusion syndrome pregnancies with a median gestational age of 19.1 (17.4-20.9) weeks and 15 uncomplicated monochorionic pregnancies at the same gestational age were enrolled. Overall survival rate after laser was 72% with delivery at a median gestational age of 31.5 (27-34) weeks. Significant changes in blood chemistry and placental function were observed in the twin-twin transfusion syndrome group, along with alterations in arterial pressure, heart rate, cardiac output, and ventricular strain, eventually aligning with the uncomplicated group's values by 1 week postlaser. The amount of amniodrainage, with a 1000 ml cut-off, did not significantly impact hemodynamic parameters. Lastly, we detected a percentage of laser surgery complications in agreement with international literature and we did not record any maternal procedure-related problems.

CONCLUSION

Our analysis highlighted that maternal cardiovascular status in monochorionic twin pregnancy complicated by twin-twin transfusion syndrome was more dynamic and; 1 week after fetoscopic laser ablation of placental anastomosis completed by amniodrainage, maternal hemodynamic parameters restored to values similar to uncomplicated monochorionic twin pregnancies.

Molecular Mechanisms Underlying Twin-to-Twin Transfusion Syndrome

Twin-to-twin transfusion syndrome is a unique disease and a serious complication occurring in 10–15% of monochorionic multiple pregnancies with various placental complications, including hypoxia, anemia, increased oxidative stress, and ischemia-reperfusion injury. Fetoscopic laser photocoagulation, a minimally invasive surgical procedure, seals the placental vascular anastomoses between twins and dramatically improves the survival rates in twin-to-twin transfusion syndrome. However, fetal demise still occurs, suggesting the presence of causes other than placental vascular anastomoses. Placental insufficiency is considered as the main cause of fetal demise in such cases; however, little is known about its underlying molecular mechanisms. Indeed, the further association of the pathogenic mechanisms involved in twin-to-twin transfusion syndrome placenta with several molecules and pathways, such as vascular endothelial growth factor and the renin–angiotensin system, makes it difficult to understand the underlying pathological conditions. Currently, there are no effective strategies focusing on these mechanisms in clinical practice. Certain types of cell death due to oxidative stress might be occurring in the placenta, and elucidation of the molecular mechanism underlying this cell death can help manage and prevent it. This review reports on the molecular mechanisms underlying the development of twin-to-twin transfusion syndrome for effective management and prevention of fetal demise after fetoscopic laser photocoagulation.

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.

Twin gestation and the burden of adult cardio-renal disease

The rate of twin births has increased by nearly 80% in recent decades largely due to advanced reproductive technologies. Twins are often born preterm and/or growth restricted which are independently associated with impaired renal and vascular development. Many preterm and twin infants are surviving into adulthood, albeit with an increased burden of chronic health conditions. Twinning as a research tool offers the unique opportunity to investigate the impact of genetics versus the environment on clinical outcomes. This educational review will focus on delineating our current understanding of the renal and cardiovascular development and long-term outcomes among twin born individuals. Specifically, existing literature regarding how twins differ in kidney size and function as well as vascular stiffness and hypertension profiles from singletons will be discussed. The unique situation of twin-twin transfusion syndrome which is associated with distinct short- and long-term cardio-renal disease will be highlighted. Ultimately, the ability to stratify risk of future cardio-renal disease at birth for infants born preterm and/or growth restricted, including twins, is important to guide clinical follow up. In addition, this early risk stratification could direct research efforts to better understand the mechanisms driving impaired organogenesis and allow for discovery of therapeutic interventions aimed at modifying disease progression and improving longevity in the most vulnerable infant subgroups.

Placental Anatomy and Function in Twin Gestations

With an increasing incidence of twin gestations, understanding the inherent risks associated with these pregnancies is essential in modern obstetrics. The unique differences in placentation in twins contribute to the increased risks. Monochorionic twins are susceptible to complications because of their unique placental architecture, including twin-to-twin transfusion syndrome, the twin anemia-polycythemia sequence, selective intrauterine growth restriction, and the twin reversed arterial perfusion sequence. Knowing the clinical correlations of placental anatomy in these gestations helps perinatal pathologists perform a more informed placental evaluation, allowing for better care for the mother and her children.

Renal artery Doppler studies in the assessment of monochorionic, diamniotic twin pregnancies with and without twin-twin transfusion syndrome

BACKGROUND

In monochorionic, diamniotic twin pregnancies complicated by twin-twin transfusion syndrome, imbalanced fetofetal blood shunting and discordant activation of the renin-angiotensin system result in a hypovolemic, oliguric donor twin and a hypervolemic, polyuric recipient twin. Renal artery Doppler assessments have been reported to predict oligohydramnios in singleton pregnancies; however, their value in assessing monochorionic, diamniotic twin gestations, including pregnancies complicated by twin-twin transfusion syndrome, remains unstudied.

OBJECTIVE

This investigation evaluated whether renal artery Doppler parameters are different between sets of monochorionic, diamniotic twins with and without twin-twin transfusion syndrome.

STUDY DESIGN

We conducted a prospective study of women with monochorionic, diamniotic twin pregnancies complicated by twin-twin transfusion syndrome and women with gestational-age matched monochorionic, diamniotic twin control pregnancies without twin-twin transfusion syndrome. For each twin, renal artery Doppler assessment was performed from a coronal view of the fetus, and pulsatility index, resistive index, and peak systolic velocity were measured. In twin pairs complicated by twin-twin transfusion syndrome, renal artery Doppler pulsatility index, resistive index, and peak systolic velocity intertwin ratios were calculated by comparing paired recipient-to-donor values. Similar ratios were calculated for control twin pairs. We compared each measurement between donors and controls and between recipients and controls. Intertwin ratios were compared between twin-twin transfusion syndrome cases and monochorionic, diamniotic controls. Our primary outcome was a comparison of renal artery Doppler pulsatility index measurement between donor fetuses in twin-twin transfusion syndrome cases and matched control twins. Secondary outcomes included comparisons of other renal artery Doppler parameters between twin-twin transfusion syndrome donor twins and controls and between twin-twin transfusion syndrome recipients and controls and comparisons of the renal artery Doppler parameter ratios between twin-twin transfusion syndrome and non-twin-twin transfusion syndrome twin pair groups. Finally, we performed a subgroup analysis involving pregnancies with twin-twin transfusion syndrome that underwent fetoscopic laser therapy and resulted in twin survivors to evaluate if laser therapy influenced renal artery Doppler findings.

RESULTS

We recruited 12 donors and 12 controls. Renal artery Doppler pulsatility index and resistive index did not differ between donors and controls. However, donor renal artery Doppler peak systolic velocity (median, 14.24 [11.51-15.36]) was significantly lower than that of controls (median, 24.79 [22.46-27.03]; P<.0004). When recipient twins were compared with controls, there was no difference in renal artery Doppler pulsatility index, renal artery Doppler resistive index, or renal artery Doppler peak systolic velocity. Renal artery Doppler peak systolic velocity ratios were significantly higher among cases with twin-twin transfusion syndrome (median, 1.70 [1.53-2.02]) than controls (median, 1.06 [1.03-1.15]; P=.002). Applying a renal artery Doppler peak systolic velocity ratio cutoff of >1.35 for the diagnosis of twin-twin transfusion syndrome correctly classified 11 of 12 cases with twin-twin transfusion syndrome and all 12 controls without twin-twin transfusion syndrome (92% sensitivity and 100% specificity). Among donors with twin-twin transfusion syndrome with double survivors after undergoing laser therapy (n=4), prelaser renal artery Doppler peak systolic velocity ratios (mean, 1.46; standard deviation, 0.37) were significantly higher than postlaser renal artery Doppler peak systolic velocity ratios (mean, 0.87; standard deviation=0.37; P=.02). Postlaser intertwin renal artery Doppler peak systolic velocity ratios did not differ from control twin pairs (P=.125).

CONCLUSION

Renal artery Doppler peak systolic velocity ratios differ between monochorionic, diamniotic twins with twin-twin transfusion syndrome and those without twin-twin transfusion syndrome. This effect seems to be driven by altered donor twin renal artery Doppler peak systolic velocity. Laser therapy may normalize renal artery Doppler peak systolic velocity ratios and donor twin renal artery Doppler values to those observed in monochorionic, diamniotic twins without twin-twin transfusion syndrome. Further study is warranted to explore whether renal artery Doppler peak systolic velocity has utility as a tool for twin-twin transfusion syndrome prediction, diagnosis, or staging, and fetal response to laser therapy.

Renal functional markers in extremely premature infants with and without twin-twin transfusion syndrome

OBJECTIVE

Describe renal function of preterm infants <29 weeks of gestational age (GA) with twin-twin transfusion syndrome (TTTS) who received laser therapy.

DESIGN

Retrospective analysis of premature TTTS compared with dichorionic-diamniotic (di-di) twins from 2006 to 2015. Primary outcome was biomarkers of renal injury.

RESULTS

Thirty-three TTTS-laser and 101 di-di newborns with similar GA at birth (26.4 ± 1.4 vs 26.9 ± 1.6 weeks, p = 0.07) were included. Creatinine and urea levels were higher in TTTS-laser group at day of life (DOL) 2-7 (123.5 ± 12.4 vs 75.8 ± 2 μmol/L, p = 0.0001 and 11.9 ± 1.1 mmol/L vs 8.7 ± 0.3 mmol/L, p = 0.0001) and DOL 8-14, (98.1 ± 14.2 vs 64.8 ± 2.3 μmol/L, p = 0.0001 and 9.1 ± 1.2 vs 5.4 ± 0.3 mmol/L, p = 0.0001). There was a significant effect of TTTS status on creatinine level at DOL 8-14.

CONCLUSION

In extremely preterm with TTTS treated by laser, biomarkers of renal function were higher compared with di-di twins in the first 2 weeks of life.

Fetal cardiovascular alterations in twin-to-twin transfusion syndrome

Twin-to-twin transfusion syndrome (TTTS) is the consequence of vascular anastomoses of the shared placenta of monochorionic twin pregnancies. Both circulating inter-twin blood flow and vasoactive mediators imbalance cause hypovolemia in the donor and hypervolemia in the recipient fetus. If left untreated, TTTS has a high perinatal mortality rate and adverse long-term outcomes mainly cardiovascular and neurological. The recipient has cardiovascular changes including atrioventricular valve regurgitation, diastolic dysfunction and pulmonary stenosis/atresia. The maladaptive response to vascular changes determines a constant decreased blood flow in the donor that permanently modifies the arterial structure leading to postnatal alterations in the vascular system. Fetoscopic LASER surgery of placental vascular anastomoses may disrupt the underlying pathophysiology and improves cardiovascular function with normalization of systolic and diastolic function within weeks after treatment. The impact of cardiovascular changes is relevant for the safety of the management of a TTTS case. The improvement of the perinatal survival after intrauterine surgery leads to viable infants with the longer-term sequelae. Therefore accurate quantification of cardiovascular involvement is essential for clinicians for pregnancy management but also for patient counseling about the potential treatment options the outcome.

Twin-twin transfusion syndrome in the era of fetoscopic laser surgery: antenatal management, neonatal outcome and beyond

Introduction: Twin-twin transfusion syndrome (TTTS) is a devastating complication of monochorionic twin pregnancy and remains a major challenge for worldwide fetal medicine specialists. In TTTS, intertwin transfusion through vascular anastomoses in the shared placenta leads to severe hemodynamic imbalance. This review summarizes the current knowledge of TTTS.Areas covered: The most recent insights concerning the management of TTTS, as well as fetal and neonatal complications are described. Relevant articles were selected based on a Pubmed search using the keywords below. Understanding of the underlying pathophysiology has improved greatly as a result of placental injection studies. Advancements in antenatal management have led to increased perinatal survival and a decreased incidence of neonatal complications, including brain injury and neurodevelopmental impairment.Expert opinion: Further opportunities for improvement comprise technological innovations in laser procedures and the prevention of preterm rupture of membranes with subsequent prematurity. A noninvasive treatment such as high-intensity focused ultrasound (HIFU) seems to hold promise for the future treatment of TTTS. Fetal MRI studies are important to improve our understanding of fetal brain injury and should relate their findings to long-term neurodevelopment. International collaboration and centralization of care are of paramount importance to ensure the best care for our patients.

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.

Chronic kidney disease following twin-to-twin transfusion syndrome-long-term outcomes

BACKGROUND

Amongst other sequelae, acute kidney injury (AKI) is a well-recognised post-natal complication of twin-to-twin transfusion syndrome (TTTS). Despite this, there has been a lack of data reporting long-term renal outcomes. Our aim was to report the long-term renal outcomes of infants born with TTTS.

METHODS

We performed a retrospective case note review of all infants referred to our centre between 1998 and 2018 with a primary diagnosis of TTTS. Subjects with confirmed TTTS were divided into a chronic kidney disease (CKD) group and a non-CKD group for comparison.

RESULTS

Twenty-six infants with TTTS were included for analysis. Eight (31%) subjects developed CKD. Within the CKD group, 50% went on to require long-term renal replacement therapy (RRT) of whom all underwent renal transplantation. For subjects who had neonatal AKI, cumulative survival rate before RRT at 5 and 10 years was 79% and 70%, respectively. Subjects with CKD had a significantly higher incidence of AKI in the neonatal period and were more likely to be the donor twin. Gestational age at birth, gender, antenatal interventions and comorbidities did not affect long-term renal outcome between the two groups.

CONCLUSION

This is the first long-term follow-up study demonstrating that CKD progressing to the need for RRT can develop after TTTS. Donor-twin status and neonatal AKI associated with adverse long-term outcomes warranting long-term surveillance in this group.

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.

Twin-twin transfusion syndrome - What we have learned from clinical trials

Monochorionic twin pregnancies are at increased risk for adverse outcome compared to dichorionic twin pregnancies and singletons. Monochorionic-specific complications include twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence, single intrauterine fetal demise and its consequences on the co-twin, and selective intrauterine growth restriction. Whereas the natural history of monochorionic-specific complications carries a high risk of fetal death or severe neurologic disability, a framework now exists, based on well-designed clinical trials, for optimal treatment of these entities. Fetoscopic selective laser coagulation of anastomotic vessels on the chorionic plate has been clearly demonstrated to improve survival and neurologic outcomes for Quintero stage ≥2 TTTS. However, many challenges remain unsolved, the most important of which is preterm premature rupture of membranes. Further improvement in the outcomes of monochorionic pregnancies will require improvements in the rate of premature delivery, and improved diagnosis and treatment strategies for early and late onset TTTS.

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.

Fetal cardiovascular hemodynamics in twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) complicates 10-15% of monochorionic-diamniotic (MCDA) pregnancies. It originates from unbalanced transfer of fluid and vasoactive mediators from one twin to its co-twin via placental anastomoses. This results in hypovolemia in the donor and hypervolemia and vasoconstriction in the recipient twin. Consequently, the recipient demonstrates cardiovascular alterations including atrioventricular valve regurgitation, diastolic dysfunction, and pulmonary stenosis/atresia that do not necessarily correlate with Quintero-stages. Selective fetoscopic laser photocoagulation of placental vascular anastomoses disrupts the underlying pathophysiology and usually improves cardiovascular function in the recipient with normalization of systolic and diastolic function within weeks after treatment. Postnatal studies have demonstrated early decreased arterial distensibility in ex-donor twins, but 10-year follow up is encouraging with survivors showing normal cardiovascular function after TTTS. However, prediction and appropriate early management of TTTS remain poor. Assessment of the cardiovascular system provides additional insight into the pathophysiology and severity of TTTS and may permit more targeted early surveillance of MCDA pregnancies in future. It should form an integral part of the diagnostic algorithm.

Childhood cardiac outcome after intrauterine laser treatment of twin-twin transfusion syndrome is favourable

AIM

Intrauterine laser treatment is used to alleviate abnormal circulatory load and cardiac morbidity affecting foetuses with twin-twin transfusion syndrome (TTTS). We conducted this childhood follow-up study to fill the gap in knowledge about final cardiac outcomes after such interventions.

METHODS

We investigated 19 TTTS pairs - 11 male and eight female - with a mean age of four and a half years (range 1.1-9.9) using 2D, blood flow and tissue Doppler, 3D and speckle tracking echocardiography, and compared them with 19 age-matched and gender-matched singletons.

RESULTS

The only observed differences in cardiac structure or function between the donors and recipients were related to diastolic ventricular filling. Recipients had a lower left ventricular ratio of early and late diastolic filling compared with their donor cotwins [1.48(0.35) versus 1.66 (0.28), p < 0.05], but not compared with singleton controls. All observations, except one, were within the reference limits. Speckle tracking could not demonstrate any group differences in systolic ventricular function, besides marginally lower ventricular strain in the donors than controls.

CONCLUSION

Double survivors of laser-treated TTTS showed only minor within-pair differences in diastolic cardiac function at childhood follow-up. Cardiac function in TTTS twins compared well to singleton controls, suggesting a favourable long-term outcome.

Diastolic dysfunction and cerebrovascular redistribution precede overt recipient twin cardiomyopathy in early-stage twin-twin transfusion syndrome

BACKGROUND

Indications for intervention in early-stage (Quintero I and II) twin-twin transfusion syndrome (TTTS) are not standardized. Fetal echocardiography can be used to guide the management of early-stage patients. The aim of this study was to identify early cardiovascular findings that may precede progression to overt recipient twin (RT) cardiomyopathy in early-stage TTTS.

METHODS

This was a retrospective review of pregnancies evaluated from 2004 to 2010. Subjects were included when initial evaluation identified Quintero I or II TTTS without evidence of "overt" RT cardiomyopathy, defined on the basis of atrioventricular valve regurgitation, ventricular hypertrophy, and abnormal Doppler myocardial performance indices. Patients elected management with observation or amnioreduction. Pregnancies were grouped by whether the RT developed overt cardiomyopathy. Initial values, including myocardial performance index, diastolic filling time corrected for heart rate (Doppler inflow duration/cardiac cycle length), pulsatility indices of the ductus venosus, umbilical artery, and middle cerebral artery, and cerebroplacental ratio (middle cerebral artery PI/umbilical artery PI), were compared.

RESULTS

Of 174 pregnancies evaluated with early-stage TTTS, 45 (26%) did not show evidence of RT cardiomyopathy. Follow-up echocardiography identified cardiomyopathy in 20 of 45 RTs (44%). Those RTs with subsequent cardiomyopathy had shorter diastolic filling times corrected for heart rate, higher ductus venosus PIs, lower middle cerebral artery PIs, and lower cerebroplacental ratios on initial echocardiography.

CONCLUSION

Diastolic dysfunction and cerebroplacental redistribution precede findings of overt cardiomyopathy in RTs with early-stage TTTS. Assessment of these parameters may allow earlier identification of RTs with cardiac disease and help guide management. Prospective studies are needed to assess the role of echocardiography in patient selection for the treatment of early-stage TTTS.

Upper limb vascular occlusion in the recipient of a monochorionic twin pair

Monochorionicity is responsible for an increased rate of severe complications because of unequal splitting of the placental mass and/or an imbalance in the blood flow across placental vascular anastomoses. Vascular limb occlusion is one of the rare complications of monochorionic twins, usually occurring in the lower extremities after intra-uterine death of one twin, antenatal intervention (amnio-reduction or laser therapy) or in the presence of twin anemia-polycythemia syndrome. We report a case of vascular occlusion of the upper extremity in the recipient twin of a monochorionic pair in the absence of those predisposing factors.

Diagnosis and treatment of fetal cardiac disease: a scientific statement from the American Heart Association

BACKGROUND

The goal of this statement is to review available literature and to put forth a scientific statement on the current practice of fetal cardiac medicine, including the diagnosis and management of fetal cardiovascular disease.

METHODS AND RESULTS

A writing group appointed by the American Heart Association reviewed the available literature pertaining to topics relevant to fetal cardiac medicine, including the diagnosis of congenital heart disease and arrhythmias, assessment of cardiac function and the cardiovascular system, and available treatment options. The American College of Cardiology/American Heart Association classification of recommendations and level of evidence for practice guidelines were applied to the current practice of fetal cardiac medicine. Recommendations relating to the specifics of fetal diagnosis, including the timing of referral for study, indications for referral, and experience suggested for performance and interpretation of studies, are presented. The components of a fetal echocardiogram are described in detail, including descriptions of the assessment of cardiac anatomy, cardiac function, and rhythm. Complementary modalities for fetal cardiac assessment are reviewed, including the use of advanced ultrasound techniques, fetal magnetic resonance imaging, and fetal magnetocardiography and electrocardiography for rhythm assessment. Models for parental counseling and a discussion of parental stress and depression assessments are reviewed. Available fetal therapies, including medical management for arrhythmias or heart failure and closed or open intervention for diseases affecting the cardiovascular system such as twin-twin transfusion syndrome, lung masses, and vascular tumors, are highlighted. Catheter-based intervention strategies to prevent the progression of disease in utero are also discussed. Recommendations for delivery planning strategies for fetuses with congenital heart disease including models based on classification of disease severity and delivery room treatment will be highlighted. Outcome assessment is reviewed to show the benefit of prenatal diagnosis and management as they affect outcome for babies with congenital heart disease.

CONCLUSIONS

Fetal cardiac medicine has evolved considerably over the past 2 decades, predominantly in response to advances in imaging technology and innovations in therapies. The diagnosis of cardiac disease in the fetus is mostly made with ultrasound; however, new technologies, including 3- and 4-dimensional echocardiography, magnetic resonance imaging, and fetal electrocardiography and magnetocardiography, are available. Medical and interventional treatments for select diseases and strategies for delivery room care enable stabilization of high-risk fetuses and contribute to improved outcomes. This statement highlights what is currently known and recommended on the basis of evidence and experience in the rapidly advancing and highly specialized field of fetal cardiac care.

The prevalence and clinical features of twin-twin transfusion syndrome with onset during the third trimester

OBJECTIVE

To describe the incidence and clinical features of twin-twin transfusion syndrome (TTTS) with third trimester onset.

METHODS

We performed a retrospective chart review of monochorionic diamniotic (MD) twin pregnancies delivered during a recent 4-year period. The inclusion criterion was women who received prenatal care at our center from the first trimester onward. Serial ultrasound examinations were performed at least every 2 weeks until delivery to evaluate fetal growth as well as to estimate amniotic fluid volume. The prevalence of TTTS onset after 28 weeks of gestation and clinical features, including neonatal outcomes and placental findings, were elucidated.

RESULTS

Meeting our inclusion criterion were 143 MD twin pregnancies, including 15 TTTS cases (10%). Five cases (4%) developed TTTS during the third trimester and underwent a cesarean section immediately after the diagnosis. All of these women exhibited either abdominal distension or uterine contractions. Recipient twins tended to require more intensive cardiopulmonary treatment than donors, however, neither a recipient nor a donor twin suffered neonatal death or neurological impairment. Placental arterio-arterial anastomoses were detected in three out of five cases. Arteriovenous anastomoses were present in all cases, however, venovenous anastomoses were not found in any case.

CONCLUSIONS

TTTS is a relatively rare complication during the third trimester. It is imperative to be observant for the development of TTTS in MD twin pregnancies with any abdominal symptoms, even if they appear insignificant.

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

OBJECTIVE

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

STUDY DESIGN

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

RESULTS

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

CONCLUSION

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

Leptin is differentially expressed and epigenetically regulated across monochorionic twin placenta with discordant fetal growth

Severely growth-discordant monochorionic (MC) twins offer a unique opportunity to study fetal and placental growth based on a similar genetic background and maternal host environment where the healthy twin serves as an ideal control. Differences in development of MC twins may therefore be due to differential epigenetic regulation of genes involved in placental development and function. Growth-discordant twins are known for abnormal angio-architecture in the placenta of the smaller twin. Since the reasons for this phenotype are mostly unknown this study was aimed to investigate the expression and regulation of genes known to be involved in angiogenesis. We studied 10 severely growth-discordant MC twin placentas (birthweight difference ≥20%) without twin-twin-transfusion syndrome and 5 growth-concordant MC twin placentas. Growth-discordant twin placentas were phenotyped by histology. Placental mRNA expression of 88 angiogenesis-related genes was measured by PCR array. ELISA assay and immunohistochemistry were used to confirm PCR results. EpiTYPTER for DNA methylation was used to determine if methylation ratios were responsible for differential gene expression. The PCR array analysis showed significant mRNA up-regulation in the placental share of the smaller twin for several genes. These included leptin (24.6-fold, P = 0.017), fms-like tyrosine kinase 1 (Flt1, 2.4-fold, P = 0.016) and Endoglin (Eng, 1.86-fold, P = 0.078). None of the other 84 angiogenesis-related genes showed significant differences. ELISA confirmed significantly increased leptin protein expression (49.22 versus 11.03 pg/ml, P = 0.049) in the smaller twin of the discordant growth cohort. Leptin expression in smaller twins' placentas was associated with elevated DNA methylation of the leptin promotor region suggesting the inhibition of binding of a transcriptional activator/inhibitor in that region. We attempted to overcome the limitation of sample size by careful patient selection. We minimized any bias in placental sampling by random sampling from two different sites and by avoiding sampling from areas with grossly visible abnormalities using a standardized sampling protocol. In conclusion, the smaller twin's placenta is characterized by differentially increased gene expressions for Flt1 and Eng mRNA that may be causally associated with the villous pathology driven by abnormal feto-placental angiogenesis. The substantial up-regulation of leptin mRNA may be epigenetically conferred and relevant to the post-natal risk of metabolic syndrome in intrauterine growth restriction offspring with placental pathology. Growth-discordant MC twins offer unique insights into the epigenetic basis of perinatal programming.

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

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

Twin-twin transfusion syndrome

OBJECTIVE

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

METHODS

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

RESULTS AND RECOMMENDATIONS

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

Vascular limb occlusion in twin-twin transfusion syndrome (TTTS): case series and literature review

OBJECTIVE

The purpose of this study was to evaluate the phenomenon of vascular ischemic limb necrosis in twin-twin transfusion syndrome (TTTS).

STUDY DESIGN

This was a multicenter retrospective review of ischemic limb necrosis in patients with TTTS.

RESULTS

Twenty cases of fetal ischemic limb necrosis in association with TTTS were identified from 10 fetal medicine centers. The recipient was affected in 19 cases, and the lower limb was affected in 17 cases. The extent of the damage correlated with TTTS severity. Eighty percent of limb defects (16/20) clearly were unrelated to laser treatment (3 cases untreated, 7 cases after amnioreduction, 6 cases present at time of laser). The recipient was relatively polycythemic in 5 of 7 cases in which neonatal or fetal hemoglobin/hematocrit levels were available.

CONCLUSION

Ischemic limb necrosis is a rare complication of TTTS. The lesion is unrelated to therapy and may be the result of polycythemia, hypertension, and vasoconstriction.

Renin is activated in monochorionic diamniotic twins with birthweight discordance who do not have twin-to-twin transfusion syndrome

OBJECTIVE

To assess renin, aldosterone, human atrial natriuretic peptide (hANP) and brain natriuretic peptide (BNP) levels in cord blood from monochorionic diamniotic (MD) twins with a birthweight (BW) discordance that do not satisfy the criteria of twin-to-twin transfusion syndrome (TTTS).

STUDY DESIGN

Cord blood samples were obtained from 28 MD twins without TTTS. They were divided into two groups on the basis of BW discordance as follows: large (>7.5%) and small (7.5%). Cord blood renin, aldosterone, hANP and BNP levels were measured.

RESULT

Renin levels in MD twins with a large BW discordance were significantly higher than those in MD twins with a small BW discordance, with no significant differences in aldosterone, hANP and BNP levels. A significant correlation was found between renin levels and BW discordance.

CONCLUSION

Renin is activated in MD twins with a BW discordance of >7.5%, even in non-TTTS.

Twin-twin transfusion syndrome

Twin-twin transfusion syndrome (TTTS) is a serious condition that affects 10% to 15% of twin pregnancies with monochorionic diamniotic placentation. The pathophysiology of TTTS is not completely understood; however, the presence of unbalanced placental vascular communications within a shared circulation has been implicated in its development. The presentation of TTTS is highly variable, and it does not always progress in a predictable manner. Monochorionic twin gestations should, therefore, be monitored for signs of TTTS with serial sonograms starting in the second trimester. Early TTTS can be managed conservatively. However, without intervention, early-onset advanced TTTS is associated with a high perinatal loss rate and risk of severe neurologic impairment among survivors. Limited studies suggest that fetoscopic laser photocoagulation is the best available treatment for advanced TTTS diagnosed in the second trimester. Even with laser therapy, there remains a significant risk of twin demise and neurologic handicap in survivors.

Comparative expression profiles for KiSS-1 and REN genes in preeclamptic and healthy placental tissues

OBJECTIVE

The aim of the present work was to look at differences in the placental tissue expression of KiSS-1 and REN genes from preeclamptic and healthy pregnant women, that could account for a possible synergistic function for both genes in the pathogenesis of preeclampsia.

STUDY DESIGN

This case-control study involved 27 preeclamptic women and 27 normoevolutive pregnant women. cDNA was obtained from placental tissue to carry out qPCR for both KiSS-1 and REN genes in order to compare mRNA expression levels in the studied groups. Statistical analysis showed expression differences that correlate with clinical and/or biochemical variables.

RESULTS

Higher expression for KiSS-1 in PEE vs. control woman (p=0.001) was observed, whereas no difference was observed for REN expression (p=0.300) when all the subjects were included. However, REN expression was significant higher when the samples were stratified according to preeclampsia severity. For 18 mild preeclamptic patients the p-value was p=0.001 compared to their controls, while for the remaining nine with severe preeclampsia the expression became significant (p=0.001).

CONCLUSION

Our results suggest that the high KiSS-1 expression seen in preeclamptic patients is in accordance with its role as an inhibitor of trophoblast invasiveness and maintained until the end of gestation. On the other hand, aggressive therapeutic management and/or severity status of patients have a direct effect on placental REN expression levels, masking the natural high expression of this gene on preeclamptic placental tissue. Therefore it was not possible to establish a real concordant expression profile for KiSS-1 and REN genes.

Blood pressures in newborns with twin-twin transfusion syndrome

OBJECTIVE

In addition to unbalanced flow through placental anastomoses, evidence suggests that transfer of circulating vasoactive elements from the donor to the recipient contribute to the pathological process of twin-twin transfusion syndrome (TTTS). The objective of this study was to test the hypothesis that TTTS recipients have higher blood pressure (BP) at birth than donors.

STUDY DESIGN

Chart review of all TTTS infants born from 1996 to 2007 with both twins alive 24 h (51 pairs; average gestational age 30±3 weeks).

RESULTS

Both systolic and diastolic neonatal BPs were significantly higher in recipients. When expressed relative to predicted BP for birth weight (BW), BP were lower than expected in donors and higher in recipients.

CONCLUSIONS

Data indicate that TTTS recipients have BP significantly higher than donors and than BP expected for BW. The long-term impact of these early hemodynamic perturbations remains to be determined.

Twin-to-twin transfusion syndrome (TTTS)

Twin-to-twin transfusion syndrome (TTTS) is a severe complication of monochorionic (MC) twin pregnancies, characterized by the development of unbalanced chronic blood transfer from one twin, defined as donor twin, to the other, defined as recipient, through placental anastomoses. If left untreated, TTTS is associated with very high perinatal mortality and morbidity rates, due to a combination of fetal and/or obstetric complications. The reported prevalence is 10-15% of all MC twins, or about 1 in 2000 pregnancies. This consensus document reviews available evidence and offers practical guidance to clinicians by providing recommendations on various aspects concerning diagnosis and management of TTTS.

Twin-to-twin transfusion syndrome: current understanding of pathophysiology, in-utero therapy and impact for future development

Whereas monochorionic twins account for only 30% of twin gestations, they contribute to a disproportionate extent to the overall twin perinatal morbidity and mortality. Twin-to-twin transfusion syndrome can occur at any point in a monochorionic gestation but is associated with significant increases in both morbidity and mortality when it develops before 26 weeks of gestation. It is still not possible to predict accurately those pregnancies that will be affected. This has resulted in the practice of routine ultrasound surveillance beginning at the end of the first trimester. Our understanding of the physiology still has many gaps but there is an increased recognition of the heterogeneity that exists especially in the early stages of the disease. The role of the cardiovascular response of the recipient twin offers the potential for further refining the application of our current treatment modalities and may offer insight into future therapies. The optimal therapy at this point in time resides clearly with selective laser photocoagulation, and further refinements of techniques and patient selection may continue to improve outcomes. Finally, the in-utero responses generated by the fetuses to the physiologic stress of twin-to-twin transfusion may influence their response or ability to respond to cardiovascular stress in later life. If there is in-utero programming, then the detection and timely treatment of conditions such as twin-twin transfusion syndrome may have lifelong implications for both members of the twin pair.

Amniotic fluid markers of fetal cardiac dysfunction in twin-to-twin transfusion syndrome

OBJECTIVE

The objective of the study was to determine whether cardiac troponin T (cTnT) and natriuretic peptides can be isolated from the amniotic fluid (AF) of pregnancies complicated by twin-to-twin transfusion syndrome (TTTS) and whether they correlate with fetal echocardiographic findings and recipient survival.

STUDY DESIGN

AF samples from the recipient sac were obtained in 52 TTTS cases and 16 controls. Samples were assayed for cTnT and natriuretic peptides. Prior to fetoscopic laser therapy, 34 recipient twins underwent assessment of atrioventricular flow patterns, myocardial performance index (MPI), and precordial venous Dopplers. Fetal survival was assessed 48 hours postoperatively.

RESULTS

AF B-type natriuretic peptide and cTnT levels were elevated in TTTS and correlated with functional echocardiographic findings. Postoperative recipient survival was 72% when both AF-cTnT and left ventricular MPI were increased. If 1 of both markers was normal, survival was 100% (P = .046).

CONCLUSION

Combining ultrasound and AF-cTnT measurements allows the identification of fetuses at risk of postoperative demise.

Assessment of fetal cardiac function before and after therapy for twin-to-twin transfusion syndrome

OBJECTIVE

We sought to assess fetal cardiac function in monochorionic twins before and after therapy for twin-to-twin transfusion syndrome (TTTS) and compare it with control subjects.

STUDY DESIGN

We conducted prospective longitudinal assessment of fetal cardiac function in cases undergoing curative fetal therapy for TTTS (n = 39) until 4 weeks postoperatively and in uncomplicated monochorionic twins (n = 23). Fetal cardiac function was assessed by the left and right ventricular myocardial performance index, atrioventricular valve flow pattern, ductus venosus a-wave, and umbilical vein pulsations.

RESULTS

Nomograms for the myocardial performance index were constructed. Fetal cardiac function was grossly abnormal in recipient twins of TTTS when compared with control subjects (P < .001 for all indices) but normalized by 4 weeks postoperatively. The donor developed abnormal ductus venosus flow and tricuspid regurgitation postoperatively that regressed within 4 weeks.

CONCLUSION

The cardiac dysfunction in the recipient twin of TTTS normalizes within 1 month after laser. The donor develops a transient impairment of cardiac function postoperatively.