Can twin-to-twin transfusion syndrome be explained, and how is it treated?

Atypical twin-to-twin transfusion syndrome: prevalence in a population undergoing fetoscopic laser ablation of communicating placental vessels

BACKGROUND

The diagnosis of twin-to-twin transfusion syndrome (TTTS) usually relies the presence of polyhydramnios in one sac with concomitant oligohydramnios in the other sac in a monochorionic diamniotic twin pregnancy. However, TTTS does not always show a linear progression and may present with cardiac compromise or critically abnormal Doppler velocimetry in either fetus before fluid measurements meet the typically used cutoff.

OBJECTIVE

The aim of this study was to investigate the prevalence of atypical presentations of TTTS in a population undergoing laser fetoscopy.

STUDY DESIGN

We performed a retrospective review of our database of TTTS laser fetoscopy from 2003 to the present. Our center is the regional referral center in the Pacific Northwest for minimally invasive treatment of complicated monochorionic twin pregnancies. Cases were labeled as "atypical" if fluid discordance did not meet formal TTTS criteria (oligohydramnios defined as maximum vertical pocket [MVP] <2 and polyhydramnios defined as MVP >8 before 20 weeks and >10 after 20 weeks). The rationale for consideration of laser fetoscopy was other evidence of severe TTTS such as significant cardiac compromise, evidence of twin anemia polycythemia sequence (TAPS), or persistent critically abnormal cord Dopplers.

RESULTS

Three hundred seventy-nine cases of fetoscopic laser ablation for TTTS and its variants were available for review. Sixteen cases were excluded for a triplet pregnancy, 4 due to septostomy prior to referral to our center, 3 for monoamniotic pregnancy, and 11 for previous laser fetoscopy. Three hundred forty-five cases remained for evaluation. Among these, 25 cases were identified as "atypical," equaling 7.24% of our population. Eleven of these were for stage 3 recipient disease, 3 were for stage 4 recipient disease, 4 were for stage 3 both in recipient and donor, 4 were for stage 3 donor disease, and 3 were for spontaneous TAPS.

CONCLUSION

In TTTS, severity of fetal compromise does not consistently correlate with fluid abnormalities meeting established criteria. This may be especially true in rapidly progressing cases. Attempts at rigid diagnostic amniotic fluid criteria may underestimate the severity and incidence of TTTS. This underscores the importance of careful surveillance, including arterial and venous Doppler velocimetry, of all monochorionic pregnancies.

Perinatal Outcomes of Monochorionic-Diamniotic Twin Pregnancies Uncomplicated at 28 Weeks of Gestation

We examined the prevalence of specific perinatal complications of monochorionic-diamniotic twin pregnancies in cases without any abnormal findings until the second trimester of pregnancy. This was a retrospective cohort study performed at a tertiary perinatal center in Tokyo, Japan. There were 88 cases of uncomplicated monochorionic-diamniotic twin pregnancies at 28 weeks of gestation. In five of them (5.7%), there were serious complications associated with placental circulatory imbalance between the twins during the third trimester of pregnancy. Two cases were complicated by twin–twin transfusion syndrome, two cases were complicated by twin anemia–polycythemia sequence, and one case was complicated by acute twin–twin transfusion syndrome. In the five cases, no abnormal ultrasonographic findings or symptoms were recognized one or two weeks prior to the diagnosis. Fifty-eight cases (65.9%) were delivered at term uneventfully. Serious complications due to placental circulatory imbalance between twins occurred in about 6% of cases during the third trimester of pregnancy.

Clinical characteristics of monochorionic twins with large hemoglobin level discordance at birth

OBJECTIVES

To evaluate neonatal outcomes and clinical characteristics of monochorionic diamniotic (MCDA) twins with a large intertwin hemoglobin (Hb) difference at birth.

METHODS

This was a retrospective cohort study of MCDA twin gestations delivered at Osaka Medical Center and Research Institute for Maternal and Child Health between 2003 and 2012. Cases of pregnancy termination, acardiac twins or intrauterine death were excluded. A large intertwin Hb difference at birth was defined as > 8.0 g/dL according to the postnatal criteria for twin anemia-polycythemia sequence (TAPS). The intertwin reticulocyte count ratio (RCR) was calculated by dividing the reticulocyte count of the anemic twin by that of the polycythemic twin. Cases with Hb differences were divided into two groups according to the RCR, TAPS when the RCR was > 1.7 and acute fetofetal hemorrhage (AFFH) when the RCR was ≤ 1.7. Neonatal outcomes were compared between the TAPS and AFFH groups.

RESULTS

During the study period, 432 MCDA twin pregnancies of a total of 532 born at our hospital were analyzed. There were 12 (2.8%) cases of a large intertwin Hb difference. The median gestational age at birth of these cases was 34 (range, 23-38) weeks, and all were delivered by Cesarean section. There were seven (1.6%) cases of TAPS and five (1.2%) of AFFH. The neonatal survival rate was 91.7%; in one pair of twins with TAPS neonatal death occurred. All (100%) cases with TAPS and two (40%) with AFFH required blood transfusion or partial-exchange transfusion for at least one infant.

CONCLUSIONS

Although the incidence of TAPS and AFFH may be low in MCDA twins, many affected neonates required treatment for hematological abnormalities. Delivery of MCDA twins via Cesarean section does not appear to prevent AFFH, despite the absence of labor.

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.

Fetal heart rate patterns in monochorionic twins following acute twin-twin transfusion

Background. We present here 2 cases of acute twin-twin transfusion occurred during vaginal labor in monochorionic-diamniotic twin pregnancies. Case. Fetal heart rate tracings showed tachycardia in the donor twin in the first case, while they showed reassuring patterns in both twins in the second case. Conclusion. These differences in changes of fetal heart rate in the donor twins following acute twin-twin transfusion may be resulted from the differences in amount of transfusion and elapsed time.

Fetal and neonatal haematological complications in monochorionic twins

Placental vascular anastomoses are almost invariably present in monochorionic (MC) placentas. These anastomoses are the essential anatomical substrate for the development of several haematological complications in MC twins, in particular twin-to-twin transfusion syndrome (TTTS). Several forms of TTTS have been described, including chronic TTTS, acute perimortem TTTS, twin anaemia-polycythaemia sequence, acute perinatal TTTS and twin reversed arterial perfusion sequence. A significant evolution in prenatal care strategies and management options for patients with TTTS has occurred during the last decade. In chronic TTTS, endoscopic laser ablation of communicating placental vessels has led to an increase in survival rates. This review analyzes the possible pathophysiologic mechanisms involved, discusses the latest findings in diagnosis, therapy and prognosis, and focuses on fetal and neonatal haematologic complications associated with the various forms of TTTS.

Effect of inter-twin delivery interval on neonatal haemoglobin concentration

The aim of this study was to examine the effect of the inter-twin delivery interval on neonatal haemoglobin concentration. We retrospectively analysed 108 twin deliveries over a 5-year period. Chorionicity was determined by first trimester ultrasound or placental histopathology. The mode of delivery, time of delivery and cord/neonatal blood counts were recorded. A total of 88 sets of dichorionic and 20 sets of monochorionic twins were studied. There was no correlation between inter-twin delivery interval and haemoglobin difference (rho = 0.020, p = 0.857). In monochorionic twin pregnancies, there was a trend towards increasing inter-twin hemoglobin differences with prolonged delivery intervals. However, this trend did not reach statistical significance (rho = -0.303, p = 0.193). In monochorionic twins, there is a trend towards a lower haemoglobin concentration in the twin delivered second. This haemoglobin deficit appears to be related to the inter-twin delivery interval.

Prenatal cardiovascular manifestations in the twin-to-twin transfusion syndrome recipients and the impact of therapeutic amnioreduction

OBJECTIVE

We evaluated the cardiovascular pathologic condition in the recipient twin in twin-to-twin transfusion syndrome and the influence of amnioreduction.

STUDY DESIGN

Fetal echocardiograms and medical records of 54 pregnancies that were complicated by twin-to-twin transfusion syndrome were reviewed. Recipient twin right and left ventricular wall thickness, diameters, systolic and diastolic function, valve regurgitation, and structural cardiac defects were assessed at examination and after amnioreduction.

RESULTS

At examination (n = 28 pregnancies), cardiomegaly because of right ventricular and/or left ventricular hypertrophy was observed in 58% of recipient twins, and biventricular hypertrophy was observed in 33% of recipient twins, without ventricular dilation. Biventricular diastolic dysfunction was present in two thirds of recipient twins, and right ventricular systolic dysfunction and significant atrioventricular valve regurgitation was observed in one third of recipient twins. Serial assessment (n = 21 pregnancies) revealed progressive biventricular hypertrophy and right ventricular systolic and biventricular diastolic dysfunction in most recipient twins. Steeper progression of hypertrophy, diastolic dysfunction, and structural or functional right ventricular outflow disease (20% incidence) were associated with an increased perinatal mortality rate.

CONCLUSION

In twin-to-twin transfusion syndrome, the recipient twin has progressive biventricular hypertrophy with predominant right ventricular systolic and biventricular diastolic dysfunction. Despite amnioreduction, the cardiovascular disease persists and even progresses in many recipient twins.

Haemoglobin differences at birth in monochorionic twins without chronic twin-to-twin transfusion syndrome

OBJECTIVES

To determine the haemoglobin (Hb) differences at birth in monochorionic (MC) twins without chronic twin-to-twin transfusion syndrome (TTTS) in relation to birth order and placental vascular anatomy.

METHODS

All consecutive cases of MC twins without chronic TTTS and dichorionic (DC) twins delivered at our centre and admitted to our neonatal nursery between June 2002 and December 2004 were included in our study. We analysed Hb differences at birth and on day 2, in relation to birth order and placental vascular anatomy.

RESULTS

Forty-five pairs of MC twins and 71 pairs of DC twins were included. Mean Hb differences at birth in MC and DC twins were similar, respectively 1.5 and 1.4 g/dL. Hb differences >5 g/dL at birth were found in 2% (1/45) of MC twins compared to 8% (6/71) in DC twins. On day 2, mean Hb differences in MC twins increased to 3.8 g/dL, and the rate of MC twins with Hb differences >5 g/dL increased to 27% (12/45) (p < 0.001). Mean Hb differences and the percentage of twins with Hb differences >5 g/dL in DC twins did not change on day 2. In MC twins, Hb levels measured on day 2 were significantly higher in second-born twins than in first-born twins, respectively 17.7 and 15.5 g/dL (p = 0.002). Hb differences on day 2 were significantly higher in MC twins with superficial vascular anastomoses than those without superficial anastomoses, respectively 4.0 g/dL and 1.5 g/dL (p = 0.036).

CONCLUSIONS

Hb differences occur more frequently in MC twins without chronic TTTS than in DC twins, but only when measured on the second day of life. Hb differences in MC twins are associated with birth order and superficial vascular anastomoses.

Multiple birth versus neonatal brain lesions in children born prematurely as predictors of perceptuo-motor impairment at age 6

Our primary objective in this study was to test the multiple birth hypothesis, which asserts that multiple gestation and delivery, per se, entail a greater likelihood of adverse outcome than for singletons. Our second objective was to assess the power of various neonatal risk indicators to predict developmental status at school age. In particular, we sought to weigh multiple birth as an indicator of outcome against brain lesions visualized by ultrasonography. Additional neonatal indicators included birth weight, gestational age, weight relative to gestational age, and gender. At 6 years of age, children were assessed on selected aspects of perceptuo-motor competence and verbal ability. Previous findings favoring the multiple birth hypothesis have been mostly confined to comparisons of unmatched groups of twins and singletons. This study limited investigation to children born prematurely (before 35 weeks gestation) and included comparison of multiplet-singleton pairs, matched on type and extent of any lesions, gestational age, and birth weight. The full sample comprised 124 singletons and 45 multiplets (twins, triplets, and quadruplets). About half exhibited brain lesions in the neonatal period. In this population, there was no tendency for singletons to do better than multiplets, either in the unmatched or matched samples, at 6 years of age. Lesions, supplemented by gestational age, were highly predictive of outcome on the selected measures. In contrast, the multiple birth factor was of no predictive utility.

Minimal access fetal surgery

The development of fetal surgery has led to promising therapeutic options for a number of congenital malformations. However, preterm labor (PTL) and premature rupture of membranes continue to be ubiquitous risks for both mother and fetus. To reduce maternal morbidity and the risk of prematurity, minimal access surgical techniques were developed and are increasingly employed. Congenital diaphragmatic hernia (CDH), obstructive uropathy, twin-to-twin transfusion syndrome (TTTS), and sacrococcygeal teratoma have already been successfully treated using minimal access fetal surgical procedures. Other life-threatening diseases as well as severely disabling but not life-threatening conditions are potentially amenable to treatment. The wider application of minimal access fetal surgery depends on a continued improvement in technology and a better understanding of complications associated with fetal intervention.

Size-discordant twin pairs have higher perinatal mortality rates than nondiscordant pairs

OBJECTIVE

The purpose of this study was to determine whether size-discordant twin pairs have worse perinatal mortality and neonatal morbidity rates than nondiscordant pairs and whether the smaller twins of discordant pairs have worse perinatal outcomes than the larger twins.

STUDY DESIGN

We conducted a population-based, retrospective analysis of linked birth certificates and fetal and infant death certificates for 9590 twin pairs who were born in the state of Washington from 1987 through 1999. The Cochran-Mantel-Haenszel test, Student t test, and McNemar test were among the tests used to assess statistical significance.

RESULTS

Discordant twin pairs had higher rates of perinatal mortality, neonatal mortality, and 5-minute Apgar scores of <7, even after stratification by gestational age. Discordant pairs had lower pair weights at each gestational age and were more likely to include small-for-gestational-age infants. Compared with the larger twins, the smaller twins of discordant pairs had higher rates of perinatal mortality.

CONCLUSION

Discordant pairs had worse perinatal outcomes within each gestational age category.

Impact of laser coagulation in severe twin-twin transfusion syndrome on fetal Doppler indices and venous blood flow volume

OBJECTIVE

To evaluate the impact of fetoscopic laser coagulation of placental anastomoses in severe twin-twin transfusion syndrome on fetal Doppler indices and umbilical vein blood flow volume as calculated with Doppler and two-dimensional ultrasound.

METHODS

Thirty-two cases of second-trimester severe twin-twin transfusion undergoing laser therapy were examined with serial ultrasound before and 1, 3 and 5 days after therapy. Pulsatility indices in the umbilical artery and ductus venosus were measured. Blood volume flow at the level of the intra-abdominal umbilical vein was calculated by means of Doppler and two-dimensional ultrasound. The development of hydropic signs in donors was recorded. Perinatal outcome in terms of neonatal survival was recorded for all cases.

RESULTS

In recipients, ductus venosus pulsatility index decreased progressively after therapy and, by day 5, median pulsatility index was significantly lower than that before therapy (0.97 vs. 0.82, P < 0.0001). Umbilical vein blood flow volume in recipient twins showed no significant variations before and after laser. In donors, umbilical artery pulsatility index decreased significantly by the first day following therapy (2.1 vs. 1.6, P < 0.0001). Previously absent or reverse umbilical end-diastolic flow reappeared after therapy in 46% (7/15) of donors. Ductus venosus pulsatility index in donors increased significantly by day 1 after therapy (0.99 vs. 1.35, P < 0.0001) but, over days 3 and 5, it returned towards preoperative values. Umbilical vein flow volume measurements (mL/min/kg) in the donor increased by approximately 50% the day after treatment (151 vs. 232, P < 0.0001) and remained elevated. Umbilical vein flow volume before laser therapy was significantly lower in donors compared to recipients (151 vs. 260, P < 0.0001), but the difference was non-significant after treatment (240 vs. 267). One or more hydropic signs developed in eight (25%) donors during the 5 days' observation after therapy.

CONCLUSIONS

Laser therapy induced important changes in fetal hemodynamic parameters, resulting in a reversion of the disturbances associated with severe twin-twin transfusion syndrome. The recipient twin showed a progressive improvement of previous signs of right cardiac overload. The donor experienced a substantial increase in umbilical vein blood volume flow accompanied by a transitory state of relative right overload, which may explain the development of transient hydropic signs in a proportion of donors.

Rapid onset of severe twin-twin transfusion syndrome caused by placental venous thrombosis

We report a case of rapid onset of severe twin-twin transfusion syndrome (TTTS) at 25 weeks gestation in a monochorionic twin pregnancy that was uneventful before that time. Thrombosis of a main venous branch draining several arteriovenous (AV) anastomoses to the donor changed the previous hemodynamic balance that existed between multiple bidirectional AV anastomoses. The opposing AVs became hemodynamically uncompensated and, despite amnioreductions, severe TTTS developed. At 27 weeks a cesarean section was performed because of worsening cardiotocography parameters of both fetuses. Birth weights were 750 and 1840 g, and initial hemoglobin concentrations were 9.2 and 13.4 mmol/liter for donor and recipient, respectively. The recipient twin died 5 months later of an ischemic, necrotic, and perforated small intestine due to a thrombosed superior mesenteric artery. The donor is well at 2.5 years. No abnormalities in several factors associated with thrombophilia, including factor V Leiden mutations, were found in the parents.

Transient hydropic signs in the donor fetus after fetoscopic laser coagulation in severe twin-twin transfusion syndrome: incidence and clinical relevance

OBJECTIVE

To evaluate the incidence, characteristics, and impact on perinatal outcome of the development of hydropic signs in the donor fetus after laser coagulation for severe twin-twin transfusion syndrome in the second trimester.

METHODS

Forty cases of second-trimester severe twin-twin transfusion underwent fetoscopic laser coagulation of placental anastomoses and were followed up with serial ultrasound up to 14 days after therapy. Ultrasound scans were performed just before, and on days 1, 3, 5 and 14 after therapy, and fetuses were monitored for the presence of hydropic signs (skin edema, pleural effusion, ascites and pericardial effusion). Response to therapy and perinatal outcome in terms of neonatal survival were recorded for all cases.

RESULTS

Four recipients (10%) and three donors (7.5%) died over the first 72 h after therapy. During the study period, two recipients (5.5%) developed frank hydrops fetalis, and eventually died in utero. Ten donors (27.0%) developed one or more hydropic signs. In nine (90%), signs were mild or moderate and transient (mean, 3.2 days), while in one case hydrops worsened and the fetus eventually died. No donors with transient hydrops died in utero, and two died postnatally due to extreme prematurity. Gestational age at procedure and deepest amniotic fluid vertical pocket were similar between hydropic and non-hydropic donors. Discrepancy in estimated fetal weight at procedure was significantly lower in donors developing hydrops (9.6 (SD, 6.4) vs. 17.8 (14.4)%,P = 0.018). In pregnancies with hydropic donors, gestational age at delivery (33.1 (3.4) vs. 29.7 (3.5) weeks,P = 0.015) and birth weight for recipient (2392 (423) vs. 1631 (576) g, P < 0.001) and donor (1908 (774) vs. 1281 (583) g,P = 0.021) were significantly higher. The development of transient hydrops had no influence on neonatal survival at 28 days nor on the rate of clinical resolution of intertwin transfusion.

CONCLUSIONS

Transient hydropic signs may develop in a proportion of donor fetuses after laser coagulation for severe twin-twin transfusion syndrome. This phenomenon is normally not associated with a poor prognosis, and possibly indicates an hemodynamic adaptation response following interruption of the transfusion process.

Current experience with fetoscopy and the Eurofoetus registry for fetoscopic procedures

Fetoscopy has consolidated its position in fetal medicine, thanks to a combination of insight into the pathophysiology of selected conditions that are amenable to fetal surgery and the technical innovations in endoscopic equipment. In clinical practice, two types of fetoscopy can be discerned: Obstetrical Endoscopy and Endoscopic Fetal Surgery. The first involves surgical interventions on the placenta, umbilical cord and fetal membranes. Nd:YAG laser coagulation of placental vessels in case of feto-fetal transfusion syndrome and cord occlusion in monochorionic pregnancy are the most typical procedures. The second type addresses some rare fetal conditions requiring in utero surgery; most experience has been gathered with congenital diaphragmatic hernia. Endoscopic fetal surgery has a different historical and experimental background than obstetrical endoscopy, but they both share technical aspects as well as potential side effects. In this review, we aimed at bringing together currently available experience. We suggest that future developments of fetal endoscopic operations will involve a mixture of concepts from both fetoscopy types to reduce maternal invasiveness and complications, eventually improving acceptance by parents and doctors. We encourage the registration of all experience in a yet available open registry for prospective data collection, supported by the European Commission, with as primary target the assessment of maternal and fetal safety.

Trends of discordant fetal growth in monochorionic twin pregnancies

We derived simple analytical relations representing trends of discordant fetal growth in monochorionic twins developing the twin-twin transfusion syndrome from an approximation of previously developed model equations. In severe twin-twin transfusion syndrome cases, the difference between the estimated fetal weights of both twins increases proportional to (t - 5)5 (t denotes gestational age in weeks) and the sum of both weights increases proportional to t3. Hence, the ratio between the difference of estimated fetal weights and the average of the two weights (difference average ratio) increases in proportion to (t - 5)5/t3. In mild cases, the difference between estimated fetal weights as well as the sum of the two weights increases proportional to t3. Therefore, the difference average ratio becomes a constant. Comparison with clinical data of severe and mild cases showed surprisingly good agreement except after laser coagulation of placental anastomoses. These relations may therefore enable us to distinguish between severe and mild developing twin-twin transfusion syndrome cases.

Obstetrical endoscopy

Fetoscopy has been reintroduced in fetal diagnosis and therapy, as a result of instrumental innovations. It has been suggested that fetoscopy be used to guide endoscopic operations on the fetus, but this application is still in the experimental phase. Its use for surgical interventions on the placenta, umbilical cord, and to a lesser extent the fetal membranes, could be called 'obstetrical' endoscopy. Nd:YAG laser coagulation of chorionic plate vessels for feto-fetal transfusion syndrome is the most common operation carried out today. Survival rates of 60% or more have recently been reported on both sides of the Atlantic Ocean. Neurological morbidity does not exceed 6%, which compares favorably with serial amnioreductions and may become the most important incentive for performing the operation. A randomized trial comparing both therapies as a next step is being proposed. Fetoscopy has also been used for cord ligation, but because of the complexity of the operation and the high risk for preterm prelabor rupture of the membranes, other alternatives have been investigated. Most experience has been gathered with bipolar cord occlusion, a procedure which can be performed under ultrasound guidance. The instrumental considerations and potential complications of fetoscopy are discussed.