Tailored management of twin reversed arterial perfusion (TRAP) sequence

Novel autopsy and genetic findings in an acardiac twin: case report and literature review

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic twinning whereby a donor twin perfuses an acardiac twin via aberrant vascular anastomoses. The resulting paradoxical retrograde blood flow supplying the acardiac twin is oxygen-poor, leading to some of the most severe malformations encountered in humans. Though the first descriptions of acardiac twins date back to at least the 16th century, the pathophysiologic processes which underpin the development of TRAP sequence are still being elucidated. Theories on the pathogenesis of TRAP sequence include deficiencies intrinsic to the embryo and primary abnormalities of the placental vasculature. Autopsy studies continue to provide clues to the underlying pathogenesis of TRAP sequence, and the characterization of the spectrum of manifestations that can be observed in acardiac twins. Herein, we present the clinical, autopsy, and molecular findings in a unique case of TRAP sequence. Novel findings include a primitive cloaca-like structure and chromosomal aberrations involving 6q11.1 and 15q25.1.

"The Strange Case of Dr Pump and Mr Acardiac": The Twin Reversed Arterial Perfusion (TRAP) Sequence in Two Monochorionic Monoamniotic (MCMA) Twin Pregnancies-Diagnosis, Prognosis and Management: Review of Literature

The Twin Reversed Arterial Perfusion (TRAP) Sequence is an extremely rare complication of monochorionic twin pregnancies, with one severely malformed twin (the "acardiac") lacking autonomous placental blood supply and being perfused by the co-twin (the "pump"), through arterio-arterial (and sometimes also veno-venous) vascular anastomoses located on the placental surface. The prognosis is poor: mortality is 100% in the acardiac twin because of its severe malformations and about 50-55% in the pump twin, mainly due to heart failure and prematurity. So, the goal of perinatal management of the TRAP twin pregnancy is to deliver a healthy and near-term pump twin without heart failure or fetal hydrops. Intuitively, the earlier the diagnosis, the better the outcome. Herein, we report two cases of monochorionic monoamniotic (MCMA) twin pregnancies complicated by the TRAP Sequence, which are of interest since the objective of early diagnosis was achieved by means of transvaginal and 3D ultrasound, two techniques which revealed themselves as being useful to this purpose but are underused in the literature. The second aim of this study is to provide an overview of literature data about the diagnosis, prognosis establishment, and management of this rare condition, which are still debated and unclear due to negligible poor-quality evidence.

Radiofrequency Ablation and Intrauterine Transfusion in a Delayed Diagnosed Acardiac Twin Pregnancy

Twin reversed arterial perfusion (TRAP) sequence or acardiac twin is a rare and severe complication of monochorionic multiple pregnancies. Acardiac twin accounts for 10% of all TRAP sequences, which is the most morphologically developed acardius. We present an undiagnosed TRAP sequence case up to 24 weeks of gestation who underwent successful amnioreduction, radiofrequency ablation (RFA), and intrauterine transfusion (IUT). During follow-up, hydrops of surviving co-twin disappeared, and fetal heart function improved. Finally, a healthy girl weighing 2400 g was born at 36 weeks of gestation. To our knowledge, this is the first reported acardiac twin pregnancy, which requires IUT, in addition to RFA, due to late diagnosis. Therefore, this case report presents successful management options for TRAP sequence cases diagnosed late in pregnancy.

Ultrasound assessment of twin reversed arterial perfusion sequence for the prediction of adverse pregnancy outcomes in the first trimester

OBJECTIVE

To investigate twin reversed arterial perfusion (TRAP) sequence for the prediction of TRAP-related adverse pregnancy outcomes at the gestational age of 11-14 weeks.

METHODS

Pregnant women in the first trimester diagnosed with TRAP were recruited at West China Second University Hospital from January 2015 to June 2018. Systematic screening for the pump twin's crown-rump length (CRL) and acardiac twin's upper pole-rump length (URL) was conducted using ultrasonic detection. The (CRL - URL)/CRL and URL/CRL ratios were used to assess the pregnancy outcomes for the pump twin. Twenty-one pregnant women aged 21-39 years with a gestation of 11-14 weeks were recruited.

RESULTS

TRAP was diagnosed on average (± standard deviation (SD)) at pregnancy week 13.1 ± 0.18. The pump twins' mean (± SD) CRL was 6.65 ± 1.1 cm. The incidence of intrauterine death for the pump twins was 19.0% (n = 4), the miscarriage rate was 14.3% (n = 3), and the live birth rate was 66.7% (n = 14). The (CRL - URL)/CRL ratios between the nonsurvival (intrauterine death and miscarriage) and survival groups significantly differed (0.33 ± 0.08 vs. 0.58 ± 0.08, p < 0.05). Similarly, the URL/CRL ratios between the nonsurvival and survival groups significantly differed (0.67 ± 0.08 vs. 0.42 ± 0.08, p < 0.05).

CONCLUSION

The (CRL - URL)/CRL and URL/CRL ratios were valuable indicators for determining pregnancy outcomes of pump twins with TRAP at an early gestational age.

Excellent perinatal outcome of monoamniotic twin pregnancy with timely diagnosis and optimal management - a retrospective cohort study

OBJECTIVES

Monoamniotic twins represent a high-risk pregnancy requiring intense follow-up, elective birth and careful consideration of the mode and timing of delivery. We conducted this study to evaluate the perinatal and neonatal outcomes of monoamniotic twin pregnancies in the largest tertiary hospital in Finland.

METHODS

This was a retrospective cohort study including all monoamniotic twin pregnancies during a 17-year period (2002-2018) managed in Helsinki University Hospital. Data on mothers and children were collected from patient files. Chorionicity and amnionicity were defined in first-trimester ultrasound screening.

RESULTS

There were altogether 31 monoamniotic twin pregnancies during the study period, including four cases of conjoined twins which all underwent termination of pregnancy, and three miscarriages. In the remaining 24 pregnancies that continued past 24 weeks of gestation there was 97.9% survival (one intrauterine death). Three pregnancies were complicated with twin-to-twin transfusion syndrome. All children were delivered by cesarean section with a mean gestational age of 32 + 5 weeks (27 + 1-34 + 2 weeks). Respiratory distress syndrome (RDS) was observed in 57% (27/47) of neonates and grade I-II intraventricular haemorrhage (IVH) in 6.3% (3/47) of neonates. There were no neonatal deaths and no maternal complications.

CONCLUSIONS

Monoamniotic twinning is a rare form of pregnancy and carries risks for perinatal and neonatal complications. With timely diagnosis, close monitoring in specialized feto-maternal unit and elective delivery at 32-34 weeks the outcome is usually excellent.

Monochorionic monoamniotic twin pregnancies

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

Morphology, intrafetal vascular pattern, and umbilical artery Doppler indices of acardiac twins

BACKGROUND

Twin reversed arterial perfusion (TRAP) sequence consists of acardiac twin (A) paradoxically perfused by pump twin (P) through an umbilical artery (UA). We proposed characterization of acardiac twins with intrafetal vascular pattern (IVP), and assessed its correlation with morphology and UA Doppler indices.

METHODS

We prospectively evaluated 21 cases of TRAP sequence. Morphology (acardia vs hemicardia) and IVP (simple vs complex) of acardiac twins were characterized with ultrasound and color Doppler. Twins weight ratio (A/P Wt) and UA Doppler indices of acardiac and pump twins including (1) difference of systolic/diastolic ratio (UA ∆S/D), (2) difference of resistance index (UA ∆RI), and (3) ratio of pulsatility index (UA PI A/P) were calculated.

RESULTS

The median (min, max) gestational age at diagnosis was 18 (11, 27) weeks. Acardia (n = 14) were associated with simple IVP (n = 16) (P < .05). After exclusion of acardia with complex IVP (n = 1), the A/P Wt, UA ∆S/D, UA ∆RI, and UA PI A/P of acardia with simple IVP (n = 13), hemicardia with simple IVP (n = 3), and hemicardia with complex IVP (n = 4) were not significantly different (P > .05).

CONCLUSIONS

Most of acardiac twins were acardia with simple IVP. Morphology and IVP of acardiac twins were not associated with UA Doppler indices.

TRAP Sequence in Monochorionic/Monoamniotic (MC/MA) Discordant Twins: Two Cases Treated with Fetoscopic Laser Surgery

INTRODUCTION

Ablation of the acardiac twin umbilical cord in the TRAP protects the normal donor twin.

MATERIALS AND METHODS

Two case descriptions, one of interstitial laser photocoagulation and one of laser umbilical cord occlusion (L-UCO) of the acardiac twin in monochorionic monoamniotic pregnancies are reported.

RESULTS

L-UCO in two pregnancies with TRAP syndrome in the second trimester resulted in intrauterine fetal death in both cases after 1 month. Case 1 had no detectable cause of fetal death. Case 2 had rupture of the amniotic sac causing anhydramnios and acute chorioamnionitis. A groove on the umbilical cord of the normal twin indicated a cord stricture due to cord entanglement.

CONCLUSION

Our experience confirms that the best timing and optimal treatment of MC/MA twins complicated by TRAP sequence still remains a controversial clinical issue. Cord entanglement may continue be a potential clinical risk factor for adverse perinatal outcome even after ablation therapy.

First-trimester intervention in twin reversed arterial perfusion sequence: does size matter?

OBJECTIVE

To evaluate the outcome of first-trimester intervention (12 + 0 to 14 + 0 weeks of gestation) in pregnancies complicated by twin reversed arterial perfusion (TRAP) sequence.

METHODS

All monochorionic diamniotic twin pregnancies diagnosed with TRAP sequence that underwent intrafetal laser ablation (IFL) of the feeding vessels before 14 + 0 weeks of gestation at the University of Bonn between 2010 and 2015 were analyzed retrospectively for intrauterine course and outcome.

RESULTS

In the study period, 12 pregnancies with TRAP sequence were treated by IFL. Median gestational age at intervention was 13.2 (interquartile range (IQR), 12.6-13.6) weeks. In all cases, one intervention sufficed to disrupt the perfusion of the TRAP twin. There was no case of miscarriage, preterm prelabor rupture of membranes or hemorrhage. In five (41.7%) pregnancies, intrauterine death of the pump twin occurred at a median of 72.0 (IQR, 54.0-90.0; range, 48-96) h after intervention. The remaining seven pregnancies continued uneventfully resulting in birth of a healthy infant at term. A comparison of survivors and non-survivors identified a significant difference in median discordance between crown-rump length (CRL) of the pump twin and upper pole-rump length (URL) of the TRAP twin ((CRL - URL)/CRL ratio, 0.56 vs 0.31; P < 0.05 and URL/CRL ratio, 0.44 vs 0.68; P < 0.05). Survivors were treated at a significantly later gestational age than were non-survivors (median, 13.4 (IQR, 12.9-14.1) vs 12.6 (IQR, 12.5-13.1); P < 0.05). However, none of these parameters independently predicted survival.

CONCLUSIONS

Although technically feasible, IFL performed in the first trimester for TRAP sequence is associated with a significant fetal loss rate. Gestational age at intervention, (CRL - URL)/CRL ratio and URL/CRL ratio are potential predictors of pregnancy outcome. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

[Role of twin reversed arterial perfusion syndrome in the development of fetus acardius]

Monochorionic multiple pregnancy has a higher risk for obstetric complications, including those due to the development of twin-to-twin transfusion syndrome and reversed arterial perfusion syndrome (TRAP sequence). The latter occurs in 0.1% of all monochorionic pregnancies. The basis for TRAP sequence is a relationship between arterial and venous anastomoses from the appropriate placental areas, causing a recipient fetus to develop at the expense of a donor fetus. The presence of abnormal anastomoses is considered to be a main cause of acardia. The prognosis for a donor fetus is also unfavorable: the mortality rates in the absence of intrauterine correction are as high as 55%.

Intervention versus a conservative approach in the management of TRAP sequence: a systematic review

OBJECTIVE

In the management of twin reversed arterial perfusion (TRAP) sequence, we wished to (i) determine if intervention is better than a conservative approach and (ii) assess if any of the apparent adverse prognostic indicators could guide intervention.

METHODS

A systematic review was conducted between 1994 and 2014. Data extracted were inspected for heterogeneity. Overall rates and confidence intervals (CIs) for each prognostic factor were calculated. Where there were comparative data, the odds ratio (OR) was calculated.

RESULTS

Twenty-six studies were included in the review. When all cases were considered, intervention either by cord occlusion or by ablation conferred a better survival rate compared with conservative management (OR=2.22, 95% CI 1.23-4.01, heterogeneity I2=37%, P=0.008). This difference was greater in the presence of one or more poor prognostic features (OR=8.58, 95% CI 1.47-49.96, heterogeneity I2=0%, P=0.02). Survival was better using ablative techniques compared to cord occlusion (OR=9.84, 95% CI 1.56-62.00, heterogeneity I2=0%, P=0.01).

CONCLUSION

Intervention either by cord occlusion or by ablation confers a better survival rate compared to conservative management. This appears more compelling if there are one or more poor prognostic features. Ablative techniques are superior to cord occlusion. There were insufficient data to determine which poor prognostic features should guide management.

Radiofrequency Ablation with an Internally Cooled Electrode for Twin Reversed Arterial Perfusion Sequence

OBJECTIVE

The study aims to evaluate the efficacy of radiofrequency ablation (RFA) with an internally cooled electrode for twin reversed arterial perfusion (TRAP) sequence.

METHODS

From April 2008 through December 2014, we retrospectively reviewed all patients who underwent RFA with an internally cooled electrode for TRAP sequence at 3 tertiary referral centers in Japan.

RESULTS

Twenty-five monochorionic diamniotic twin pregnancies underwent RFA with an internally cooled electrode for TRAP sequence at 16-27 weeks of gestation. In all cases, umbilical cord blood flow cessation in the acardiac twin was confirmed by ultrasonography with color Doppler. There were 2 cases of procedure-related complications: 1 case of unintentional septostomy and 1 case of anemia in a pump twin. Fetal demise of the pump twin occurred in 3 (12%) cases. Twenty-two (88%) of 25 pump twins were delivered alive. The median gestational age at delivery was 36 + 3 weeks (range 25 + 2-40 + 5 weeks). There were 14 cases (64%) of premature deliveries before 37 weeks and 5 (23%) before 32 weeks.

CONCLUSION

RFA with an internally cooled electrode is a feasible and effective procedure for the treatment of TRAP sequence.

Conservative management in a case of uncomplicated trap sequence: a case report and brief literature review

INTRODUCTION

twin reversed arterial perfusion (TRAP) sequence is a rare anomaly that occurs in monochorionic twins with overall mortality rate ranging from 50% to 70% in the normal fetus, above all for congestive cardiac failure.

CASE REPORT

a 31-year-old Caucasian gravida was referred to our fetomaternal medicine unit in the 25 gestational age. Ultrasound examination revealed a monochorionic, biamniotic twin pregnancy with a donor fetus showing normal morphology and growth corresponding to gestational age. The recipient twin appeared grossly abnormal with no head, upper limbs, heart, or thoracic structures and massive, diffuse, soft tissue edema. Fetal Doppler and fetal echocardiography revealed normal parameters. The patient refused any treatment and was monitored with weekly ultrasonography and Doppler ultrasound examination. She underwent cesarean section due to premature labor/rupture of membranes secondary to a mild polyhydramnios, at 36 weeks gestational age and delivered an apparent normal female live baby weighing 2550 gr, and another female acardius acephalus twin, birth weight 1300 gr. This baby had rudimental edematous lower limbs, pelvic bone, lower sacral vertebrae, and absence of thorax and cephalic structures.

CONCLUSION

although the literature suggest that early intrafetal laser treatment of TRAP sequence is advantageous, our case shows that pregnancies referred late would still require a tailored approach after a risk-benefit assessment.

Early vs late intervention in twin reversed arterial perfusion sequence

OBJECTIVE

To compare two different management approaches in prenatally diagnosed twin reversed arterial perfusion (TRAP) sequence.

METHODS

Retrospective analysis of all cases with TRAP sequence diagnosed in one center over a period of 10 years. Prior to 2010, all cases were managed expectantly until 19 weeks' gestation; thereafter, patients could choose either radiofrequency ablation (RFA) or expectant management (Group A). From 2010 onward all patients were offered interstitial laser at the time of diagnosis (12 weeks at the earliest) or expectant management (Group B).

RESULTS

Forty cases were included in the study. In Group A, 23 cases were diagnosed at a mean gestational age of 19.9 ± 6.3 weeks. Sixteen patients were managed expectantly (13 survivors, 81%), while six underwent RFA at the time of diagnosis and one later in pregnancy (six survivors, 86%). In Group B, 17 cases were diagnosed at a mean gestational age of 16.4 ± 4.7 weeks. Six patients chose expectant management (five survivors, 83%) and 11 had interstitial laser therapy at the time of diagnosis (eight survivors, 73%). The loss rate of the pump twin was not significantly different between Group A and Group B (three of 23 vs four of 17; P = 0.3). In Group B the rates of preterm premature rupture of membranes (PPROM) and delivery < 34 weeks were significantly lower, and gestational age at birth as well as birth weight were significantly higher than in Group A.

CONCLUSION

Despite the limitations resulting from its retrospective design, our study on management of TRAP sequence adds some evidence in favor of prophylactic intervention by intrafetal laser from 12 weeks onward.

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.

Intrafetal laser treatment for twin reversed arterial perfusion sequence: cohort study and meta-analysis

OBJECTIVES

To ascertain the outcome of twin reversed arterial perfusion (TRAP) sequence cases managed in our unit and to review systematically cases reported in the literature treated with intrafetal laser therapy.

METHODS

This was a retrospective cohort study of all TRAP sequence cases identified from 2000 to 2012 at our center. Pregnancy management and outcomes were ascertained from maternal and neonatal records. We also performed a meta-analysis of the literature on the use of intrafetal laser therapy for the treatment of TRAP. Adverse pregnancy outcome was defined as a composite of intrauterine death (IUD) and preterm birth before 37 weeks' gestation.

RESULTS

Twenty-three cases of TRAP were identified during the study period. Six were managed conservatively and 17 were treated with laser therapy. All cases managed conservatively were complicated by IUD at a median gestational age of 14 + 4 (interquartile range (IQR), 12 + 4 to 16 + 5) weeks. Among the treated cases, 14 (82%) delivered a healthy twin at a median gestational age of 37 + 1 (IQR, 34 + 0 to 38 + 3) weeks. Ten studies were reviewed in detail and the data were combined with those from the current study. The overall neonatal survival was 80%. Adverse pregnancy outcome was significantly lower when the treatment was performed before 16 weeks' gestation (19 vs 66%, P = 0.0025).

CONCLUSION

The study data demonstrate a high risk of spontaneous fetal demise in early pregnancy, lack of accurate prognostic markers and improved pregnancy outcome after laser therapy in cases of TRAP. In these cases we recommend elective treatment with intrafetal laser therapy at between 13 and 16 weeks' gestation.

[Multifoetal pregnancies complicated by reversed arterial perfusion: report of four cases]

INTRODUCTION

Twin reversed arterial perfusion syndrome (TRAP) or acardiac anomaly presents a rare and severe complication affecting monochorionic multiple pregnancies occurring in 1 per 35,000 pregnancies or 1 per 100 of monozygotic twins. We report four cases of multiple pregnancies with TRAP diagnosed over the last 2 years, which were under check-up and treatment during the entire pregnancy course finalized by delivery.

OUTLINE OF CASES

In two cases pregnancies were trigeminal, and other two geminal, with acardia of one foetus, by anceps type in three and acephalus in one. Expectant management was initially done in all cases. The relation of acardiac and donor abdominal circumference was below 50% and negative signs of the donor's cardiac failure were detected in two cases, so that expectative management was continued until delivery. Due to obstetric indications, a cesarean section was performed on the 33rd and 34th gestational week, and healthy newborns were delivered. Another two acardiac twins had abdominal circumference ratio between the acardiac fetus and the donor of over 50%, and signs of congestive heart failure in the donor, which indicated invasive therapeutic procedure with absolute alcohol chemisclerosis; it was done by alcohol injection into the acardiac abdominal aorta which interrupted the retrograde blood-flow into the acardiac umbilicus. In the first case a successful intervention was performed at 29th gestational week, but after 12 hours distress signs were registered. The delivery was finalized by a cesarean section, and a live donor was delivered. In the second case the intervention was successfully done at the 20th gestational week, and after 96 hours from the intervention lethal ending of the donor was registered.

CONCLUSION

Bearing in mind that the occurrence of TRAP is rare, it is necessary to sum-up experiences from a larger number of centres to determine efficient therapeutic procedure.

MRI findings in multifetal pregnancies complicated by twin reversed arterial perfusion sequence (TRAP)

BACKGROUND

Twin reversed arterial perfusion sequence (TRAP) is a rare complication in multifetal monochorionic pregnancies in which a normal "pump" twin provides circulation to an abnormal acardiac co-twin, resulting in high-output cardiac dysfunction in the pump twin.

OBJECTIVE

To define fetal MRI findings of TRAP sequence.

MATERIALS AND METHODS

Fetal MR images were retrospectively reviewed in 35 pregnancies complicated by TRAP sequence. Abnormalities of the pump twin, acardiac twin, umbilical cord, placenta and amniotic fluid were reviewed.

RESULTS

Acardiac twins were classified as: acephalus (51%), anceps (40%), amorphus (9%), acormus (0%). Common findings in acardiac twins include subcutaneous edema (77%), absent cardiac structures (86%), absent or abnormal thoracic cavity (100%), abnormal abdominal organs (100%), superior limbs absent (46%) or abnormal (51%), and inferior limbs present but abnormal (83%). There were pump twin findings of cardiac dysfunction in 43% and intracranial ischemic changes in 3%. Umbilical cord anomalies were present in 97%.

CONCLUSION

Acardiac twins present with a predictable pattern of malformation with poorly developed superior structures, more normally formed inferior structures and absent or rudimentary heart. Although usually absent, abnormal heart structures can be seen and do not exclude TRAP sequence. Pump twins are commonly normal with exception of findings of cardiac dysfunction and possible brain ischemia.

[Discordant anomaly in twin pregnancy]

The risk of fetal loss is multiplied by 4 in monochorionic pregnancies by comparison with dichorionic one. The incidence of selective growth retardation (sIUGR) is between 12.5 to 25%. This variation is explained by the mixture between pure twin-to-twin transfusion syndrome (TTTS) and pregnancies without TTTS but with a pure sIUGR. The ability to diagnose prenatally sIUGR is low; the positive predictive value is only 37% (EL4). The umbilical flow velocity waveforms with absent diastolic flow (Type II) or with diastolic intermittent flow (Type III) is clearly a strong risk factor of mortality of the IUGR and also a risk factor of leucomalacia of the bigger fetus (EL3). The observed incidence of malformations in twins is 4.05% versus 2.38% for singletons (OR=1.7 [IC 95% 1.47-1.97]). Furthermore, the rate of fetal malformations is higher in monochorionic pregnancies by comparison with dichorionic one, 6.33% versus 3.43% (OR=1.8 [IC 95% 1.3-2.5]) (EL3). In the majority of the cases, the malformation is concerning only one fetus. The most frequent malformations are those of the central nervous system by comparison with singletons, those of the urinary tract and the cardiovascular malformations. Monozygotic pregnancies are not necessarily phenotypically and genetically identical. In situation of asymmetrical malformation, it is necessary to propose fetal karyotype of the malformed fetus. In case aneuploidy of the malformed fetus, secondarily it will be necessary to explore the other apparently normal one. Uniparental disomy should be suspected in such situation (EL3). In TRAP sequence, an intensive follow up should be organised with serial measurement of the respective size of the acardiac fetus and the normal one, Doppler exploration should be done to look for early sign of cardiac decompensation (expert viewpoint). In dichorionic pregnancies, when the malformation is threatening the whole pregnancy like anencephaly, a selective feticide allow a prolongation of the pregnancy, but with a risk of fetal loss of 8% and a risk of iatrogenic prematurity of 12%. In such situation, it could be wise to evaluate the evolution or to wait until the third trimester to undergo the procedure (EL3). In monochorionic pregnancies, in the same situation of anencephalic fetus the best option is bipolar cord coagulation. The result seems to be better after 18 weeks of gestation (EL4). There is a 20% risk of premature rupture of membrane. In the up to date analysis of the literature, there is no formal indication of selective feticide expect case of TRAP sequence with cardiac decompensation of the normal fetus. The very special situation of sIUGR is the object of a randomized trial. In all cases the active participation of the patients to the therapeutic option is mandatory (expert viewpoint).

The role of fetal echocardiography in fetal intervention: a symbiotic relationship

In this review, the authors explore the role of noninvasive and invasive fetal interventions in fetal cardiovascular disease guided by observations at fetal echocardiography. They first review fetal cardiac lesions that may be ameliorated by fetal intervention and then review noncardiac fetal pathologic findings for which fetal echocardiography can provide important insight into the pathophysiology and aid in patient selection for and timing of intervention and postintervention surveillance.

Interstitial laser therapy for fetal reduction in monochorionic multiple pregnancy: loss rate and association with aplasia cutis congenita

OBJECTIVE

To evaluate experience with interstitial laser therapy for intrafetal vascular ablation in monochorionic (MC) multiple pregnancy.

METHODS

MC pregnancies that underwent fetal reduction between 1998 and 2007 by interstitial laser therapy were reviewed. Indications were twin reversed arterial perfusion sequence (TRAP) (n = 10), twin-to-twin transfusion (6), discordant abnormality (7) or growth (1) and high-order multiples (6).

RESULTS

Thirty pregnancies treated at 15 weeks (median, range: 11 weeks-20 weeks, 5 days) had no technical failures but four manifested procedure-related amniorrhexis. Four of 38 remaining fetuses suffered intrauterine death (IUFD) within 24 h, giving an early procedure-related fetal loss rate of 10% per pregnancy and 11% per fetus. A further five IUFDs occurred within 2 weeks, giving a maximum procedure-related loss rate of 27% per pregnancy and 24% per fetus. Median gestation at delivery was 37 weeks (18 weeks, 1 day-41 weeks, 3 days) for pregnancies continuing > 2 weeks. Perinatal survival was 26 of 38 (68%) in nonreduced fetuses. Two of 26 neonates (8%) were diagnosed with aplasia cutis congenita (ACC).

CONCLUSION

Interstitial laser therapy in complicated MC pregnancies carries significant risks of unintended fetal loss and may be associated with ACC.

Delayed structural development in an acardiac fetus: an echographic observation

INTRODUCTION

Twin reversed arterial perfusion (TRAP) is a rare condition in monozygotic multiple gestations, caused by the formation of large arterio-arterial anastomoses. Only few serial ultrasound observations are reported, showing the delayed development in the recipient twin.

CASE

A monochorionic monoamniotic twin pregnancy with discordant growth was diagnosed at 11 weeks and 4 days in a 28-year-old primigravida. The smaller twin, who first appeared as an amorphic mass, showed growth and developed a clearly recognizable spine and lower limbs in further ultrasound examinations.

CONCLUSION

This case illustrates that developmental arrest in acardiac fetuses does not affect the total organism at one time, but that some embryonic fields keep on developing into macroscopically recognizable structures.

Intrafetal radiofrequency ablation for twin reversed arterial perfusion (TRAP): a single-center experience

OBJECTIVE

The objective of the study was to review perinatal outcomes in pregnancies treated with intrafetal radiofrequency ablation (RFA) for twin reversed arterial perfusion (TRAP) sequence.

STUDY DESIGN

Perinatal outcome data from a quaternary care referral center were abstracted from a chart review of pregnancies with TRAP sequence treated in the midtrimester with umbilical cord RFA of the perfused twin.

RESULTS

Twenty-one pregnancies with TRAP sequence were evaluated. Two women had a pump twin demise prior to therapy, 1 with trisomy 21 declined treatment. Four of 20 were treated successfully with RFA but remain undelivered, and 1 was treated with fetoscopic cord coagulation. Twelve of 13 pump twins treated with RFA (94%) survived to 30 days of life. Mean preoperative cardiac combined cardiac output was 588 mL/kg and pump/twin ratio was 0.7 (range 0.4 to 1.1). The effect of RFA on postoperative cardiac output was variable (6-85%). The average gestational age at birth was 37 weeks (range 26-39 weeks).

CONCLUSION

Primary therapy with RFA is a successful modality for pregnancies complicated by TRAP sequence.

Twin reversed arterial perfusion: fetoscopic laser coagulation of placental anastomoses or the umbilical cord

OBJECTIVE

To assess the feasibility and outcome of fetoscopic laser coagulation in pregnancies with twin reversed arterial perfusion (TRAP) sequence.

METHODS

In a prospective multicenter study, percutaneous fetoscopic laser coagulation of placental anastomoses (n = 18) or the umbilical cord of the acardiac twin (n = 42) was performed in 60 consecutive pregnancies at a median gestational age of 18.3 (range, 14.3-24.7) weeks under local or locoregional anesthesia.

RESULTS

Vascular coagulation with arrest of blood flow was achieved in 82% (49/60) of cases by laser alone and in a further 15% (9/60) by laser coagulation in combination with bipolar forceps. The overall survival rate of the pump twin was 80% (48/60). Median gestational age at delivery was 37.4 (range, 23.7-41.4) weeks and the median interval between the procedure and delivery was 18.2 (range, 1.1-25.7) weeks. Median birth weight was 2720 (range, 540-3840) g. Preterm premature rupture of membranes before 34 weeks' gestation occurred in 18% (11/60) at a median of 62 (range, 1-102) days after the procedure. However, only two (3%) women delivered within 28 days of the procedure.

CONCLUSIONS

Fetoscopic laser coagulation of placental vascular anastomoses or the umbilical cord of the acardiac twin is an effective treatment of TRAP sequence, with a survival rate of 80%, and 67% of pregnancies with surviving pump twins going beyond 36 weeks' gestation without further complications.

Surgical management of twin reversed arterial perfusion sequence

OBJECTIVE

The purpose of this study was to review our experience in the management of twin reversed arterial perfusion sequence to derive management recommendations.

STUDY DESIGN

All patients with twin reversed arterial perfusion sequence who were seen for consultation between 1993 and 2004 were studied. Criteria for umbilical cord occlusion included abdominal circumference of the twin reversed arterial perfusion fetus that was more than or equal to the pump twin, polyhydramnios (maximum vertical pocket > or = 8 cm), abnormal Doppler studies or hydrops of the pump twin, or monoamniotic twins. Various surgical and access techniques for umbilical cord occlusion were used as they were developed.

RESULTS

Seventy-four patients with twin reversed arterial perfusion sequence were studied. Sixty-five patients were considered surgical candidates, of which 51 patients underwent umbilical cord occlusion attempt. The overall perinatal survival for surgical candidates who had umbilical cord occlusion was 65% (33/51 patients) versus 42.9% (6/14 patients) for the surgical candidates who did not undergo umbilical cord occlusion (P = .1). However, perinatal outcomes in surgical patients were significantly better than expectantly treated surgical candidates if the dividing membrane was not disrupted purposely (22/28 patients; 78.5%; P = .02). Surgery within the sac of the twin reversed arterial perfusion fetus was feasible in 23.5% of patients and was associated with no incidence of premature rupture of membranes, with 83% perinatal survival, and with a significantly greater gestational age at delivery (36 weeks). There were no significant differences in perinatal outcome relative to the specific surgical technique that was used.

CONCLUSION

Surgical management of twin reversed arterial perfusion sequence is indicated in high-risk patients. The surgical approach and the surgical technique should be tailored to the specific clinical presentation, preferably by performing the surgery within the sac of the twin reversed arterial perfusion sequence fetus and avoiding disruption of the dividing membrane.

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

Abstract Endoscopic laser ablation of placental vessels is the most commonly performed fetal operation today. Herein, we review the pathophysiology of twin-to-twin transfusion syndrome and the challenges of its treatment. Pediatric surgeons, with their knowledge of fetal and congenital pathology, and their technical expertise with minimally invasive surgery, can be of great benefit to the patient and the medical team.

Monochorionic twin pregnancies

The monochorionic placenta should be considered a developmental malformation and, as such, represents one of the most common birth defects. Great strides are being made to unravel the progression of nature's successful attempt at human cloning through fission. Critical to any strategy to reduce the perinatal morbidity and mortality associated with monochorionic placentas is early detection. Intense surveillance in at risk pregnancies will provide a better understanding of their natural progression, improve the prognosis with early intervention, and ultimately provide the key to prevent many of the complications unique to the monochorionic placenta.

Ultrasound in multiple gestations: twins and other multifetal pregnancies

Ultrasound has an important role not only in assessing amnionicity and chorionicity but also in diagnosing abnormalities and providing fetal surveillance throughout the duration of gestation.