Twin Reversed Arterial Perfusion Research Articles

Monochorionic monoamniotic twins- a five year review

AimTo identify the incidence of monochorionic monoamniotic (MCMA) twins over a 5 year period in a tertiary referral centre and to assess the perinatal outcome this group.MethodsA retrospective search of...

Treatment of twin reversed arterial perfusion sequence with alcohol ablation or bipolar cord coagulation

ObjectiveTo evaluate perinatal outcome in pregnancies complicated by TRAP sequence. MethodsThe perinatal outcomes of 15 TRAP sequence pregnancies referred to Kanuni Sultan Suleyman Research and Teaching Hospital, Turkey, were evaluated. Six cases were treated conservatively. Alcohol ablation and bipolar coagulation were performed in 5 and 4 cases, respectively. ResultsIn 12 cases, there were signs of fetal compromise and acardiac/pump twin abdominal circumference ratio of more than 50%. In 3 cases without intervention, the ratio was less than 50%. Three of the 6 pregnancies treated conservatively resulted in intrauterine death of the pump twin. Alcohol ablation was successful in 3 cases, with delivery of live fetuses at 36–38weeks, whereas intrauterine death occurred in 1 case and abortion occurred in 1 case. In 2 of the cases involving bipolar cord coagulation, live birth occurred at 39weeks; preterm premature rupture of membranes and abortion occurred at 18weeks in 1 case, and pregnancy was terminated in 1 case because of ventriculomegaly. ConclusionConservative therapy is suitable for mild cases of TRAP sequence in which the pump twin dominates. If there are signs of pump twin compromise, alcohol ablation and bipolar cord coagulation can be performed successfully.

Prenatal diagnosis and outcome of multiple pregnancies with reversed arterial perfusion (TRAP-sequence)

We analyse the prenatal detection and pregnancy outcome of twin reversed arterial perfusion syndrome (TRAP-sequence) in monochorionic twin pregnancies. We included all cases in which the prenatal diagnosis of a TRAP-sequence had been established and reviewed the prenatal, obstetrical, and pathological records of the acardiac twin as well as the neonatal/pediatric records of the donor twin. Minimal follow-up for the donor twin after birth was 6 months. We detected six cases of TRAP-sequence in 412 examined monochorionic multiple pregnancies (incidence 1.46%) Mean gestational age at diagnosis was 20.4 (13.1-28.0) gestational weeks. All donor twins survived without detectable mid- or long-term sequelae. There was neither missed prenatal diagnosis nor a false-positive diagnosis of TRAP-sequence. Mean birthweight of the acardiac twins was 1,400 g (830-2800 g). There was an uneventful medical history in the maternal records of all included women. Fetal karyotype was available for 5/6 twin-pairs, all revealing a normal distribution of the chromosomes. All acardiac twins had post-mortem examination with specification of the subtypes of acardiac twin displaying 3/6 acardius acephalus, 2/6 acardius amorphus, and 1/6 acardius anceps. The antenatal diagnosis of TRAP-sequence is feasible and can be established during the first-trimester-screening. The discrimination of the adequate time to end the pregnancy, though a crucial concern, remains a challenging question. Future studies should address this topic.

ACARDIAC ANCEPS FETUS- A CASE REPORT

An interesting rare case of lethal fetopathy is described. This case is based on morphological and histological confirmation. Fetus acardius is a parasite for its vascular circulation from the donor twin. The twin reversed arterial perfusion syndrome is an extremely rare manifestation of feto-fetal transfusion in twin pregnancy where the affected twin receives retrograde vascular supply from the healthy twin. Acardiac twin syndrome is a rare complication affecting monozygotic twins where one twin fails to have normal development. In this report we present an acardiac anceps fetus seen at term gestation and delivered by caesarean section, the other twin is a healthy, well formed baby. At the time of caesarean section, the live baby was delivered first and as the placenta was extracted, the malformed fetus was attached to the chorionic plate of the same placenta. A thin cord with one vascular channel was the only communication between placenta and malformed fetus which was later delivered and collected for the study.

Klinefelter twins presenting with discordant aneuploidies, acardia, forked umbilical cord and with different gonadal sex despite monozygosity

A higher frequency of twin births in sibships of Klinefelter syndrome patients and also monozygotic or dizygotic twins, themselves being affected by Klinefelter syndrome have been noted repeatedly. To address this issue, we evaluated type and frequency of twinning among Klinefelter fetuses that we had received for autopsy within a 'Prenatal Diagnosis' program. We performed fetal autopsies, and genetic analyses on DNA extracted from stained histological slides. Among 41 prenatal diagnoses of a 47, XXY karyotype we observed four twin pairs. One was dizygotic with discordant Klinefelter and Down syndrome. Three twin pairs were monozygotic as concluded from monochorial placentation. In two monozygotic pairs one twin partner was an acardiac monster and in one of these the acardiac twin showed a female gonadal sex and missing Y-chromosomal SRY-sequences as confirmed by polymerase chain reaction. There is a high rate of twinning and twin reversed arterial perfusion sequence among our Klinefelter fetuses. Forked umbilical cords at the placental insertion site in one case allowed classification as conjoined twins in the sense of a 'funiculopagus'. Anaphase lagging or semidizygosity by second polar body twinning are proposed as explanations for the gonadal sex discordance and the excessive developmental disadvantage in the one acardiac. Problems may arise with regard to non-invasive prenatal diagnosis of aneuploidies in twin pregnancies.

Perinatal outcome of twin reversed arterial perfusion sequence: A single center's experience

Objective To report our experience of using radiofrequency ablation (RFA) to treat fetuses diagnosed with twin reversed arterial perfusion (TRAP) sequence and to evaluate the perinatal outcome of pump twins. Methods Twenty-six fetuses diagnosed with the TRAP sequence were retrospectively analyzed between July 1998 and September 2011 at Asan Medical Center. Four were lost to follow-up after diagnosis and, therefore, were excluded from further evaluation. The perinatal outcomes of pump twins were evaluated by reviewing the medical records. Results Twenty-two fetuses were diagnosed with the TRAP sequence during the study period, including 15 monochorionic-diamniotic pregnancies and four monochorionic-monoamniotic pregnancies. Three patients had triplet pregnancies. The median gestational age at diagnosis was 17.4 weeks (range, 11.0 to 27.0 weeks). Of these 22 cases, in utero RFA was performed in 11 (50%), alcohol ablation in one (4.5%) and the remaining 10 (45.5%) underwent conservative management. The median gestational age at in utero intervention was 21.0 weeks (range, 17.6 to 25.0 weeks). The overall neonatal survival rate was 77% (17 of 22). The median gestational age at delivery was 37.3 weeks (range, 30.2 to 40.1 weeks). All of the surviving infants are doing well without any complications. Conclusion For fetuses with the TRAP sequence, proper in utero treatment with RFA enables to continue the pregnancy with a good prognosis.

Fetal Hydrops in a Twin Pregnancy

A monozygotic twin diagnosed in utero with fetal hydrops of unknown etiology was severely dysmorphic and had no heart sounds upon delivery. The presentation and autopsy results led to suspicion of an acardiac twin. The complications present in the surviving twin may have been prevented with earlier diagnosis and increased awareness among healthcare providers.

350: Elevated placental vascular resistance without evidence of brain-sparing persists after treatment of twin-reversed arterial perfusion sequence

evidence of brain-sparing persists after treatment of twin-reversed arterial perfusion sequence Jodie Votava-Smith, James Cnota, Susan Gomien, Mounira Habli, William Polzin, James Van Hook, Timothy Crombleholme, Erik Michelfelder Cincinnati Children’s Hospital Medical Center, Fetal Cardiology Program, The Heart Institute, Cincinnati, OH, Cincinnati Children’s Hospital Medical Center, Fetal Care Center, Division of Pediatric General and Thoracic Surgery, Cincinnati, OH, Good Samaritan Hospital, Obstetrics and Gynecology, Cincinnati, OH, University of Cincinnati, Obstetrics and Gynecology, Cincinnati, OH OBJECTIVE: Pump twins of twin-reversed arterial perfusion (TRAP) sequence may have altered cerebrovascular tone to preserve brain oxygenation in response to highly desaturated umbilical venous return from the acardiac twin. We sought to characterize the cerebroplacental Doppler patterns in pump twins before and after therapeutic radiofrequency ablation (RFA) of the acardiac twin. STUDY DESIGN: We retrospectively reviewed pre and post-RFA echocardiograms of TRAP fetuses performed between 2/04 and 2/11. Doppler evaluation included estimation of pump twin combined cardiac output indexed for weight (CCO), and pulsatility index (PI) of the middle cerebral artery (MCA) and umbilical artery (UA). PI zscores were calculated. Paired t-tests were used to compare pre and post-RFA Doppler data. RESULTS: 35 fetuses had complete pre-RFA Doppler datasets. Mean gestational age (GA) was 20.6 / 2.5 weeks. Mean z-score for UA-PI was 2.8 / 1.1, with 80% of fetuses having UA-PI z-score 2. Mean z-score for MCA-PI was 1.0 / 1.0, including 17% of fetuses with MCA-PI z-score 2 and none with MCA-PI z-score 2. Estimated fetal weight was 5th percentile for GA in 34/35 (97%). Post-RFA Doppler data was available in 12 pump twins, with follow-up study done a median of 2 days (interquartile range 1,5) post-RFA. Following intervention, pump twin CCO decreased but there was no significant change in MCA-PI, UA-PI, or CPR (Table 1). CONCLUSION: Prior to RFA therapy, the majority of the pump twins demonstrate low CPR secondary to abnormally high UA-PI rather than low MCA-PI. These findings persist in short term follow-up after RFA, despite a significant decline in CCO indicating interventional success. These results suggest elevated placental vascular resistance, which may be due to abnormal placental vascular connections which persist after cord ablation of the acardius, versus placental vascular remodeling secondary to chronic hypoxia. Further studies to characterize the placental pathology of this condition are warranted. 351 Accuracy of fetal weight estimation by ultrasound in periviable deliveries John Ethridge, Judette Louis, Brian Mercer MetroHealth Medical Center-Case Western Reserve University, Division of Maternal Fetal Medicine, Department of Obstetrics and Gynecology, Cleveland, OH OBJECTIVE: We sought to evaluate the accuracy of fetal weight estimation (EFW) by ultrasound (US) in women delivering near the limit of viability, and to determine factors that impact this accuracy. STUDY DESIGN: Retrospective chart review was performed for women delivering between 22 0/7 and 25 6/7 weeks gestation (GA). Individual patient records were reviewed to assess if an US was performed for EFW within 7 days of delivery. If so, additional potentially relevant clinical factors were abstracted (see results) and training level of person performing the ultrasound documented. These factors were examined to determine their impact on the accuracy of EFW. EFW and birth weights (BWT) were entered into an NICHD algorithm to predict survival, and were then compared between each other. RESULTS: 100 patients meeting inclusion criteria (2/2007 8/2011) were included. The cohort was 60% African-American, with median parity 1. Mean [S.D.] maternal age was 25.9 [6.9] yrs, and BMI 30.0 [7.4] kg/m2. Mean absolute percent difference (accuracy) between EFW and BWT was 10.2% (95% CI 8.0 12.4). Linear regression analysis revealed no correlation between EFW accuracy and GA, maternal age, or BMI. While significant associations were seen between BWT and accuracy (p 0.019; 1% decrease in absolute error per 100 gm increase in BWT), and in mean % error and BWT (p 0.001, 3% overestimation of BWT per 100 gm decrease in BWT), these were not clinically meaningful. ANOVA found no difference in accuracy based on race, fetal presentation, oligohydramnios, parity, smoking, prior CD, or level of training of the examiner. Mean predicted survival for the cohort from the NICHD algorithm was 43.1% using actual BWT compared with 43.6% using EFW (p 0.91). A difference greater than 20% in predicted survival was seen in only 2 cases. CONCLUSION: EFW in periviable deliveries is affected by BWT, but estimated survival based on ultrasound EFW within 7 days of delivery is similar to that based on actual BWT.

Outcome of Twin Reversed Arterial Perfusion Sequence following Treatment with Interstitial Laser: A Retrospective Study

Objectives: To determine the outcome of twin reversed arterial perfusion (TRAP) sequence treated with or scheduled for treatment with interstitial laser therapy. Methods: This is a retrospective study on ten pregnancies diagnosed with TRAP sequence. Seven of the ten pregnancies were treated with interstitial laser therapy, and two pregnancies were scheduled for later treatment. One pregnancy was treated with fetoscopic laser ablation and excluded from analysis. The delivery reports of all pregnancies were collected, the neonatal health status recorded and the median time of delivery and the treatment to delivery interval calculated. Results: Six of seven pump fetuses in TRAP pregnancies treated with interstitial laser therapy at a median of 16+2 (range 13+1 to 20+3) gestational weeks were born healthy at a median of 38+0 (range 34+3 to 40+6) gestational weeks. One fetus treated with interstitial laser died after the procedure at 20+3 weeks. Two pump twins scheduled for later treatment died before the gestational age of 16 weeks. The median treatment to delivery interval for the surviving fetuses was 153 days (range 128-194). Conclusion: Treatment of TRAP sequence by interstitial laser therapy is feasible from the 13th week of gestation and has a good outcome.

Pregnancy Outcome of Monochorionic Twins: Does Amnionicity Matter?

To compare the fetal loss rate of monochorionic (MC) twin pregnancies according to their amnionicity. A retrospective review of all MC pregnancy outcomes in a tertiary centre. Pregnancy outcomes were compared for monochorionic monoamniotic (MCMA) versus monochorionic diamniotic (MCDA) pregnancies. 29 MCMA and 117 MCDA twin pregnancies were identified. The overall fetal loss rate was significantly higher in MCMA (23/52, 44.2%) compared to MCDA pregnancies (28/233, 12%, Chi squared = 30.03, p < .001). Kaplan-Meier analysis showed that fetal survival rate in MCDA twins were significantly higher than in MCMA twins (Log-rank Chi-squared = 27.9, p < .0005). Early pregnancy ultrasound identified the causes for these fetal losses in some MCMA twins. After exclusion of identifiable causes, the difference in fetal survival was not significant in the two groups (Log-rank chi-squared = 0.373, p = .54). The loss rate for MCMA twins is high and occurs mainly due to discordant congenital abnormality, conjoint twins or twin reversed arterial perfusion (TRAP) sequence. Although the fetal loss rate in MCDA is lower than in MCMA pregnancies, the majority of fetal loss in MCDA pregnancies cannot be predicted at the first scan at presentation. The data of this study questions the widespread policy of a difference in the scheduling of elective delivery for MCMA and MCDA twins.

Echocardiographic Risk Stratification of Fetuses with Sacrococcygeal Teratoma and Twin-Reversed Arterial Perfusion

Objective: To evaluate pre-intervention echocardiographic parameters of cardiac function in fetuses who survive without hydrops as compared to fetuses who develop hydrops or perinatal death in the setting of sacrococcygeal teratoma (SCT) and twin-reversed arterial perfusion sequence (TRAP). Methods: Clinical, echocardiographic and sonographic data of fetuses with SCT or TRAP during 1999–2009 were reviewed retrospectively. Measurements of cardiothoracic ratio (CTR), cardiac dimension Z-scores, combined ventricular output (CVO), valvular regurgitation, and cardiovascular profile scores (CVPS) were obtained. Results: In total, 19 fetuses (11 SCT, 8 TRAP) met the inclusion criteria and 26 detailed fetal echocardiographic studies were reviewed. Outcome was poor in 7 pregnancies (group A) and good in 12 (group B). Group A had worse CVPS (8.5 vs. 10, p < 0.01) and higher CTR (0.37 vs. 0.30, p = 0.04). At least one of the following was present in each group A fetus: CTR >0.5, CVO >550 ml/min/kg, tricuspid or mitral regurgitation, or mitral valve Z-score >2. No group B fetus had any of these abnormalities. No fetus in either group had abnormal venous Doppler waveforms at presentation. Conclusions: Fetal echocardiography can identify abnormalities of cardiac size and systolic, but not diastolic, function in all fetuses who subsequently died or developed hydrops.

P22.08: Persistent rudimentary cardiac activity of the perfused twin after radiofrequency ablation for twin reversed arterial perfusion sequence

A-29-year-old women, 1 para, was admitted to our institute following the diagnosis of twin reversed arterial perfusion (TRAP) sequence at 17 weeks of gestational age. Color and pulsed Doppler examination demonstrated tiny rudimentary cardiac activity of approximately 90 beats per minute (BPM) in the acardiac twin as well as arterial blood flow perfusing the acardiac twin via arterioarterial anastomosis (AAA) and venous flow in venovenous anastomoses to the pump twin. The acardiac/pump twin size ratio was 76% and the pump twin was associated with tricuspid and mitral regurgitation, cardiomegaly and hepatomegaly due to cardiac failure. Radiofrequency ablation (RFA) was performed at 18 weeks of gestation. The patient provided written informed consent and the Institutional Review Board at the institute approved. Until a confirmation of the disappearance of blood flow to the acardiac twin using HD flow of Voluson E8 (GE Healthcare, Kretztechnik, Zipf, Austria), the procedures were repeated targeting to the artery in the acardiac twin. However, just after the procedure, tiny heart beats of approximately 90 BPM and to-and-fro blood flow at aorta and a vessel of the neck were detectable in the acardiac twin with HD flow aside from fetal heart rate of 150 BPM in the pump twin. Subsequently, cardiac activity of the acardiac twin still existed 5th days after the procedure. Persistent rudimentary heart beat of the acardiac twin should be distinguished from the rest of blood flow from the pump twin after RFA for TRAP sequence.

Advances in Ultrasonic Assessment of Acardiac Twin

ABSTRACT The development of an acardiac anomaly, one of the most severe human malformations, is a rare complication unique to monochorionic multiple pregnancies. In this condition, the primary malformation is the lack of a well-defined cardiac structure in one twin (the acardiac twin), which is kept alive by its structurally normal co-twin (the pump twin). The final diagnosis for a twin pregnancy with an acardiac twin may be established after the 9th week, when the cephalic extremity and limbs can be precisely determined. Direct signs that lead to the diagnosis of an acardiac twin include the absence of cardiac and fetal movements, difficult visualization of the trunk and cephalic poles, thickening of subcutaneous tissue and the presence of umbilical artery reverse flow towards the acardiac fetus mass. The pump fetus may demonstrate hydramnios, cardiomegaly and heart failure. Once an acardiac anomaly is diagnosed, both the acardiac and pump twins should be assessed to classify the pregnancy according to prognostic factors based on the size and growth of the acardiac twin and the cardiovascular condition of the pump twin. Assessing the extent of heart damage in the pump fetus is a key step in pregnancy management. There are two available options, either conservative or interventional, for the management of these pregnancies. Serial ultrasound surveillance is important for detecting any worsening of the condition, which may suggest the need for interventions to optimize the pump-twin's chance for survival. We performed a retrospective analysis of three cases of monochorionic twin pregnancies diagnosed with a twin reversed arterial perfusion (TRAP) sequence during the first and second trimesters. We compared our data with those offered by a review of the literature.

An Acardiac Twin with Advanced Brain Development and a Minor Form of Holoprosencephaly and Intracerebral Retina-Like Pigmented Tissue: A Case Report and Review of the Literature

The development of an acardiac twin in a monochorionic multiple pregnancy is a rare and severe complication of abnormal placental vascular anastomoses. These malformed fetuses present with a very bizarre morphology and a plethora of different malformations. However, all acardiac twins show either a complete absence or an anlage of the heart. Cerebral development is usually poor. We report, according to our review of the literature, for the first time, a very unusual case of acardius with features of acardius amorphus and acormus (fused head and malformed axial skeleton without macroscopically detectable internal organs) with lobar holoprosencephaly and intracerebral pigmented retina-like tissue.

Triplet pregnancy complicated by two acardiac fetuses

Triplet pregnancy complicated by two acardiac fetuses

Feto acardio en gestación gemelar a término

Twin reversed arterial perfusion sequence (TRAP) is a serious complication of monochorionic twin pregnancies, in which one twin perfuses the other twin (an acardiac fetus) via large arterio-arterial and veno-venous anastomoses. We report a case of monochorionic twin pregnancy at term, in which the second twin was an acardiac fetus with only an undeveloped lower limb and rudimentary colonic tissue. The first twin was born healthy, a very rare outcome in this entity as the pump twin usually shows distinct degrees of cardiac overload, leading to intrauterine death from heart failure in more than 50% of cases.

Feto acardio en gestación gemelar monocorial biamniótica. Síndrome de perfusión arterial inversa gemelar

Multiple gestations involve an exacerbation of the signs and own symptoms of the pregnancy, and suppose a situation of risk for the mother as for the fetuses. One of these complications is the twin reverse arterial perfusion (TRAP), a very rare process (1% of the multiple gestations) or 0,3/10000 borned alive, that consists of the coexistence of a normal fetus (called “pump”) and an acardiac fetus. The abnormal fetus, displays, in most of the cases, incomplete development of the cephalic pole, heart, superior members and numerous organs. The lower members are relatively well conserved although the foot is usually bad conformed as well as the anomalies in the toes are frequent. Is frequent the edema in superior half of the fetus. We displayed an agreed case about this matter occurred in our hospital.

Role of prenatal fetal echocardiography in maternal medical disorders

Cardiac defects are the most common structural abnormalities seen in 8 per 1000 infants born alive. Prenatal diagnosis of a congenital cardio vascular malformation by fetal echocardiography influences the management of pregnancy, labour and delivery and post natal care. Prospective study was conducted on 180 pregnant women by fetal echocardiography at 20 weeks of gestation at Govt. R.S.R.M. Hospital, Royapuram, Chennai-13 with known risk factors for congenital heart disease in their offspring and with underlying maternal medical disorders. Four chamber view made out in 172 cases, congenital cardiac lesion were detected in 14 cases following detailed examination. Sensitivity 95.6%, Positive predictive value 92.5%, Specificity 22.2%, Negative predictive value 33.3% .Cardiac anomalies diagnosed in 18 cases diagnosed prenatally. Our sensitivity was 94%, specificity 100% positive predictive value 100%, positive negative value 91.7% .20 cases of lethal extra cardiac anomalies were detected one case of TRAP was diagnosed and in 81% cases showed normal karyotyping and 19% cases showed abnormal karyotyping. In all 20 cases of lethal anomalies termination was offered. For TRAP embolization was done for acardiac twin. 134 cases delivered vaginally, 25 cases LSCS done for obstetrics cause. Postnatal follow-up of two cases of fetus showed interventricualr septal thickness and cardiomyopathy died in utero. For VSD case autopsy done. All 11 live babies and the one case of VSD missed prenatally were referred to the cardiologist .Fetal echo is a useful noninvasive tool which can predict Fetus at Risk whenever there is underlying maternal medical disorder.

Two Major Patterns of Nongenetic Malformations Are Found at Autopsy

Patterns of malformations seen in autopsies may contribute to the understanding of their pathogenetic mechanisms. Two entities, acardiac twins (ATs) and amniotic band disruption complex (ABDC), have distinct patterns, indicating different mechanisms, namely vascular perfusion deficit and external disruption. With ATs and ABDC as model groups, this study was undertaken to see if other dysmorphic infants with the characteristic defects of these models formed distinct and numerically important groups. A total of 192 autopsies with nongenetic malformations was divided into groups including (1) those with defects found in the ATs but not in the ABDC, (2) those with defects found only in the ABDC, and (3) those with a mixture of exclusive defects from each model group. The cases followed the characteristic defects of ATs or ABDC in 20% (group 1) and 28% (group 2), respectively, forming 2 large and distinct groups; only 4% had mixed malformations (group 3). Group 1 had different characteristics from group 2 as a result of the frequent multiple malformations, often with congenital heart defects (CHDs), internal and inferior malformations. These cases were probably related to a vascular perfusion deficit. Group 2 had a majority of females and single, external, and superior defects, but it lacked CHDs and inferior malformations. These cases were likely due to external disruption. Two large and distinct groups of autopsies with nongenetic malformations were thus identified, and their mechanisms are proposed to be similar to those of the model groups.

Control study of the ultrasonography with the placental vascular casts of the acardiac twins sequence

Objective To investigate the relationship between the ultrasonography diagnosis in prenatal and the postnatal placental vascular casts of the twins reversed arterial perfusion(TRAP) sequence. Methods Six cases of TRAP sequence underwent the two-dimensional and color Doppler ultrasonography, and performed placental vascular casts after termination of pregnance. Results According to the anatomical features and ultrasonography, there were 3 cases of acardius acephalus( IV) ,2 cases of acardius anceps( II ) , and 1 case of acardius acormus( I ). In all 6 cases,there were arterio-arterial and veno-venous anastomoses at the level of the chorionic plate between the normal co-twin and the acardiac twin,these anastmosis vessels were superficial and large calibre, and the distances of the placental insertions of the umbilical cords were different,4 cases <0. 5 cm, 2 cases were 4-5 cm. In 4 cases, the vessels entered and went out of the acardiac twin were just one large umbilical artery and one large umbilical vein. In 2 cases, the umbilical artery and umbilical vein had many vascular branches in the placenta. Out of 6 cases of the pump twin, 4 cases died,and 2 cases survived. Conclusions Ultrasonography was consistent with the placental vascular casts,the contrast observing gives us new information for the further research of the special type of the vascular anastmosis and prognosis of the TRAP sequence. Key words: Ultrasonography; Twins reversed arterial perfusion sequence; Placenta; Corrosion casting