Placental vessel segmentation and registration in fetoscopy: Literature review and MICCAI FetReg2021 challenge findings

Fetoscopy laser photocoagulation is a widely adopted procedure for treating Twin-to-Twin Transfusion Syndrome (TTTS). The procedure involves photocoagulation pathological anastomoses to restore a physiological blood exchange among twins. The procedure is particularly challenging, from the surgeon's side, due to the limited field of view, poor manoeuvrability of the fetoscope, poor visibility due to amniotic fluid turbidity, and variability in illumination. These challenges may lead to increased surgery time and incomplete ablation of pathological anastomoses, resulting in persistent TTTS. Computer-assisted intervention (CAI) can provide TTTS surgeons with decision support and context awareness by identifying key structures in the scene and expanding the fetoscopic field of view through video mosaicking. Research in this domain has been hampered by the lack of high-quality data to design, develop and test CAI algorithms. Through the Fetoscopic Placental Vessel Segmentation and Registration (FetReg2021) challenge, which was organized as part of the MICCAI2021 Endoscopic Vision (EndoVis) challenge, we released the first large-scale multi-center TTTS dataset for the development of generalized and robust semantic segmentation and video mosaicking algorithms with a focus on creating drift-free mosaics from long duration fetoscopy videos. For this challenge, we released a dataset of 2060 images, pixel-annotated for vessels, tool, fetus and background classes, from 18 in-vivo TTTS fetoscopy procedures and 18 short video clips of an average length of 411 frames for developing placental scene segmentation and frame registration for mosaicking techniques. Seven teams participated in this challenge and their model performance was assessed on an unseen test dataset of 658 pixel-annotated images from 6 fetoscopic procedures and 6 short clips. For the segmentation task, overall baseline performed was the top performing (aggregated mIoU of 0.6763) and was the best on the vessel class (mIoU of 0.5817) while team RREB was the best on the tool (mIoU of 0.6335) and fetus (mIoU of 0.5178) classes. For the registration task, overall the baseline performed better than team SANO with an overall mean 5-frame SSIM of 0.9348. Qualitatively, it was observed that team SANO performed better in planar scenarios, while baseline was better in non-planner scenarios. The detailed analysis showed that no single team outperformed on all 6 test fetoscopic videos. The challenge provided an opportunity to create generalized solutions for fetoscopic scene understanding and mosaicking. In this paper, we present the findings of the FetReg2021 challenge, alongside reporting a detailed literature review for CAI in TTTS fetoscopy. Through this challenge, its analysis and the release of multi-center fetoscopic data, we provide a benchmark for future research in this field.

Skeletal Growth Arrest Lines in Fetal Remains: Histopathology and Correlative Placental Pathology

INTRODUCTION

Skeletal growth arrest lines (GAL) are transverse lines of metaphyseal radiodensity accompanying episodic severe physiological stress. They are poorly described in fetal remains.

MATERIALS AND METHODS

We searched our autopsy practice for instances of fetal GAL in post mortem radiology, and correlated them with long bone histology and placental pathology. We describe the appearance, distribution, and pathology of GAL in a cohort of fetal autopsies, and compare the placental pathology accompanying GAL to the placental pathology of asymmetrical growth restriction (AGR) in the same time period.

RESULTS

In 2108 consecutive fetal post mortems, we found 20 cases with GAL. About 16 were in singletons with AGR. In these 16, the distribution of placental pathologies was similar to a contemporaneous cohort of 113 cases with AGR. Of the remaining 4, two twins out of 9 sets of monochorionic twins with AGR demonstrated GAL. One case of GAL had symmetrical growth restriction with cytomegalovirus infection, and one case had no AGR and an old, unexplained retroplacental hemorrhage. On histology, GAL are characterized by a region of mineralized chondroid, which is variably incorporated into irregular trabecular bone.

DISCUSSION

GALs accompany a variety of placental pathologies and twin-twin transfusion, suggesting episodic disease progression.

Fetal surgery is not associated with increased inflammatory placental pathology

OBJECTIVE

Fetal surgery has improved neonatal outcomes; however, it is unknown if the intervention contributes to the developmental of inflammatory pathologies in the placenta. Here, an association between fetal surgery and placental pathology was examined.

METHOD

This case-control study compared pregnancies with fetal surgery (n = 22), pregnancies with an indication for fetal surgery but without an intervention being done (n = 13), and gestational-age and fetus-number matched controls (n = 36). Data on maternal, infant, and placental outcomes were abstracted. Additionally, immunohistochemistry identified expression of lymphoid and myeloid cells in the placenta on a subset of cases. Comparisons were performed using Kruskal-Wallis or Pearson's chi-squared tests.

RESULTS

Maternal characteristics were comparable between groups. Most fetal interventions were for diaphragmatic hernia, spina bifida, or twin-to-twin transfusion syndrome. Fetuses who were operated on before birth were more likely to be born preterm (p = 0.02). There was no increase in the rate of observed placental pathologies or immune cell infiltration in fetal surgery cases compared to controls.

CONCLUSION

The data suggest that fetal surgery is not associated with increased inflammatory or morphologic pathology in the placenta. This observation supports the growing field of fetal surgery.

Outcome of twin-twin transfusion syndrome according to Quintero stage of disease: systematic review and meta-analysis

OBJECTIVES

To report the outcome of pregnancies complicated by twin-twin transfusion syndrome (TTTS) according to Quintero stage.

METHODS

MEDLINE, EMBASE and CINAHL databases were searched for studies reporting the outcome of pregnancies complicated by TTTS stratified according to Quintero stage (I-V). The primary outcome was fetal survival rate according to Quintero stage. Secondary outcomes were gestational age at birth, preterm birth (PTB) before 34, 32 and 28 weeks' gestation and neonatal morbidity. Outcomes are reported according to the different management options (expectant management, laser therapy or amnioreduction) for pregnancies with Stage-I TTTS. Only cases treated with laser therapy were considered for those with Stages-II-IV TTTS and only cases managed expectantly were considered for those with Stage-V TTTS. Random-effects head-to-head meta-analysis was used to analyze the extracted data.

RESULTS

Twenty-six studies (2699 twin pregnancies) were included. Overall, 610 (22.6%) pregnancies were diagnosed with Quintero stage-I TTTS, 692 (25.6%) were Stage II, 1146 (42.5%) were Stage III, 247 (9.2%) were Stage IV and four (0.1%) were Stage V. Survival of at least one twin occurred in 86.9% (95% CI, 84.0-89.7%) (456/552) of pregnancies with Stage-I, in 85% (95% CI, 79.1-90.1%) (514/590) of those with Stage-II, in 81.5% (95% CI, 76.6-86.0%) (875/1040) of those with Stage-III, in 82.8% (95% CI, 73.6-90.4%) (172/205) of those with Stage-IV and in 54.6% (95% CI, 24.8-82.6%) (5/9) of those with Stage-V TTTS. The rate of a pregnancy with no survivor was 11.8% (95% CI, 8.4-15.8%) (69/564) in those with Stage-I, 15.0% (95% CI, 9.9-20.9%) (76/590) in those with Stage-II, 18.6% (95% CI, 14.2-23.4%) (165/1040) in those with Stage-III, 17.2% (95% CI, 9.6-26.4%) (33/205) in those with Stage-IV and in 45.4% (95% CI, 17.4-75.2%) (4/9) in those with Stage-V TTTS. Gestational age at birth was similar in pregnancies with Stages-I-III TTTS, and gradually decreased in those with Stages-IV and -V TTTS. Overall, the incidence of PTB and neonatal morbidity increased as the severity of TTTS increased, but data on these two outcomes were limited by the small sample size of the included studies. When stratifying the analysis of pregnancies with Stage-I TTTS according to the type of intervention, the rate of fetal survival of at least one twin was 84.9% (95% CI, 70.4-95.1%) (94/112) in cases managed expectantly, 86.7% (95% CI, 82.6-90.4%) (249/285) in those undergoing laser therapy and 92.2% (95% CI, 84.2-97.6%) (56/60) in those after amnioreduction, while the rate of double survival was 67.9% (95% CI, 57.0-77.9%) (73/108), 69.7% (95% CI, 61.6-77.1%) (203/285) and 80.8% (95% CI, 62.0-94.2%) (49/60), respectively.

CONCLUSIONS

Overall survival in monochorionic diamniotic pregnancies affected by TTTS is higher for earlier Quintero stages (I and II), but fetal survival rates are moderately high even in those with Stage-III or -IV TTTS when treated with laser therapy. Gestational age at birth was similar in pregnancies with Stages-I-III TTTS, and gradually decreased in those with Stages-IV and -V TTTS treated with laser and expectant management, respectively. In pregnancies affected by Stage-I TTTS, amnioreduction was associated with slightly higher survival compared with laser therapy and expectant management, although these findings may be confirmed only by future head-to-head randomized trials. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Cardiac Anomalies in Liveborn and Stillborn Monochorionic Twins

BACKGROUND

Cardiovascular anomalies are more common in monochorionic twins, especially with twin-twin transfusion, compared to other twin types and to singletons. Because previous studies are based on fetal and neonatal echocardiography, more information is needed to study prevalence of cardiac anomalies in twin miscarriages, stillbirths, and children after the immediate neonatal period.

METHODS

With specific attention to cardiac anomalies, we reviewed the medical records of 335 selected liveborn twin pairs from the Marshfield Clinic Twin Cohort (enriched for twin-twin transfusion) and all twins (175 pairs) identified in the Wisconsin Stillbirth Service Program cohort of late miscarriages and stillbirths.

RESULTS

Structural cardiac defects occurred in 12% of liveborn monochorionic twin infants and 7.5% of stillborn infants with twin-twin transfusion compared to only 2% of liveborn dizygotic twins and no stillborn dizygotic infants. The most common cardiac lesion in liveborn twins was ventricular septal defect, which was usually isolated and discordant, preferentially affecting the smaller twin in monochorionic pairs. Among stillborn and miscarried monochorionic twins, the most common cardiac lesion was acardia.

CONCLUSIONS

Monochorionic twins, particularly those with TTT, are at increased risk for a spectrum of structural cardiac malformations which we suggest may be related to asymmetry of the inner cell mass resulting in a smaller poorly perfused twin. In severe cases, limited cardiac and circulatory development in the affected twin leads to acardia. In less severe cases, the smaller infant has deficient septal growth that sometimes results in ventricular septal defect.

Significance of placental cord insertion site in twin pregnancy

OBJECTIVE

To investigate the association between abnormal cord insertion and the development of twin-specific complications, including birth-weight discordance, selective fetal growth restriction (sFGR) and twin-to-twin transfusion syndrome (TTTS).

METHODS

This was a single center retrospective cohort study of twin pregnancies. Abnormal cord insertion was defined as either marginal (umbilical cord attachment site less than 2 cm to the nearest margin of the placental disc) or velamentous (cord attached to the membrane before reaching the placental disc with clear evidence of vessels traversing the membranes to connect with the placental disc), as described in placental pathology reports. Twins with major structural or chromosomal abnormalities and monochorionic monoamniotic twins were not included in the study. Information on the pregnancies, ultrasound findings, prenatal investigations and interventions was obtained from the electronic ultrasound database, while data on placental histopathological findings, pregnancy outcome, mode of delivery, birth weight, gestational age at delivery and admission to the neonatal intensive care unit were obtained from maternity records. Categorical variables were compared using the chi-square or Fisher's exact test, while continuous variables were compared using the Student's t-test, ANOVA for multiple comparisons and the Kruskal-Wallis test.

RESULTS

Of the 497 twin pregnancies included in the analysis, 351 (70.6%) were dichorionic and 146 (29.4%) were monochorionic. The incidence of birth-weight discordance of 25% or more was significantly higher in pregnancies with velamentous and those with marginal cord insertions compared to those with normal cord insertion (24.0%, 15.3% vs 7.6%, P < 0.001 and P = 0.020, respectively). In pregnancies with birth-weight discordance of 25% or more, the smaller twins had significantly higher prevalence of velamentous (13.8%) and marginal (34.2%) cord insertions compared with the larger twins (1.8% and 18.5%, respectively, P < 0.001). The smaller twins of the monochorionic diamniotic pregnancies showed an even higher prevalence of velamentous (29.5%) and marginal (40.9%) cord insertions compared with the larger twins (2.3% and 31.5%, respectively, P < 0.001). Compared with the normal cord insertion group, only velamentous insertion was associated significantly with the risk of sFGR (odds ratio (OR), 9.24 (95% CI, 2.05-58.84), P < 0.001) and birth-weight discordance of 20% or more (OR, 4.34 (95% CI, 1.36-14.61), P = 0.007) and 25% or more (OR, 6.81 (95% CI, 1.67-34.12), P = 0.003) in monochorionic twin pregnancies. There was no significant association between velamentous cord insertion and TTTS (P = 0.591), or between marginal cord insertion and the development of sFGR (P = 0.233), birth-weight discordance of 25% or more (P = 0.114) or TTTS (P = 0.487). Subgroup analysis of dichorionic twins showed that abnormal cord insertion was not associated with the risk of birth-weight discordance (P = 0.999), sFGR (P = 0.308), composite neonatal adverse outcome (P = 0.637) or intrauterine death (P = 0.349).

CONCLUSION

Monochorionic twins with velamentous cord insertion are at increased risk of birth-weight discordance and sFGR. Sonographic delineation of placental cord insertion could be of value in the antenatal stratification of twin pregnancies. Prospective studies are required to assess the value and predictive accuracy of this potential screening marker. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

[Rare forms of feto-fetal transfusion in a clinical practice]

OBJECTIVE

To analyze monochorionic twin pregnancies with twin anemia polycythemia sequence (TAPS) and acute peripartal twin to twin syndrome (aTTTS), to compare their prenatal management and perinatal outcome.

METHODS

Retrospective analysis of monochorionic biamniotic twin pregnancies without signs of chronic TTTS within a period 10/2010 to 10/2013. Further selection of cases with haemoglobin difference in neonates greater than 50 g/l was made, type of feto-fetal haemorrhage was determined and their prenatal and postnatal characteristics were described.

RESULTS

Based on the criteria described above we selected four cases out of 55 monochorionic pregnancies. One case of prenatally diagnosed spontaneous TAPS which fulfilled all the diagnostic criteria with typical angioarchitecture inclusive, one case of spontaneous TAPS diagnosed postnatally, a case of postlaser TAPS with a spontaneous resolution and one unusual case of feto-fetal haemorrhage which does not fully meet criteria of TAPS or aTTTS. All the pregnancies were delivered by caesarean section. All the anaemic neonates required blood transfusion postpartum and two of the polycythemic neonates needed partial exsanguination.

CONCLUSION

Rare forms of feto-fetal transfusion syndrome form a heterogenous group and it may be difficult to distinguish between TAPS and aTTTS in certain cases. A recommendation for a management of TAPS cases was published in recent literature. However, correct interpretation of dopplerometric measurments belongs to the hands of experienced ultrasonographers in perinatal centers.

[TWIN-TO-TWIN TRANSFUSION SYNDROME: THE POSSIBILITY OF LATENT FLOW (CASE REPORT)]

The early diagnosis of the Twin-To-Twin transfusion syndrome (TTTS) carries benefits of the better survivor for the fetus-donor; but at the same time there are obvious practical impediments to diagnose the condition earlier in the course of a pregnancy. That's why this particular problem in practical medicine requires in depth investigation to clarify casual factors, and specify tactical approach to the prospective patients which in turn will lead to prevention of the fetal death and damage and improvement of fetal survivor in any form of TTTS. The TTTS is one of the complications of a monochorionic pregnancy leading to fetal distress and certain developmental abnormalities as well as worse prognosis for the survival for the affected twin. Previous scientific researches established two major forms of TTTS: chronic - which develops over period of time during the course of the pregnancy and acute - which can develop during the labor itself. This scientific article represents description and analysis of the clinical case of the monozygotic (identical) twin pregnancy characterized by antenatal asphyxia of one of the fetuses at the full-term with unclear clinical etiology but with all morphological characteristics specific for TTTS for monochorionic diamniotic pregnancy. Analyzing the data from this clinical case we have decided that there are latent forms of TTTS which can manifest in the third trimester of the pregnancy.

The TRAP (twin reversed arterial perfusion) sequence - case presentation

We present a particular case of TRAP (twin reversed arterial perfusion) syndrome, which has a very rarely association of the simultaneous existence of a rudimentary malformed heart and brain, and also other malformations like abdominal wall abnormality, absent bladder with present kidneys, and absence of the lungs, which appear only in a few cases on the receptor twin from this sequence, malformations incompatible with life. A Caucasian 26-year-old pregnant woman, at the first pregnancy, with a monochorionic-diamniotic pregnancy, 26 weeks of gestation was referred to our hospital, for polyhydramnios. The patient delivered a living female newborn, weighing 950 g, with an Apgar score of 2 at one minute - the donor fetus and a second female newborn with multiple malformations, no signs of life and who weighed 2300 g - the receptor fetus. The anatomopathological examination confirmed the TRAP sequence associated with severe facial dysmorphism, bilateral phocomelia and cardiac malformations (rudimentary hypoplastic, univentricular) and a vascular anastomosis between the two umbilical cords. Anemia and cardiac complications which can lead to cardiac failure, appear early during pregnancy and caused the death of the pumping twin. We emphasize that in our case of TRAP sequence, the ultrasound examination established the diagnosis of the syndrome with high accuracy. Therefore, we can conclude that the existence of a rudimentary heart and a vascular anastomosis between the two umbilical cords supports the apparition of TRAP sequence. The early diagnosis of this pathology, the observation of the pregnancy with the help of weekly ultrasounds and the intrauterine interventions can increase the survival chances of the donor fetus from the TRAP sequence.

Postnatal MRI Brain in Infants Treated for Twin-Twin Transfusion Syndrome

Untreated twin-twin transfusion syndrome (TTTS) is associated with significant mortality and neurological impairment. Fetoscopic laser surgery (FLS) is the treatment of choice. We sought to assess intracranial abnormalities in TTTS twins following treatment. In this prospective, blinded study MRI scans were performed on 3 groups; (1) monochorionic diamniotic (MCDA) twins with TTTS who had undergone FLS (n = 10), (2) MCDA twins without TTTS (n = 8) and (3) dichorionic twins (n = 8). Scans were scored as either normal or abnormal. The primary outcome was a composite of abnormal MRI brain or intrauterine fetal demise. The primary outcome occurred in 6/10 (60%) of the TTTS group versus 3/8 (37.5%) in the MCDA group. The primary outcome was significantly different across all study groups [p = 0.029; X2 = 7.112]. We found that twins treated for TTTS are more likely to have abnormalities on MRI brain at term than other twin groups. This group merits term-corrected MRI as part of their postnatal assessment.

Single fetal demise in monochorionic pregnancies: incidence and patterns of cerebral injury

OBJECTIVE

To evaluate the incidence, type and severity of cerebral injury in the surviving monochorionic (MC) cotwin after single fetal demise in twin pregnancies.

METHODS

All MC pregnancies with single fetal demise that were evaluated at the Leiden University Medical Center between 2002 and 2013 were included. Perinatal characteristics, neonatal outcome and the presence of cerebral injury, observed on neuroimaging, were recorded for all cotwin survivors.

RESULTS

A total of 49 MC pregnancies with single fetal demise, including one MC triplet, were included in the study (n = 50 cotwins). Median gestational age at occurrence of single fetal demise was 25 weeks and median interval between single fetal demise and live birth was 61 days, with a median gestational age at birth of 36 weeks. Severe cerebral injury was diagnosed in 13 (26%) of the 50 cotwins and was detected antenatally in 4/50 (8%) and postnatally in 9/50 (18%) cases. Cerebral injury was mostly due to hypoxic-ischemic injury resulting in cystic periventricular leukomalacia, middle cerebral artery infarction or injury to basal ganglia, thalamus and/or cortex. Risk factors associated with severe cerebral injury were advanced gestational age at the occurrence of single fetal demise (odds ratio (OR), 1.14 (95% CI, 1.01-1.29) for each week of gestation; P = 0.03), twin-twin transfusion syndrome developing prior to single fetal demise (OR, 5.0 (95% CI, 1.30-19.13); P = 0.02) and a lower gestational age at birth (OR, 0.83 (95% CI, 0.69-0.99) for each week of gestation; P = 0.04).

CONCLUSIONS

Single fetal demise in MC pregnancies is associated with severe cerebral injury occurring in 1 in 4 surviving cotwins. Routine antenatal and postnatal neuroimaging, followed by standardized long-term follow-up, is mandatory.

[Clinical effect of fetoscopic laser occlusion of chorioangiopagous vessels for twin-twin transfusion syndrome: experience of an center from China]

OBJECTIVE

To study the clinical effect of fetoscopic laser occlusion of chorioangiopagous vessels (FLOC) in treating twin to twin transfusion syndrome.

METHODS

The clinical data of 44 consecutive cases of twin to twin transfusion syndrome (TTTS)who had FLOC in the Department of Obstetrics and Gynaecology of Peking University Third Hospital were reviewed and analyzed for perioperative complications, perinatal outcomes and fetal survival rate.

RESULTS

(1) PATIENT CHARACTERISTICS: the mean maternal age was (29±4) years, the median gestational age at TTTS being primarily diagnosed was 20.4 weeks, the median gestational age at FLOC was 21.2 weeks. According to the Quintero staging system, there were 9 cases had stages progressed before the operation. (2) FLOC parameter and intraoperative complications: 44 cases all could tolerate the operation; there was 1 case of placenta vascular rupture in the operation, no fetal body injury by laser or placental abruption. 3 cases underwent cervical cerclage following FLOC. The average operation time of 41 cases alone with FLOC was (60.1±15.1) minutes. (3) Postoperative complications: the rate of intrauterine fetal death was 15% (13/88), the rate of intrauterine growth restriction after FLOC was 5% (4/88), the rate of membranes rupture less than 28 weeks was 16% (7/44), the rate of TAPS after FLOC was 5% (2/44), the rate of membrane sepration after FLOC was 5% (2/44). (4) Perinatal outcome and survival rate: there were 25 patients after FLOC had delivered in the perinatal period. The average gestational age of delivery was (33.5±2.7) weeks. The donor fetuses survival rate was 88% (22/25), the recipient fetuses survival rate was 100% (25/25). The birth weight of donor fetuses was significantly less than that of recipient fetuses (1 631g vs 2 071 g, P = 0.016). From Quintero staging I to IV, the rate that 44 cases of TTTS had entered the perinatal period was 4/7, 11/14, 7/19, 3/4; both twins survival rates were 4/7, 10/14, 5/19, 3/4; all the fetal survival rate was 8/14, 75% (21/28), 32% (12/38), 6/8, respectively. (5) Compared the early stage (I+II) with the advanced stage (III+IV), the rates that 44 cases of TTTS had entered the perinatal period (71% vs 44%) and that both twins survived (67% vs 35%) had no statistically significance. The rate that all the fetus survived in the early stage was significantly (69% vs 39%) more than that in the advanced stage. (6) All the cases of neoborn were followed up till 1 month postpartum, the donor fetuses and the recipient fetuses had 12 and 5 cases of cardiac abnormalities respectively, each had 1 case of neonatal death and 2 cases of neonatal white matter damage.

CONCLUSIONS

FLOC for TTTS is associated with a better survival rate. Quintero staging probably does not effectively predict the fetal diagnosis of TTTS after FLOC. When TTTS diagnosed, the sooner FLOC given, the better fetal prognosis had.

Indirect pump: unique presentation of a monochorionic-triamniotic triplet gestation complicated by TRAP sequence and successfully managed with radiofrequency ablation of the acardiac fetus

Twin reversed arterial perfusion (TRAP) sequence is a rare complication of multiple gestations. Only a few cases of TRAP sequence in monochorionic triplets have been reported. Here we report a case of TRAP sequence in a monochorionic-triamniotic triplet gestation treated with radiofrequency ablation of the acardiac fetus. The response to the radiofrequency ablation procedure and subsequent examination of the placenta support the hypothesis of an 'indirect' pump triplet.

First successful case of non-invasive in-utero treatment of twin reversed arterial perfusion sequence by high-intensity focused ultrasound

High-intensity focused ultrasound (HIFU) has excellent potential as a non-invasive therapeutic tool in various fields of medicine. We present a case of twin reversed arterial perfusion sequence, in which non-invasive blood flow occlusion in the acardiac fetus was successfully achieved by means of HIFU exposure from outside the maternal abdomen. HIFU was applied to blood vessels of the acardiac fetus at the point at which the umbilical cord entered the body in a series of four procedures at 3-day intervals starting at 13 weeks' gestation, and in a final procedure with higher power at 17 weeks. The HIFU intensity was set at approximately 2300 W/cm(2) for the initial series of procedures and at 4600 W/cm(2) for the final procedure, with exposure periods of 10 s. As color Doppler examination revealed absence of blood flow to the acardiac fetus after the second round of HIFU exposure, we concluded that complete occlusion of target vessels had been achieved. Delivery was by Cesarean section at 37 weeks' gestation. A male neonate (the pump fetus) was born weighing 1903 g with Apgar scores of 8 and 9 at 1 and 5 min, respectively. At the time of writing, the baby was healthy and growing normally, with the exception of congenital pseudarthrosis.

[Research of placental vascular distribution and clinical outcome in monochorionic twins]

OBJECTIVE

To study the placental vascular distribution of monochorionic (MC) twins with twin-to-twin transfusion syndrome (TTTS) or birth weight discordance.

METHODS

Twenty-eight MC placentas were injected in Peking University Third Hospital between Feb. 2010 and Feb. 2011. The vascular distribution type (parallel, crossed, mixed and monoamniotic), the anastomosis of vessels and the placental sharing were recorded. The outcome of pregnancy and the placental characteristics of birth weight discordance (birth weight discordance≥20%) in non-TTTS MC twins were analyzed.

RESULTS

(1) The outcome of pregnancy: the miscarriage or gestational weeks of 28 MC twins were 20 to 38 weeks (median of 35 weeks). Six cases were TTTS, 3 of which received fetoscopic laser occlusion of communicating vessels (FLOC). There were 48 live births, with an average birth weight of (2036±623) g. (2) Type of placental vascular distribution:in the 28 MC placentas, number of parallel, crossed, mixed and monoamniotic type of placental vascular distribution were 4 (14%), 14 (50%), 6 (21%) and 4 (14%) cases, respectively. No parallel type was found in TTTS. There was no significant difference of vascular anastomosis or unequal placental sharing among the different placental vascular distribution types (P>0.05). (3) Characteristics of placental vascular distribution in birth weight discordance twins:there were 20 non-TTTS MC twin pregnancies, all of which got live births of both babies. Birth weight discordance equal to or more than 20% was found in 6 pairs of newborns, while birth weight discordance less than 20% was found in the rest 14 cases. Ratio of unequal placental sharing was significantly different between the two groups (P<0.01). There was no significant difference of umbilical cord insertion, placental vascular distribution and anastomosis in the two groups (P>0.01).

CONCLUSIONS

Vascular distribution type of MC twins might be related to TTTS. Unequal placental sharing is a risk factor of birth weight discordance in non-TTTS MC twins.

Twin reversed arterial perfusion sequence in a triplet natural pregnancy:case report from Korle Bu Teaching Hospital, Accra, Ghana and a review of the literature

BACKGROUND

Twin reversed arterial perfusion sequence is probably the most severe malformation found in humans.It is also called acardia ,acardiac twinning or acardius acephalus and is a very rare condition that occurs in monozygotic twins and rarely in triplet pregnancy. It has not been described in the West African Medical literature. A case was recorded in a twin delivery at the labour ward four years ago in the same hospital but the underlying diagnosis was not made.

OBJECTIVE

To describe a rare case of twin reversed arterial perfusion sequence occurring in a triplet pregnancy and review the current literature.

METHODS

A case was evaluated at the delivery ward,Department of Obstetrics and the Neonatal unit of the Korle Bu Teaching Hospital upon information from the obstetric team that a monster had been born from a triplet set. Full documentation was done.

RESULTS

The case documented was a twin reversed arterial perfusion sequence in a triplet pregnancy.

CONCLUSION

This rare condition has been well characterized and Obstetricians and Paediatricians should now be able to make an accurate diagnosis.

High-intensity focused ultrasound treatment for twin reversed arterial perfusion sequence

Twin reversed arterial perfusion (TRAP) sequence is a serious complication of monochorionic twin pregnancies, in which arterioarterial anastomoses allow blood flow from a 'pump' fetus to an acardiac fetus via reversed flow in the latter's umbilical artery. Several trial treatments for TRAP sequence have been reported, but all of these have been invasive. We present a case of TRAP sequence in which high-intensity focused ultrasound (HIFU) was applied to the umbilical artery of the anomalous twin at 26 weeks as a non-invasive fetal therapy. The HIFU intensity was set at approximately 2300 W/cm(2) with exposure periods of 10 s. Color Doppler ultrasound showed a decrease in blood supply to the anomalous twin, although complete occlusion of the targeted vessel was not achieved. Delivery was by Cesarean section at 29 weeks' gestation and the pump twin survived, without severe clinical complications at 6 months.

[Fetoscopic guided laser occlusion for twin-to-twin transfusion syndrome in 33 cases]

OBJECTIVE

To evaluate the clinical effect of fetoscopic laser occlusion of chorioangiopagous vessels (FLOC) for monochorionic diamniotic twins (MCDA) pregnancies complicated with twin-to-twin transfusion syndrome(TTTS).

METHODS

The clinical data of 33 consecutive cases of TTTS from Mainland China, who had FLOC in the Department of Obstetrics and Gynaecology of Prince of Wales Hospital (The Chinese University of Hong Kong) from November 2003 to December 2010, were reviewed and analyzed for peri-operative complications, perinatal outcomes and fetal survival rate. Clinical stage of TTTS was according to the Quintero staging system.

RESULTS

(1) Pregnancy characteristics: the mean maternal age was 30; the median gestational age at FLOC was 23(+4) weeks; according to the Quintero staging system, 3 cases were Quintero staging I, 14 cases were Quintero staging II, 7 cases were Quintero staging III and 9 cases were Quintero staging IV. For the 3 stage I cases, FLOC was performed for severe maternal symptoms of polyhyramnios or severe fetal cardiac dysfunction. (2) COMPLICATIONS: intraoperative complications occurred in 5 patients including four uterine bleedings at the puncture site, one placental vascular anastomosis bleeding. Postoperative complications occurred in 6 patients including 2 abortions and 1 intrauterine death within one week after operation, 2 abortions and 1 amniotic band syndrome occurred from two to four weeks after operation. (3) Perinatal outcome and fetal survival rate: the median interval of 33 patients between FLOC and delivery was 9(+4) weeks; the median gestational age at delivery was 31(+6) weeks; the gestation at delivery was less than 24 weeks in 6% (2/33), 24 to 28 weeks in 21% (7/33), 28 to 32 weeks in 18% (6/33), 32 to 37 weeks in 55% (18/33). The mean birth weight of the donor was 1600 g (350 - 2520 g); the mean birth weight of the recipiert was 1930 g (400 - 3040 g). The overall survival rate, the double infant survival rate, the single survival rate and survival rate for at least one twin was 59% (39/66), 52% (17/33), 15% (5/33) and 67% (22/33), respectively. The overall survival rate dropped from 61% (17/28) in Quintero staging II to 9/18 in Quintero staging IV.

CONCLUSIONS

FLOC for MCDA complicated with TTTS is associated with an overall survival of about 60%. Major complications are rare. The outcome is not only related to Quintero staging but also the close monitoring and timely termination of pregnancy.

[Are in-utero interventions justified? Perspective of neonatologists. Part III. Twin to Twin Transfusion Syndrome and Congenital Heart Defects]

INTRODUCTION

TTTS complicates from 10 to 15% of monochorionic diamniotic pregnancies. Expectant management is associated with 80 - 100% mortality First in-utero intervention in the fetus with CHD was performed in 1991. However only recently have they attained wider acceptance of cardiologists and perinatologists.

OBJECTIVE

Our main objective was to analyze the studies evaluating prenatal interventions in pregnancies complicated by TTTS or CHD, and to determine whether given the available data, those interventions are justified.

METHODS

Pubmed and Cochrane database were searched for all studies related to in-utero interventions in fetuses with TTTS or CHD. Emphasis was placed on randomized controlled trials.

RESULTS

Meta-analysis published in Cochrane database concludes that laser photocoagulation of communicating vessels improves outcome in all stages of TTTS. Additional studies are required to elucidate the role of amnioreduction. For interventions in fetuses with CHD published data is limited to the case series. Potentially selected patients with CHD would benefit from in-utero intervention, but additional studies are required.

CONCLUSIONS

Prenatal interventions in TTTS improve the outcome. Further studies are required to define their role in patients with CHD. For all procedures selection criteria and indications for interventions need to be clarified. More precise prenatal diagnosis and improvements in the area of fetal monitoring during the procedure might positively impact survival Preterm birth and premature rapture of membranes remain significant adverse outcomes. Complications associated with prematurity might counteract the positive effect of fetal intervention. Most cases of in-utero interventions should only be performed in specialized centers as a part of a clinical trial protocol.

Outcomes in a cohort of patients with Stage I twin-to-twin transfusion syndrome

OBJECTIVE

To determine pregnancy outcomes of patients who present with Stage I twin-to-twin transfusion syndrome (TTTS).

METHODS

This was a retrospective review of all patients with TTTS referred to our institution between January 2005 and December 2006. Quintero criteria were used for staging. Laser ablation was not offered to patients with Stage I disease.

RESULTS

A total of 155 twin pregnancies were evaluated for TTTS during this period. Forty-two met the criteria for Stage I and were included in the analysis. The overall survival to discharge was 82%. The mean gestational age at the time of consultation was 20.9 +/- 0.4 weeks. A total of 23 cases (54.8%) underwent amnioreduction. Progression of TTTS requiring invasive therapy occurred in four cases. The mean gestational age at delivery was 32.5 +/- 0.62 weeks. When divided according to use of amnioreduction, there were no statistically significant differences between the groups for gestational age at delivery or for birth weight. Those Stage I cases with a CHOP cardiovascular score of 5 or higher delivered almost 3 weeks earlier than the remainder of the cohort.

CONCLUSIONS

Progression of TTTS beyond Stage I occurred in only 9.5% of the cohort. Mean gestational age at delivery and survival to discharge did not differ between Stage I patients and those treated with placental laser ablation for more advanced stages of TTTS.

[Analysis of the perinatal outcomes and management of twin-twin transfusion syndrome]

OBJECTIVE

To investigate the perinatal outcomes of twin-twin transfusion syndrome (TTTS) and the management.

METHODS

During Nov 1, 2002 to Sep 30, 2005, 24 cases of TTTS in Beijing Obstetrics and Gynecology Hospital were analyzed. The outcomes of them were compared with the pregnancy without TTTS in all twins and in monozygotic twins. The outcomes of the blood-supplying fetus and the blood-recepter were compared.

RESULTS

6.8% cases had TTTS in all twins. The group of TTTS had more maternal, fetal and neonatal complications than twins pregnancy without TTTS: polyhydramnios [37.5% (9/24) vs 2.1% (7/328), P < 0.01], gestational hypertension [20.8% (5/24) vs 7.0% (23/328), P = 0.043], premature labor [66.7% (16/24) vs 36.3% (119/328), P = 0.003], perinatal dead fetus in uterus [18.8% (6/32) vs 1.1% (7/640), P < 0.01], neonatal asphyxia [73.1% (19/26) vs 3.0% (19/632), P < 0.01], the proportion of NICU [88.5% (23/26) vs 23.4% (148/632), P < 0.01], neonatal death [15.4% (4/26) vs 1.7% (11/632), P = 0.002] and the rate of perinatal mortality [31.2% (0/32) vs 2.8% (18/632)]. Compared with the monozygotic twins without TTTS, in TTTS group there were more complications of the mother, the fetus and the neonates: gestational hypertension [20.8% (5/24) vs 9.9% (14/142), P = 0.224], premature labor [66.7% (16/24) vs 49.3% (70/142), P = 0.115], perinatal dead fetus in uterus [18.8% (6/32) vs 0.7% (2/282), P < 0.01], neonatal asphyxia [73.1% (19/26) vs 3.9% (11/280), P < 0.01], the proportion of NICU [88.5% (23/26) vs 29.3% (82/280), P < 0.01], neonatal death [15.4% (4/26) vs 2.1% (6/280), P = 0.006] and the rate of perinatal mortality [31.3% (10/32) vs 3.2% (8/282)]. The perinatal outcomes were better in those cases that the grades of TTTS were below 3 in the first diagnosis.

CONCLUSIONS

We should try to diagnose and treat TTTS as early as possible because the outcome is poor.

The effect of fetoscopic laser therapy on fetal cardiac size in twin-twin transfusion syndrome

OBJECTIVES

To evaluate the influence of fetoscopic laser therapy on fetal cardiac size in monochorionic twins complicated by twin-twin transfusion syndrome (TTTS).

METHODS

In a longitudinal, prospective study, we assessed fetal cardiac size sonographically in monochorionic diamniotic twins with TTTS treated by laser therapy and in monochorionic twins without TTTS. The fetal cardiothoracic ratio (cardiac circumference divided by thoracic circumference) of TTTS twins was determined within 24 h before, 12-24 h after and 1 week after laser treatment, and from then on every 2-4 weeks until birth. TTTS twins were classified into Quintero Stages 1-2 (n = 18) and Stages 3-4 (n = 16), and measurements were compared with biweekly measurements of non-TTTS monochorionic twins matched for gestational age (n = 38). Cardiomegaly was defined as a cardiothoracic ratio above the 97.5th percentile.

RESULTS

Before laser treatment, cardiomegaly was observed in 44% (8/18) and 50% (8/16) of recipients in Quintero Stages 1-2 and Stages 3-4, respectively. Cardiomegaly occurred in none of the donors before treatment. After laser treatment, cardiomegaly was observed in 76% (13/17) and 50% (7/14) of recipients in Stages 1-2 and Stages 3-4, respectively, and in 17% (3/18) and 13% (2/15) of donors in Stages 1-2 and Stages 3-4, respectively. Cardiomegaly was present in 18% (7/38) and 8% (2/25) of non-TTTS monochorionic twins and singletons. After laser therapy, the cardiothoracic ratio of recipients in Stages 1-2 and Stages 3-4 was not significantly changed (P = 0.34 and P = 0.67, respectively). The cardiothoracic ratio of donors in Stages 1-2 and Stages 3-4 was increased compared with that before laser therapy (P = 0.0002 and P = 0.005, respectively). Cardiothoracic ratios of non-TTTS monochorionic twins were not significantly different from our reference range in singletons throughout gestation, and were smaller than those in both recipients and donors after laser therapy.

CONCLUSIONS

TTTS recipients show cardiomegaly before as well as after fetoscopic laser therapy for TTTS. Donors develop cardiomegaly only after laser treatment. Our findings emphasize the significant effect of TTTS and fetoscopic laser therapy on the fetal heart of both recipient and donor twins.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Segmental arterial mediolysis with accompanying venous angiopathy: a clinical pathologic review, report of 3 new cases, and comments on the role of endothelin-1 in its pathogenesis

The authors review 20 cases of segmental arterial mediolysis (SAM) including 3 newly reported cases. SAM developed in areas of vascular distention in 2 of the latter cases: 1 in utero in the heart of a recipient of a twin transfusion syndrome and the other in the jejunum secondary to partial venous obstruction. In the third case, it occurred in a patient with Raynaud disease. Characterizing SAM are injurious and reparative lesions that occur in the media and/or at the adventitial medial junction. Four distinctive alterations are recognized: (1) mediolysis, (2) a tearing separation of the outer media from adventitia, (3) arterial gaps, and (4) a florid reparative response that replaces zones of mediolysis and fills areas of medial adventitial separation. The repair can transform SAM into lesions indistinguishable from common types of fibromuscular dysplasia (FMD.) A venous angiopathy involving large and medium-sized veins accompanies SAM. It features medial muscle vacuolar change with lysis leading to apparent separation of residual muscle bundles. Immunostaining shows endothelin-1 (ET-1) decorating adventitial capillaries in SAM and neighboring arteries, in capillaries of adjoining tissues, and outlining smooth muscle cell membranes in adjacent veins including those of the venous angiopathy. The significance of these changes is uncertain. Vasospasm is believed to cause SAM, but ET-1 is not the direct pressor agent responsible for this condition. The reason(s) for synthesis and release of ET-1 in SAM are still hypothetical, but local perturbations in vascular tone may be an important factor. ET-1 may be indirectly play a role in SAM by cross-talking and potentiating the activities of other vasoconstrictors such as norepinephrine and by orchestrating its reparative phase.

Discordance in nuchal translucency thickness in the prediction of severe twin-to-twin transfusion syndrome

OBJECTIVE

To examine in monochorionic pregnancies the possible value of intertwin discordance in nuchal translucency (NT) thickness in the prediction of early fetal death or severe twin-twin transfusion syndrome (TTTS).

METHODS

In 512 monochorionic twin pregnancies NT was measured at 11 to 13 + 6 weeks' gestation and regression analysis was used to determine the significance of the association between the intertwin discordance in NT and subsequent early fetal death or development of severe TTTS requiring endoscopic laser surgery.

RESULTS

In 412 (80.5%) pregnancies there was a normal outcome, in 58 (11.3%) there was severe TTTS requiring endoscopic laser surgery at 18-24 weeks, in 19 (3.7%) there was death of one or both fetuses at 13-18 weeks and in 23 (4.5%) there was fetal death at 21-38 weeks. In the four outcome groups the median discordance in NT was 11%, 22%, 35% and 7%, respectively. Significant prediction of early fetal death and severe TTTS was provided by the discordance in fetal NT, which was not significantly improved by including the discordance in crown-rump length. If the discordance in NT was 20% or more, the false positive rate was 20%, the detection rate of early fetal death was 63% and the detection rate of severe TTTS was 52%.

CONCLUSIONS

Discordance in NT of 20% or more is found in about 25% of monochorionic twins and in this group the risk of early fetal death or development of severe TTTS is more than 30%. If the discordance is less than 20% the risk of complications is less than 10%.

TRAP sequence in an acardiac twin

CASE REPORT

The authors present a case of an acardiac twin gestation diagnosed sonographically at 20 weeks with evidence of twin reversed-arterial perfusion (TRAP) sequence. The acardius appeared to be less than half the estimated weight of the pump twin. The acardius was identified as an amorphous mass, without extremities. The parents chose expectant management rather than surgical intervention. Observation by serial sonographic and color Doppler evaluation was performed. At 34 weeks, a healthy infant was delivered by cesarean section after showing signs of fetal congestive heart failure (CHF). The acardius was 2/3 the size of the infant at delivery.

CONCLUSION

Expectant management with close antepartum surveillance deserves consideration in cases of monozygotic twins with TRAP sequence. Neonatal mortality of the pump twin diagnosed antenatally may be considerably less than reported.

Multiple thromboembolic events in fetofetal transfusion syndrome in triplets contributing to the understanding of pathogenesis of hydranencephaly in combination with polymicrogyria

Over the last 180 years, several theories concerning the origin of hydranencephaly have been proposed with an emphasis on infectious, aplastic, and vascular etiologies. In this report, we present a case of triplets with fetofetal transfusion syndrome of which 2 fetuses (1 and 2) developed almost similar hydranencephaly, whereas the third exhibited the features of a fetus papyraceus (3). In the monochorial triamniotic placenta, multiple arteriovenous anastomoses were detected, representing a probable route for the transmission of thrombi originating from fetus 3 causing visceral lesions in fetus 2. Hydranencephaly was histologically characterized by necrosis, macrophage invasion, and endothelial proliferation. In addition, polymicrogyria was seen in fetuses 1 and 2. The combination of multiple visceral thromboembolic events and the death of fetus 3 approximately in the 11th week of gestation suggested a vascular thrombotic pathogenesis of hydranencephaly. Polymicrogyria can be considered as postmigratory laminar necrosis. Our findings contribute to the pathogenetic understanding of combined hydranencephaly and polymicrogyria.

Stage-Related Outcome in Twin–Twin Transfusion Syndrome Treated by Fetoscopic Laser Coagulation

OBJECTIVE

To assess perinatal outcome in monochorionic twin pregnancies according to different stages of severe mid-trimester twin-twin transfusion syndrome managed by fetoscopic laser coagulation of the placental vascular anastomoses.

METHODS

In a prospective study fetoscopic laser therapy was performed in 200 consecutive pregnancies with severe mid-trimester twin-twin transfusion syndrome at a median gestational age of 20.7 weeks (range 15.9-25.3 weeks). Outcome data were analyzed for the whole group and separately for each stage according to the Quintero staging system.

RESULTS

The overall survival rate was 71.5% (286/400), with survival of both twins in 59.5% (119/200) and survival of at least one of the twins in 83.5% (167/200). The median gestational age at delivery of liveborn neonates was 34.3 weeks (range 23.1-40.4 weeks). There was a significant trend toward reduced survival rates with increasing stage (P=.038). The percentage of pregnancies with survival of both fetuses was 75.9% (22/29) for stage I, 60.5% (49/81) for stage II, 53.8% (43/80) for stage III, and 50% (5/10) for stage IV. At least one of the twins survived in 93.1% (27/29) at stage I, 82.7% (67/81) at stage II, 82.5% (66/80) at stage III, and 70% (7/10) at stage IV. The overall survival rate for donor fetuses was 70.5% (141/200) and for recipient fetuses, 72.5% (145/200).

CONCLUSION

These data show that laser therapy is an effective therapeutic option for all stages of severe twin-twin transfusion syndrome and provide information to counsel patients according to the stage of the syndrome.

Comparison of Pregnancy Course and Outcome with Color and Radiographic Angiography of the Placenta in a Monochorionic Triplet Pregnancy

A patient with spontaneous monochorionic (MC) triamniotic triplet pregnancy developed symptoms of feto-fetal-transfusion-syndrome (FFTS) at 18 weeks of gestation with one donor (oligohydramnios) and one receptor (polyhydramnios) triplet. The patient "received" a diet enriched with proteins. Amniotic-fluid volume returned to normal after 24 weeks. At 32 weeks, a Cesarean section was performed due to intra-uterine growth restriction of the donor triplet. Post partum color injection and computer angiograms showed arterio-arterial (AA) anastomoses between all triplets. Deep arterio-venous (AV) anastomoses between the two triplets who had demonstrated with oligo- and polyhydramnios between 18 and 26 weeks were revealed by computer angiography that were not seen by placental color angiogram. Detailed analysis of placental vascular communications by use of color injection angiogram of the chorionic plate and computer angiogram demonstrating deep anastomoses beneath the chorionic plate helps to understand the individual pathophysiology and clinical course in patients with FFTS, which is even more complex in MC triplet compared to MC twin pregnancies.

Twin-to-twin transfusion syndrome, vein of galen malformation, and transposition of the great arteries in a pair of monochorionic twins: coincidence or related association?

The pathogenetic mechanisms leading to the development of congenital heart disease and congenital intracranial arteriovenous malformation are still unclear. We report on a monochorionic twin pregnancy with twin-to-twin transfusion syndrome (TTTS), in which vein of Galen malformation (VGM) was diagnosed in the donor twin and transposition of the great arteries (TGA) in the recipient twin. The development of TTTS, VGM, and TGA in a single monochorionic pregnancy could be pure coincidence, but there might also be a causative link. We discuss the possible contribution of genetic factors, fetal flow fluctuations, vascular endothelial growth factors, and the process of twinning itself to the development of these congenital anomalies.

Monochorionic diamniotic infants without twin-to-twin transfusion syndrome

BACKGROUND

Monochorionic-diamniotic twins (MoDi) occur in 0.3% of all pregnancies. Twin-to-twin transfusion syndrome (TTS) that occurs in 20% of MoDi pregnancies is associated with high perinatal morbidity and mortality. MoDi twins without TTS are more frequent (80%) but have been scarcely reported.

OBJECTIVE

To study perinatal morbidity and mortality of 74 MoDi twin sets without TTS and to compare it to that of 38 sets of MoDi twins with TTS.

METHODS

Chorionicity was determined by gender and placental examination. Gestational age (GA) was set by sonography and pediatric examination. TTS was diagnosed clinically and by sonography, discordance was defined by twins birth weight difference > or =20%, and fetal growth restriction was determined by using a twin-specific nomogram.

RESULTS

MoDi twin pregnancies without and with TTS were similar in demographics, live births, history of preeclampsia, fetal distress and cesarean delivery. They were different (p<0.01) in discordant pregnancies (36 and 79%), GA at delivery (32 and 29 weeks) intrauterine growth restriction (39 and 89%) and neonatal mortality (12 and 36%). Concordant (47 sets) and discordant (27 sets) MoDi twins without TTS were clinically similar.

CONCLUSIONS

MoDi twins without TTS have high rates of birth weight discordance, fetal growth restriction, fetal distress, prematurity and cesarean delivery. Although their perinatal mortality is low, the reported occurrence and the short- and long-term impacts of fetal and neonatal morbidities warrants attention.

Paradoxic activation of the renin-angiotensin system in twin-twin transfusion syndrome: an explanation for cardiovascular disturbances in the recipient

Despite advances in treatment, twin-to-twin transfusion syndrome (TTTS) still carries a high risk for perinatal mortality and morbidity. Simple blood transfer from the donor to the recipient twin cannot explain all of the features of this disease, in particular the recipient's hypertensive cardiomyopathy. We report a case in which TTTS resulted in preterm delivery with early neonatal death of both twins, allowing assessment of the renin angiotensin system (RAS) status of each fetus, both by cord blood renin and aldosterone assay and by renal immunohistochemistry. The donor had severe oliguria/oligohydramnios, whereas the recipient, in addition to severe polyuria/polyhydramnios, had cardiomyopathy, atrioventricular regurgitation, and ascites. Although immunohistochemistry demonstrated that renal secretion of renin was up-regulated in the donor and down-regulated in the recipient, cord blood levels of renin and aldosterone were similar, with high renin levels in both twins. This observation supports the hypothesis that despite renal RAS down-regulation, the recipient is exposed to RAS effectors elaborated in the donor and transferred via placental shunts. This may contribute to cardiomyopathy and hypertension in the recipient, which cannot be accounted for by hypervolemia alone. We thus hypothesized that in TTTS, the recipient's hypertensive cardiomyopathy could be due to a mechanism similar to the classical model of hypertension referred to as "2 kidneys-1 clip." Thus the hypovolemic donor twin, comparable to the clipped kidney, produces vasoactive hormones that compromise the recipient, comparable to the normal kidney, causing hypertension and cardiomyopathy.

Histomorphometric characterisation of shared and non-shared cotyledonary villus territories of monochorionic placentae in relation to pregnancy complications

OBJECTIVE

Theoretical estimates and physiological inferences suggest that the structure of a shared cotyledon differs from a non-shared cotyledon. The aim of this study was to characterise the histomorphometry of terminal villi in shared and non-shared cotyledons in monochorionic placentae, both from uncomplicated twins and from those with twin-twin transfusion syndrome (TTTS) or discordant growth restriction (DeltaIUGR).

METHODS

Forty-one monochorionic placentae from Caucasian non-smokers were obtained at caesarean section. Their vascular anatomy and placental territories were ascertained by dye injection. After fixation, full thickness histological blocks were obtained by systematic random sampling from each twin's territory and the shared cotyledons. Fifty randomly selected terminal villi were assessed for: (i) median villus diameter (ii) median villus capillary diameter (iii) median fetomaternal diffusion distance (iv) median no. of capillaries/villus (v) degree of vascularization (median percentage cross-sectional area of terminal villi occupied by capillaries) using a stage micrometer and image analysis programme. The histomorphometric findings were then correlated with birthweight discordance, placental territory discordance and DeltaAVAs (no. of AVAs from smaller twin (donor) to larger twin (recipient) minus no. of AVAs from larger to smaller twin).

RESULTS

Histomorphometric variables were similar in shared and non-shared cotyledons of uncomplicated MCDA twins. However, the median diameter of terminal villi in shared cotyledons in DeltaIUGR and TTTS placentae was significantly smaller [51.2 microm (48.2-58.3), p<0.001 and 52.6 microm (53.1-50.4), p<0.001], and had a similar number of smaller capillaries, larger fetomaternal diffusion distance and reduced vascularization compared to non-shared IUGR and TTTS placentae. However, Deltadiameter (defined as the difference between median diameters of terminal villi in large minus small twins' territories) rose with increasing birthweight discordance (Pearson correlation coefficient=0.82, p<0.001). Multiple linear regression analysis revealed that Deltadiameter was influenced by placental territory discordance (p<0.001) and birthweight discordance (p<0.01): log10 Deltadiameter=1.38+(0.01 x birthweight discordance)+(0.56 x log10 placental territory discordance) (R2=0.82, p<0.001), but there was no significant relationship with DeltaAVA and AAA. In the TTTS group, Deltadiameter correlated significantly with DeltaAVA only: log10Deltadiameter=1.44+(0.02 x DeltaAVA) (R2=0.3, p<0.001).

CONCLUSIONS

This is the first study to characterise the histomorphometry of shared and non-shared cotyledons in MC twins. The findings suggest that abnormal placentation, rather than placental vascular anatomy may be responsible for DeltaIUGR in MC twins, whereas TTTS arises from imbalance in interfetal transfusion with resultant differing terminal villus histomorphometric features in donor, recipient and shared cotyledons.

Vascular Distribution Patterns in Monochorionic Twin Placentas

Several recent publications have focused on the association between the occurrence of twin-to-twin transfusion syndrome (TTTS) in diamniotic-monochorionic twins and the presence of a number of selected anatomic placental characteristics (distribution of vascular territory, cord insertion, type and number of inter-twin anastomoses). In contrast, the potential importance of the vascular distribution patterns of the individual twins remains to be elucidated. Based on its gross architectural distribution pattern, chorionic vasculature is traditionally described as disperse, magistral or mixed. The aim of this study was (1) to determine the relative prevalence of these vascular distribution patterns in monochorionic twin placentas, and (2) to correlate these patterns with the presence of TTTS and known anatomic placental features linked to TTTS. The placentas of 89 consecutive diamniotic-monochorionic twins (15 with TTTS, 74 without TTTS), examined at Women and Infants Hospital, were studied. Disperse vascular patterns were seen in 53% of twins, and magistral or mixed patterns in 47%. The prevalence of magistral/mixed vascular patterns was significantly higher in TTTS gestations than in non-TTTS gestations (60% versus 44%, P<0.05) and, in TTTS gestations, much higher in donor twins than in recipient twins (87% versus 33%, P<0.005). A strong association was found between the presence of magistral/mixed patterns and marginal/velamentous cord insertion, low number of inter-twin anastomoses, and uneven distribution of the vascular territories. These findings suggest that the magistral/mixed vascular distribution pattern may represent an important placental architectural feature contributing to the complex pathophysiology of TTTS.

Feto-feto-fetal transfusion syndrome in monozygotic monochorionic triamniotic triplets: vascular evaluation by a cast model

A unique cast model of the placenta in a rare case of feto-feto-fetal triplet transfusion syndrome (FFFTTS) allowed the demonstration of why the transfusion syndrome developed in one fetus and not in the other two in that single placenta. The vasculature anatomy of a monochorionic triamniotic triplet placenta with FFFTTS of three healthy infants (one donor, two recipients) born in the 35th week of gestation was cast by means of dental casting materials. After the cast hardened, the tissue was corroded, revealing the cast blood vessels. The diameters and lengths of the chorionic blood and intraplacental vessels of the cast placenta were measured with a digital caliper. The cast revealed two artery-artery (A-A) anastomoses on the chorionic plate between the two recipients and the donor. Seven artery-vein (A-V) deep anastomoses connected only the arteries of the donor and the veins of the two recipients. The blood vessel connections among the fetuses allowed the evaluation of a pathologic case with its own control in a single placenta. From the vascular appearance, we speculate that the A-A anastomoses between the two fetuses protected them from developing blood transfusions, but that the A-V anastomoses contributed to their development.

Characterisation of deep arterio-venous anastomoses within monochorionic placentae by vascular casting

OBJECTIVE

To characterise arterio-venous anastomoses (AVA) in monochorionic (MC) placentae and determine (i) whether shared cotyledons lie beneath the co-termination of an artery from one twin and a vein to the contralateral twin and (ii) whether all AVA can be detected by visual inspection of the chorionic plate.

METHODS

Vascular casts were made of 15 MC placentae. The number of typical AVAs suspected visually before digestion was compared with the number of AVAs identified after acid digestion.

RESULTS

Thirty-three of 67 (49%) suspected typical AVAs were confirmed as typical after casting. There were five false positives and no false negatives. The remainder were classified as atypical AVAs, found in > or =90% of MC placentae. Type I (small vascular connections between two apparently normal cotyledons not seen before casting) and Type II (shared cotyledons arising within larger apparently normal cotyledons) atypical AVAs were found in 53% and 73% of placentae, respectively.

CONCLUSIONS

Only half the shared cotyledons in MC placentae are characterised by co-termination of an artery and vein on the chorionic plate. We report the existence of deep anastomoses beneath the chorionic plate that cannot be visualised by chorionic plate inspection. These findings have implications for laser treatment of twin-twin transfusion syndrome.

Intratwin arteriovenous fistula of the placenta in a case of twin-to-twin transfusion syndrome

Arteriovenous fistulas of the placenta are extremely rare in singleton pregnancies and, to our knowledge, have not previously been reported in twin gestations. We describe a case of an arteriovenous fistula of the placenta in a diamniotic-monochorionic twin pregnancy complicated by twin-to-twin transfusion syndrome (TTTS). The arteriovenous fistula was demonstrated by color-coded vascular injection studies of the placenta. We speculate that the hemodynamic effects of the fistula may have contributed to the refractoriness of the TTTS to serial amniodrainages and laser ablation of communicating intertwin vessels.

Fetoscopic surgery in triplet pregnancies: a multicenter case series

OBJECTIVE

The purpose of this study was to evaluate the feasibility of fetoscopic surgery in complicated monochorionic and dichorionic triplet pregnancies.

STUDY DESIGN

This was a case series of fetoscopic surgery in 12 cases of monochorionic (n = 5) or dichorionic (n = 7) triamniotic triplets complicated by severe feto-fetal transfusion (n = 8), twin reversed arterial perfusion sequence (n = 3), or discordant for an anomaly (n = 1). Six underwent cord occlusion, and 6 had laser coagulation of the vascular anastomoses.

RESULTS

All procedures were successfully completed, and the outcome was comparable to that reported for similar procedures in twins. Eighty-three percent of fetuses survived, and 13% had long-term problems.

CONCLUSION

Fetoscopic surgery may be considered as a therapeutic option in complicated triplet pregnancies, with results similar to those found in twins.

The progression of disease stage in twin-twin transfusion syndrome

OBJECTIVE

To estimate the frequency of progression or regression of disease stage in pregnancies complicated by twin-twin transfusion syndrome (TTTS) managed with non-placental laser techniques.

METHODS

A cohort of TTTS pregnancies within the sole perinatal center for the state of Western Australia was examined. All cases of prenatally identified TTTS from 1992 to 2002 were staged at diagnosis (retrospectively prior to 2000, prospectively since). Amnioreduction and septostomy were the principal therapies used. Features associated with progression, regression or stability were identified.

RESULTS

During the study period, 71 cases of TTTS were managed. Amnioreduction was performed in 73.2%, with no difference in the median number of procedures by stage (p = 0.178). In 21.1% of cases, TTTS resolved completely with persistent normalization of amniotic fluid volumes after amnioreduction (median number of procedures: 2). Disease resolution was associated with pregnancy prolongation, greater gestational age at delivery (36 weeks vs. 28.4 weeks, p < 0.001) and increased perinatal survival (100% vs. 42.6%, p < 0.001) compared with stage progression. Logistic regression analysis predicted that the probability of both infants surviving was 80% if the pregnancy remained at Stage I or II throughout, compared with a probability of 50% if it reached Stage III or more at 26 weeks, and only 25% if the disease reached Stage III or more at 16 weeks' gestation.

CONCLUSION

Pregnancy outcome for TTTS managed with amnioreduction techniques is correlated with stage at diagnosis and the subsequent disease evolution. However, the progression of stage in TTTS is unpredictable and the likelihood of spontaneous fetal demise was not different between stages.

Pseudo-arterio-arterial anastomoses in twin–twin transfusion syndrome

OBJECTIVE

It has recently been claimed that fetoscopic recognition of a haemodynamic equator within an arterio-arterial anastomosis (AAA) suggests minimal net intertwin flow. This was based on blood from one fetus being dark and from the other bright red, the boundary between them reciprocating with the fetal heart beats. However, bright red indicates that the blood had passed through a cotyledon and been freshly oxygenated, which should be impossible in an AAA. We applied a computer model of chorionic vessels to determine a configuration that reproduced this phenomenon.

METHODS

A previously published TTTS model was extended to provide placental detail in a segment containing four cotyledons of each placenta supplied by three generations of placental arteries and veins.

RESULTS

Reciprocating flow is not unique to AAAs. It also occurs in the chorionic arteries of any cotyledon deprived of its venous outflow, in a similar manner to that in which reverse end-diastolic flow occurs in umbilical arteries when whole placental resistance is high. If venous return from the common chorionic vein in the recipient (draining the venous end of an AVA) is blocked as might happen after laser, there can be bidirectional flow from one umbilical artery insertion, through two cotyledons to the other insertion. We define this phenomenon as a pseudo-AAA (PAAA). The inclusion of two cotyledons in this path means that its resistance cannot match the low flow resistance of a true AAA, and transmission of the contralateral pulsatile pattern is absorbed in the cotyledons. Thus, PAAA Doppler patterns differ from true AAA patterns in that two sets of systolic peaks, one forward and one reverse, can be discerned in true AAAs but only one in PAAAs.

CONCLUSIONS

We demonstrate how venous occlusion of an arterio-venous anastomosis may produce a pseudo-AAA colour equator at endoscopy. However, visual observation of reciprocating flow is not sufficient to define a vessel as a true AAA which instead requires ultrasonical identification of two systolic patterns.

First-Trimester Findings Associated with Twin Reversed Arterial Perfusion Sequence

INTRODUCTION

Regarding its pathogenesis, discordant development in early gestation, as well as vascular anastomoses between twins are postulated to be required for the establishment of the twin-reversed arterial perfusion (TRAP) sequence. However, first trimester findings associated with this complication have not yet been reported.

CASE

A discordant monochorionic twin was revealed upon examination of a 24-year-old primigravida at 11 weeks' gestation. Cystic masses were identified on the back of the smaller twin, later followed by the appearance of skin edema and pericardial effusion, indicating cardiac failure. Subsequently, despite diagnosis of fetal demise at 15 weeks the lower body was shown to have further developed and the heartbeats appeared again, resulting in an acardia anceps or hemicardia. No remarkable change was observed in the larger normal twin.

CONCLUSION

This occurrence was considered consistent with the current hypothesis regarding the pathogenesis of the acardiac anomaly. First trimester discordancy in a monochorionic twin gestation is considered to represent an early manifestation of TRAP sequence.

Occlusion of Arterio-Arterial Anastomosis Manifesting as Acute Twin–Twin Transfusion Syndrome

In vivo, ex vivo and modelling studies suggest that arterio-arterial anastomoses (AAAs) protect against haemodynamic imbalance in monochorionic twins and thus the development of TTTS. We report the acute onset of severe TTTS at 34 weeks' gestation in a patient with an antenatally visualized AAA which was shown at injection studies to have been obliterated, presumably by thrombosis. Computer modelling with the relevant clinical data confirmed that occlusion of the AAA alone was sufficient to reproduce the clinical manifestations. A study of the vascular configuration of AAA in the fixed placenta suggested that its small diameter and turbulent flow may have contributed to its occlusion. This case report shows that the unmasking of unbalanced AVA configurations by occlusion of a protective AAA can manifest as TTTS.

Monoamniotic-versus diamniotic-monochorionic twin placentas: anastomoses and twin-twin transfusion syndrome

OBJECTIVE

The purpose of this study was to compare monoamniotic-monochorionic and diamniotic-monochorionic twin placentas and to estimate the incidence of twin-twin transfusion syndrome in monoamniotic-monochorionic twin pregnancies.

STUDY DESIGN

We analyzed the angioarchitecture and cord insertion distance in 24 monoamniotic-monochorionic and 200 diamniotic-monochorionic placentas.

RESULTS

Compared with diamniotic-monochorionic placentas, monoamniotic-monochorionic placentas had significantly more arterioarterial anastomoses (20/20 vs 159/200, respectively; P=.013), significantly less opposite arteriovenous anastomoses (10/20 vs 165/200, respectively; P=.002), similar venovenous anastomoses (6/20 vs 46/200, respectively; P=.323), and arteriovenous anastomoses (20/20 vs 187/200 respectively; P=.279) and significantly shorter umbilical cord distances (median [+/-SD], 5.0+/-6.9 cm vs 17.5+/-6.8 cm; P<.001).

CONCLUSION

Monoamniotic-monochorionic and diamniotic-monochorionic placentas have different anastomotic patterns. The (virtually) 100% incidence of arterioarterial anastomoses in monoamniotic-monochorionic placentas explains the reason that twin-twin transfusion syndrome rarely occurs in monoamniotic-monochorionic twin pregnancies and predicts that twin-twin transfusion syndrome manifestations are approximately 5 times less often recognized in monoamniotic-monochorionic pregnancies than in diamniotic-monochorionic pregnancies.