Monochorionic Twin Placentas Research Articles

Twin to Twin Transfusion Syndrome

Introduction: Collateral arterial growth is an effective adaptation process to maintain blood supply in myocardial tissue distal to a coronary stenosis and in other vascular beds where feeding arteries are obstructed (1) . The drive for outgrowth and remodelling of arterial collaterals is an increased shear stress due to an enlarged blood flow occurring after the event of stenosis in a near by conduit artery. Remodelling includes increased growth of the diameter and length of the collateral, causing the characteristic tortuous or cork screw appearance (1) .Whilst collateral growth is generally beneficial, we will present evidence that arterial collateral out growth occurred in a monochorionic twin placenta where it jeopardised the pregnancy by causing the twin to twin transfusion syndrome (TTTS).Objective: to report a case of twin-to-twin transfusionCase Report: Reporting a case experienced and taken care in our Clinic Fetomaternal RS. Dr .M. Jamil Hospital. A 34 years old woman, gravida 2, para1, at 31 weeks and 6 days amenorrhea, because her pregnant uterus was too large for gestational Referral to tertiary center followed. At 32 weeks and 2 days amenorrhea biometry indicated estimated fetal weights of 1950 and 1450 g (Hadlock), oligohydramnios and polyhydramnios (amniotic fluid index:23cm. No structural anomaly of the heart was seen. No interventions, one course of corticosteroids were administered for fetal lung maturation. At 33 weeks a slight decrease in heart rate variability of the smaller twin was observed. A Caesarean section under spinal anesthesia was performed. Two girls were delivered of 1585 g and 2135 g and in good condition (Apgar scores 8 and 9 after 1 and 5 min in both girls). The monochorionic diamniotic placenta weighed 740 g. The cord of the recipient was centrally inserted and that of the donor velamentally. Placenta was born monochorion, diamnion.Conclusion: TTTS is caused due to unidirectional deep arteriovenous (AV) anastomoses with the superficial short comings. Hypovolemia, oliguria and oligohydramnion occurs in the donor fetus. Hypervolemia, polyuria and polyhydramnios occurs in the recipient fetus

Are there differences between monochorionic twin placentas after spontaneous and assisted conception?

IntroductionNo data are available on the placental characteristics of monochorionic twin pregnancies conceived by in vitro fertilization (IVF). This study investigates the differences between placentas from monochorionic diamniotic (MCDA) twin pregnancies conceived spontaneously and those conceived after IVF. MethodsThis is a retrospective analysis of placental data from a consecutive series of MCDA twin pregnancies followed from the first trimester. The following placental characteristics were compared between IVF versus spontaneous MCDA pregnancies: placental sharing and birth weight discordance relative to placental sharing, the placental angioarchitecture (number, type, and size of anastomoses), and the umbilical cord insertion types. ResultsOf the 256 MCDA placentas included in this analysis, 32 (12%) were conceived through IVF and 224 (88%) spontaneously. MCDA twin placentas after IVF did not differ significantly from MCDA twin placentas after spontaneous conception regarding placental sharing, birthweight discordance relative to sharing discordance, and angioarchitecture. There was a trend toward more discordant cord insertions (combination eccentric and velamentous) in IVF (25%) than in spontaneously conceived placentas (12%) (P = 0.05). DiscussionNo differences could be demonstrated between MCDA placentation after spontaneous conception and IVF. Any differences in pregnancy outcome between spontaneous and IVF conceived MCDA twins may not be related to differences in placental sharing, angioarchitecture and cord insertion type.

The association between vein-to-vein anastomoses and birth weight discordance in relation to placental sharing in monochorionic twin placentas.

This study aims to examine the association between the presence and size of a vein-to-vein (VV) anastomosis and birth weight discordance relative to placental discordance in monochorionic diamniotic twin pregnancies. Placentas of two previous prospective studies were included in this retrospective analysis. After injection with color dye, we measured the placental surface of each twin and VV, artery-to-artery (AA), and artery-to-vein (AV) anastomoses on a digital photograph. We calculated the birth weight ratio (BWR), placental ratio (PR), and birth weight ratio/placenta ratio (BWR/PR), as well as total AV size and net AV transfusion. Placental characteristics were compared between placentas with and without VV anastomoses. We performed univariate analyses to assess the following predictors for BWR/PR: VV size, AA size, total AV size, and net AV transfusion. Multivariate analysis was then performed, including the variables significant in univariate analysis. We analyzed 247 placentas: 58 (23%) with VV anastomoses and 189 without (77%). The BWR and PR were higher in the group with VV. In contrast, BWR/PR was lower in the group with VV anastomoses than in those without. The size of AA anastomoses was larger in placentas with VV anastomoses than in those without. In univariate analysis, VV size and AA size were significantly associated with BWR/PR. However, in multivariate regression, only VV size remained significantly associated with the BWR/PR. VV anastomoses are associated with a decreased birth weight discordance relative to the placental sharing discordance, independent of the AA anastomoses.

Comparison of the ratio of placental territory discordance to birthweight discordance in placentas of monochorionic diamniotic twins.

The ratio of placental territory discordance to birthweight discordance was calculated in monochorionic diamniotic twin placentas. We then determined whether the ratio: (1) correlated with the overall diameter of the placental superficial vascular anastomoses and (2) was different in normal monochorionic diamniotic twin (normal MCDA), twin-to-twin transfusion syndrome (TTTS), and selective intrauterine growth restriction (sIUGR) pregnancies. A prospective study of MCDA placentas was conducted from April 1, 2016, to April 1, 2019, including three groups, normal MCDA (N = 49), TTTS (N = 38), and sIUGR (N = 52). Placentas were studied via dye injection. In the normal MCDA, sIUGR, and TTTS groups, the ratio positively correlated with the overall diameter of the placental superficial vascular anastomoses (Spearman's = 0.295, 0.619, and 0.530; p = 0.040, <0.001, and 0.001, respectively) and gradually decreased from normal MCDA to sIUGR and to TTTS (2.88 (0.34, 64.25), 1.70 (0.27, 4.52), and 1.03 (0.12, 15.17); p < 0.001, p = 0.016/<0.001/0.005, respectively). The placental territory discordance to birthweight discordance ratio is an effective index reflecting the overall vascular anastomoses in MCDA placentas.

The vascular equator in monochorionic twin placentas

IntroductionWe aim to examine the location of the vascular equator according to the umbilical cord insertions in monochorionic twin placentas. MethodsWe combined two prospective series of monochorionic diamniotic twin placentas of patients included in the first trimester between 2004 and 2008, and between 2016 and 2019. We injected the placentas after birth and divided them into three groups, with respectively concordant (eccentric-eccentric, marginal-marginal, and velamentous-velamentous), intermediate (eccentric-marginal and marginal-velamentous) and discordant (eccentric-velamentous) cord insertions. For each unidirectional anastomosis, we determined the cord-anastomosis ratio and then calculated the mean ratio per placenta in each group. We also calculated the deviation from the midline in all groups. Results195 placentas were included. In concordant placentas, the mean cord-anastomosis ratio was 0.957 (95% CI [0.908–1.009]). In placentas with intermediate discordance, the mean ratio was 0.886 (95% CI [0.828–0.948]) and in discordant placentas it was 0.797 (95% CI [0,708–0.897]) (p < 0.001). In concordant placentas, the equator was in the middle of the cord insertions with an average deviation of 0.2 cm (95% CI [-0.1 – 0.3]). In the intermediate placentas, the equator deviated on average 0.5 cm (95% CI [0.2–0.8]) and was displaced from the middle towards the most central cord insertion. In discordant placentas, there was an average displacement of 1.0 cm (95% CI [0.50–1.6]). DiscussionIn concordant placentas, the vascular equator lies in the middle between both cord insertions. In intermediate and discordant placentas, the equator is closer to the more central cord insertion.

Comparison of Mannequin Training Satisfaction with a Conventional Box Trainer and a Low-Fidelity Fetoscopic Surgical Simulator for Selective Fetoscopic Laser Photocoagulation

Background: A low-fidelity fetoscopic surgical simulator (FSS) for training of selective fetoscopic laser photocoagulation (SFLP) was developed. Objective: To evaluate and compare training satisfaction with an FSS and with a conventional box trainer (BT). Methods: The BT consisted of a cleaned human placenta attached to the inside of a plastic storage box with a watertight lock cover and an ultrasound-transparent rubber skin. The FSS consisted of the replica of a monochorionic twin placenta attached to the inside of a spherically shaped, ultrasound-transparent phantom. Tap water was used as an ultrasound conduction agent. Evaluation of the mannequin trainings was conducted on 8 junior maternal-fetal medicine (MFM) attending physicians and 22 MFM fellows. Training satisfaction was scored from 0 to 10 on 8 different domains. Results: The mean satisfaction score (±SD) with the FSS was higher than with the BT in all domains (p < 0.05). The fellows’ training satisfaction with the BT was greater than that of the attending physicians in 4 domains: tactile feedback, demonstration of chorionic vessels, feedback on performance, and overall value as learning aid (p < 0.05). Conclusions: As evaluated by a small group of trainees, our FSS is superior to the BT in mannequin training of SFLP. However, the BT may be more useful for trainees with limited clinical experience.

Redness discordance in monochorionic twin placentas: Correlation with clinical and placental findings

Introduction/ObjectivesRecent studies suggest redness (color) discordance of the placental basal plate may be a marker for twin anemia-polycythemia sequence (TAPS), a recently described complication of diamniotic-monochorionic twinning characterized by marked intertwin hemoglobin (Hb) discordance in the absence of oligohydramnios-polyhydramnios. In this study, we determined the clinicoplacental and choriovascular correlates of basal plate color discordance in monochorionic twin placentas, and assessed its value as postnatal indicator of TAPS. MethodsWe performed a clinicoplacental analysis of 100 consecutive non-TTTS diamniotic-monochorionic twin placentas with available photographic documentation of the basal plate. Basal plate redness was quantified by computer-assisted analysis of digital images and expressed as intertwin color difference ratio (CDR). ResultsThe CDR ranged between 1.00 and 3.58 (median CDR: 1.14; 90th %ile: 1.98). Compared to twins with low CDR (N = 90), twins with high CDR (≥2.0; N = 10) had significantly higher hemoglobin difference (11.25 g/dL versus 2.55 g/dL) and significantly fewer and smaller artery-to-artery (AA) and artery-to-vein (AV) anastomoses. Apgar scores and birth weights were equivalent in both groups. Among the 10 twin sets with high CDR, six (60%) qualified as TAPS, as defined by intertwin Hb difference >8 g/dL and absent or very small AA and AV anastomoses. Conversely, 6 of 8 (75%) twin sets with TAPS had a CDR ≥ 2.0. CONCLUSIONIntertwin CDR correlates with intertwin hemoglobin difference and chorionic angioarchitecture. A CDR value ≥ 2.0 (the 90%ile value for CDR derived from the present cohort) has high specificity (96%), but relatively low positive predictive value (60%) as indicator of TAPS, as currently defined.

The History of Treatment of Twin-to-Twin Transfusion Syndrome.

Historical suggestions of twin-to-twin transfusion syndrome (TTTS) date back to the early 17th century. Placental anastomoses were first reported in 1687; however, it was Schatz who first identified their importance in 1875. He recognized 'the area of transfusion' within the 'villous district' of the placenta, which he named the 'third circulation'. This article describes how the management of TTTS has evolved as we have gained a more sophisticated understanding and appreciation of the complex vascular anastomoses that exist in monochorionic twin placentae. Currently, fetosopic laser occlusion is the preferred treatment option for TTTS.

The promoter methylomes of monochorionic twin placentas reveal intrauterine growth restriction-specific variations in the methylation patterns.

Intrauterine growth restriction (IUGR) affects the foetus and has a number of pathological consequences throughout life. Recent work has indicated that variations in DNA methylation might cause placental dysfunction, which may be associated with adverse pregnancy complications. Here, we investigated the promoter methylomes of placental shares from seven monochorionic (MC) twins with selective intrauterine growth restriction (sIUGR) using the healthy twin as an ideal control. Our work demonstrated that the IUGR placental shares harboured a distinct DNA hypomethylation pattern and that the methylation variations preferentially occurred in CpG island shores or non-CpG island promoters. The differentially methylated promoters could significantly separate the IUGR placental shares from the healthy ones. Ultra‐performance liquid chromatography/tandem mass spectrometry (UPLC‐MS/MS) further confirmed the genome‐wide DNA hypomethylation and the lower level of hydroxymethylation statuses in the IUGR placental shares. The methylation variations of the LRAT and SLC19A1 promoters, which are involved in vitamin A metabolism and folate transportation, respectively, and the EFS promoter were further validated in an additional 12 pairs of MC twins with sIUGR. Although the expressions of LRAT, SLC19A1 and EFS were not affected, we still speculated that DNA methylation and hydroxymethylation might serve a functional role during in utero foetal development.

Color Difference in Placentas with Twin Anemia-Polycythemia Sequence: An Additional Diagnostic Criterion?

Objective: To determine the color intensity difference between the 2 placental shares in monochorionic placentas with twin anemia-polycythemia sequence (TAPS). Methods: We evaluated all digital pictures of TAPS placentas examined at our center and compared them to a control group of uncomplicated monochorionic placentas. We determined the color intensity of individual placental share on the maternal side of each monochorionic placenta using an image processing program and calculated the color difference ratio (CDR). Results: Digital pictures of 19 TAPS and 19 uncomplicated monochorionic placentas were included in this study. The TAPS group consisted of 12 spontaneous TAPS placentas (63%) and 7 post-laser TAPS placentas (37%). The median CDR in the group with TAPS was significantly higher than in the control group, 2.73 (range 1.73-6.36) versus 1.09 (range 1.00-1.35), respectively (p < 0.01). We found a positive correlation between CDR and inter-twin hemoglobin (Hb) difference in the TAPS group (R = 0.66, p < 0.01) but not in the control group (R = 0.04, p = 0.87). Conclusion: TAPS placentas have a significantly higher CDR compared to uncomplicated monochorionic twin placentas. Large inter-twin Hb differences in TAPS are associated with higher CDR.

Umbilical Cord Coiling and Zygosity: Is there a Link?

Introduction: The aim of this study was to analyze abnormalities of umbilical coiling index (UCI) in twin gestation to test whether the coiling is genetically influenced by zygosity.Methods: Data retrieved comprised gestational age (GA), chorionicity, fetal gender, and UCI. Results: The mean UCI of hypercoiled cords in monochorionic placentas was 0.55 coils/cm and 0.49 coils/cm in dichorionic placentas with discordant fetal gender (P = 0.2629).Discussion: In conclusion, no significant statistical difference between UCI in monochorionic and dichorionic twin placentas with discordant fetal gender was identified, suggesting that zygosity does not play a role in umbilical coiling induction.

Color-dye injection of monochorionic placentas and correlation with pregnancy complications

IntroductionVascular anastomoses in monochorionic (MC) twin placenta can be easily identified with color-dye injection. The aim of this study is to analyze the relationship between different type of anastomoses and twin pregnancy complications. MethodsFrom January 2011 to October 2014, MC placentas were analyzed with color-dye injection and five group of pregnancies were identified: those that were not complicated (NC), those complicated with selective intrauterine growth restriction (sIUGR), twin–twin transfusion syndrome (TTTS), or twin anemia-polycitemia sequence (TAPS) and those with amniotic fluid discordance (AFD) between twins. Cases of TTTS treated with endoscopic laser coagulation of placenta anastomoses or cases with in utero death of one twin were excluded. ResultsA total of 118 MC placentas were observed, 58 (49%) NC, 35 (30%) sIUGR, 10 (8%) TTTS, 13 (11%) AFD and 2 (2%) TAPS. The median number of anastomoses was 7 (range 1–15), 8 (2–18), 4 (2–11), 7 (2–13) and 1 (1–1), respectively. At least one artero-venous anastomoses was found in the placenta observed, while the prevalence of artero-arterial anastomoses was 95% for NC, 91% for sIUGR, 60% for TTTS, and 77% for AFD; no TAPS placenta had this type of anastomoses. The diameter of arteroarterial anastomoses was greater in the AFD group (3.3 mm), compared to the NC, sIUGR and TTTS groups (2.3, 2.5 and 1.4 respectively, p 0.04). DiscussionIn this large serie of MC placenta analyzed with color-dye injection, a specific distribution of anastomoses emerged for twins with amniotic fluid discordance, which points to a need for intensive surveillance.

Veno–venous anastomoses in twin–twin transfusion syndrome: A multicenter study

IntroductionThe aim of this study is to evaluate the prevalence of veno–venous (VV) anastomoses in a large cohort of monochorionic (MC) twin placentas with twin–twin transfusion syndrome (TTTS) compared to a control group of MC placentas without TTTS. MethodsAll TTTS placentas not treated with fetoscopic laser surgery (TTTS group) and examined at five international fetal therapy centers were included in this study and compared with a control group of MC placentas without TTTS (non-TTTS group). MC placentas were routinely injected with colored dye. We recorded the presence of VV and arterio-arterial (AA) anastomoses. ResultsA total of 414 MC placentas were included in this study (TTTS group, n = 106; non-TTTS group, n = 308). The prevalence of VV anastomoses was significantly higher in the TTTS group than in the non-TTTS group, 36% (38/106) and 25% (78/308), respectively (p = .04; odds ratio (OR) 1.65; 95% confidence interval (CI): 1.03–2.64). In the subgroup of MC placentas without AA anastomoses, the prevalence of VV anastomoses in the TTTS group and non-TTTS group was 32% (18/57) and 8% (2/25), respectively (p = .03; OR: 5.31; 95% CI: 1.13–24.98). DiscussionVV anastomoses are detected more frequently in TTTS placentas than in MC placentas without TTTS and may thus play a role in the development of TTTS.

Placental share and hemoglobin level in relation to birth weight in twin anemia-polycythemia sequence

IntroductionTwin anemia-polycythemia sequence (TAPS) is a newly described form of chronic twin transfusion. Previous observational studies noted a discordance between birth weight and individual placental share in TAPS. The purpose of this study was to investigate if fetal growth in monochorionic (MC) twins with TAPS is determined by placental share or by the net inter-twin blood transfusion. MethodsAll consecutive MC twin placentas of live-born twin pairs with and without TAPS examined at our center between June 2002 and February 2014 were included in this study. Hemoglobin (Hb) levels and individual placental share were evaluated at birth and correlated with birth weight share. We excluded MC twin pregnancies with twin–twin transfusion syndrome. ResultsA total of 270 MC twin pregnancies (TAPS group, n = 20; control group without TAPS, n = 250) were included in this study. Donors with TAPS had a lower birth weight than recipients in 90% (18/20) of cases, but a larger placental share in 65% (13/20) of cases. In the TAPS group, birth weight share was positively correlated with Hb share at birth (P < 0.01) but not with placental share (P = 0.54). In the control group without TAPS, birth weight share was strongly correlated with placental share (P < 0.01) but not with Hb share (P = 0.14). DiscussionA relatively larger placental share may enable the survival of the anemic twin in TAPS. ConclusionIn contrast with uncomplicated MC twins, fetal growth in MC twins with TAPS is determined primarily by the net inter-twin blood transfusion instead of placental share.

Vascular Network Features, Separate from Anastomotic Communications, Account for Birthweight Discordance in Monochorionic Placentas

s / Placenta 34 (2013) A1–A99 A13 P1.5. VASCULAR NETWORK FEATURES, SEPARATE FROM ANASTOMOTIC COMMUNICATIONS, ACCOUNT FOR BIRTHWEIGHT DISCORDANCE IN MONOCHORIONIC PLACENTAS Moni Kaneti , Enrico LoPriore , Nadav Schwartz , Dawn Misra , Carolyn Salafia 1,2 1 Placental Analytics LLC, Larchmont, NY, USA; 2 Institute for Basic Research, Staten Island, NY, USA; 3 Leiden University Hospital, Leiden, The Netherlands; University of Pennsylvania SChool of Medicine, Philadelphia PA, USA; Wayne State University, Detroit, MI, USA Goal: The goal of this study was to determine how circulatory anastomoses, structural features of features of the chorionic vascular networks, and umbilical cord inserted were correlated with differences between birth weights, and discordant weights (BWD) in monochorionic (MO) twins. Methods: De-identified images of 44 MO twin placentas with TTTS mild enough to not require laser ablation surgery in utero were traced to detail the arterial (A) and venous (V) networks for 45 pairs of MO twins. A traced placenta yields four images, one of each twin's A and V networks. Vessels 20% and 12 (27% with BWD>25%. All but 7(16%) twins had identifiable anastomoses connecting the two circulations. 32 (71%) had at least one AA anastomoses, while 26 (59%) had AV anastomoses. 8 (18%) had VV anastomoses. AA and VV anastomoses were uncorrelated with BWD. While the presence of any AV anastomoses (v. no AV anastomoses) was uncorrelated with BWD, increasing # AV anastomoses >1 VA anastomosis increased BWD 4.1% (p1⁄40.01) Network structures of larger and smaller twins differed significantly and accounted for 11% of BWD. Umbilical cord insertion site was not correlated in either twin with type or # of anastomoses (each p>0.10, data not shown). Abnormal cord insertions (coded normal, marginal and velamentous) was associated with more sparse surface vessels only in the smaller twin, (data not shown) and remained significant after controlling for the arterial branching density and # of AV anastomoses. Conclusion: Many features of the vascular networks, and particularly arterial networks, were strongly correlated with BWD, including Ă differences in total vascular surface area, branch generations and total number of branch points. Such differences in vascular network structures provide insight into the pathophysiology that can result in drastic differences in fetal development in MO twins. http://dx.doi.org/10.1016/j.placenta.2013.06.042 P1.6. PLACENTAL TERMINALVILLI COMPLEXITY IN CASES OF AUTISM/AUTISM SPECTRUM DISORDER (ASD) AND THEIR MATCHED CONTROLS Carolyn Salafia , George Merz , Craig Platt 3 1 Institute for Basic Research, Staten Island, NY, USA; 2 Placental Analytics LLC, Larchmont, NY, USA; University Hospitals Bristol NHS Foundation Trust,

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

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

What—and Why—the Pathologist Should Know about Twin-to-Twin Transfusion Syndrome

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

Placental characteristics in monochorionic twins with spontaneous versus post-laser twin anemia-polycythemia sequence

IntroductionTwin anemia-polycythemia sequence (TAPS) may occur in monochorionic twins either spontaneously or after laser surgery for twin–twin transfusion syndrome. Our aim was to analyze the placental angioarchitecture in spontaneous versus post-laser TAPS. MethodsWe included all monochorionic twin placentas with spontaneous or post-laser TAPS injected at our center between 2002 and 2012. Placental angioarchitecture was evaluated using colored dye injection. ResultsA total of 600 monochorionic placentas were injected during the study period of which 43 (7.2%) with TAPS (spontaneous TAPS, n = 16; post-laser TAPS, n = 27). Almost all anastomoses (96%; 119/124) were very small (diameter <1 mm) and the majority was localized near the placental margin. The median number of anastomoses per placenta was 4 (interquartile range (IQR): 3–5) in the spontaneous TAPS group and 2 (IQR: 1–3) in the post-laser TAPS group (p = 0.003). Arterio-arterial (AA) anastomoses were detected in 14.0% (6/43) of TAPS placentas and were all minuscule (diameter <1 mm). The rate of AA anastomoses in the spontaneous TAPS group and post-laser TAPS group was 18.8% (3/16) and 11.1% (3/27), respectively (p = 0.184). DiscussionSpontaneous TAPS placentas have a significantly higher total number of anastomoses compared to post-laser TAPS placentas. Most anastomoses were localized near the margins of the placenta. Minuscule AA anastomoses were detected sporadically in both groups and the rate of AA anastomoses is slightly higher in the spontaneous TAPS group than in the post-laser group. ConclusionSpontaneous TAPS placentas have a different placental angioarchitecture than post-laser TAPS placentas in terms of number and type of vascular anastomoses.

Placental endoglin levels in diamniotic-monochorionic twin gestations: Correlation with clinical and placental characteristics

ObjectiveWhile endoglin has been implicated in the pathogenesis of various complications in singleton pregnancies, its potential contribution to complications of monochorionic twinning remains largely undetermined. The aim of this study was to determine the correlation between relevant clinical and pathological variables and placental endoglin levels in diamniotic-monochorionic twin pregnancies. MethodsEndoglin expression was studied by immunohistochemistry and Western blot in a prospective cohort of 68 non-TTTS and 7 TTTS monochorionic twin placentas. Placental endoglin levels were correlated with clinical and placental characteristics associated with twin-to-twin transfusion syndrome (TTTS) and selective growth restriction, including birth weight discordance, uneven placental sharing, peripheral cord insertion and choriovascular anatomy. ResultsIn non-TTTS gestations discordant for these criteria, placental endoglin levels were significantly higher for the twin with smaller birth weight, intrauterine growth restriction, and/or abnormal ultrasound Doppler studies than for the more normal co-twin. Similarly, placental endoglin levels were significantly higher in the placental territory with smaller share and/or peripheral cord insertion in cases discordant for these placental characteristics. In TTTS gestations, placental endoglin levels tended to be higher for donor twins than for recipients. There was no correlation between endoglin levels and superficial choriovascular anastomoses. ConclusionsWhile the exact functional implications remain to be determined, our findings suggest a strong correlation between unbalanced placental endoglin levels and intertwin growth discordance in monochorionic twins.

Targeted Gene Arrays across the Severely-Discordant growth Monochorionic Twin Placenta: Implications for Angiogenesis and Metabolic Programming

Ziel: To explore angiogenesis and metabolic gene expression pathways in severe discordant monochorionic (MC) IUGR that may be subject to epigenetic regulation.