Consensus diagnostic criteria and monitoring of twin anemia-polycythemia sequence: Delphi procedure

Society for Maternal-Fetal Medicine Consult Series #72: Twin-twin transfusion syndrome and twin anemia-polycythemia sequence

Thirty percent of spontaneously occurring twins are monozygotic, of which two-thirds are monochorionic, possessing a single placenta. A common placental mass with shared intertwin placental circulation is key to the development and management of complications unique to monochorionic gestations. In this Consult, we review general considerations and a contemporary approach to twin-twin transfusion syndrome and twin anemia-polycythemia sequence, providing management recommendations based on the available evidence. The following are the Society for Maternal-Fetal Medicine recommendations: (1) we recommend routine first-trimester sonographic determination of chorionicity and amnionicity (GRADE 1B); (2) we recommend that ultrasound surveillance for twin-twin transfusion syndrome begin at 16 weeks of gestation for all monochorionic-diamniotic twin pregnancies and continue at least every 2 weeks until delivery, with more frequent monitoring indicated with clinical concern (GRADE 1C); (3) we recommend that routine sonographic surveillance for twin-twin transfusion syndrome minimally include assessment of amniotic fluid volumes on both sides of the intertwin membrane and evaluation for the presence or absence of urine-filled fetal bladders, and ideally incorporate Doppler study of the umbilical arteries (GRADE 1C); (4) we recommend fetoscopic laser surgery as the standard treatment for stage II through stage IV twin-twin transfusion syndrome presenting between 16 and 26 weeks of gestation (GRADE 1A); (5) we recommend expectant management with at least weekly fetal surveillance for asymptomatic patients continuing pregnancies complicated by stage I twin-twin transfusion syndrome, and consideration for fetoscopic laser surgery for stage I twin-twin transfusion syndrome presentations between 16 and 26 weeks of gestation complicated by additional factors such as maternal polyhydramnios-associated symptomatology (GRADE 1B); (6) we recommend an individualized approach to laser surgery for early- and late-presenting twin-twin transfusion syndrome (GRADE 1C); (7) we recommend that all patients with twin-twin transfusion syndrome qualifying for laser therapy be referred to a fetal intervention center for further evaluation, consultation, and care (Best Practice); (8) after laser therapy, we suggest weekly surveillance for 6 weeks followed by resumption of every-other-week surveillance thereafter, unless concern exists for post-laser twin-twin transfusion syndrome, post-laser twin anemia-polycythemia sequence, or fetal growth restriction (GRADE 2C); (9) following the resolution of twin-twin transfusion syndrome after fetoscopic laser surgery, and without other indications for earlier delivery, we recommend delivery of dual-surviving monochorionic-diamniotic twins at 34 to 36 weeks of gestation (GRADE 1C); (10) in twin-twin transfusion syndrome pregnancies complicated by posttreatment single fetal demise, we recommend full-term delivery (39 weeks) of the surviving co-twin to avoid complications of prematurity unless indications for earlier delivery exist (GRADE 1C); (11) we recommend that fetoscopic laser surgery not influence the mode of delivery (Best Practice); (12) we recommend that prenatal diagnosis of twin anemia-polycythemia sequence minimally require either middle cerebral artery Doppler peak systolic velocity values >1.5 and <1.0 multiples of the median in donor and recipient twins, respectively, or an intertwin Δ middle cerebral artery peak systolic velocity >0.5 multiples of the median (GRADE 1C); (13) we recommend that providers consider incorporating middle cerebral artery Doppler peak systolic velocity determinations into all monochorionic twin ultrasound surveillance beginning at 16 weeks of gestation (GRADE 1C); and (14) consultation with a specialized fetal care center is recommended when twin anemia-polycythemia sequence progresses to a more advanced disease stage (stage ≥II) before 32 weeks of gestation or when concern arises for coexisting complications such as twin-twin transfusion syndrome (Best Practice).

Artery-to-vein anastomoses in unequally divided placentas and their association with birthweight discordance

INTRODUCTION

This study investigated the impact of the shared intertwin circulation in unequally divided monochorionic (MC) placentas on fetal growth.

METHODS

This retrospective analysis included color-dyed, unequally shared placentas from two tertiary centers. Exclusions included twin-twin transfusion syndrome, twin anemia polycythemia sequence, and lethal anomalies. Measurement of the external diameters and areas of the artery-to-artery (AA), artery-to-vein (AV), and vein-to-vein (VV) anastomoses was performed. The ratio of the shared circulation (AV ratio) was determined by comparing the areas of the summed venous components of shared AV anastomoses to those in the individual AV anastomoses of the smaller placental part. The birth weight ratio/placental ratio (BWR/PR), total AV size areas and net AV transfusion were calculated. Univariable and multivariable linear regressions were performed to assess the relationship between BWR/PR, the AV ratio, the areas of the different anastomoses and cord insertion discordance.

RESULTS

Among 352 placentas, 97 % (340) had intertwin AV anastomoses, and 50 % (176) were from pregnancies with selective growth restriction. The AV ratio, AA, VV, total AV areas, and cord insertion discordance negatively correlated with BWR/PR. Multivariable linear regression confirmed the independent negative association between BWR/PR and the AV ratio, suggesting that a larger shared circulation benefits the twin with the smaller placental part. Type III sFGR placentas exhibited the highest AV ratio, resulting in the lowest BWR/PR.

DISCUSSION

A larger shared circulation mitigates the impact of an unequally divided placenta on fetal growth. This effect surpasses the influence of AA and VV diameters and is most prominent in Type III sFGR placentas.

Association between fetal growth-restriction and retinopathy of prematurity using a unique identical twin model

BACKGROUND

Research in singletons identified fetal growth restriction (FGR) as a risk factor for retinopathy of prematurity (ROP), but is generally subject to confounding by genetic, obstetric, and maternal factors. We investigated the effect of FGR on ROP in growth-discordant identical twins, thereby controlling for confounding factors.

METHODS

All data of monochorionic (MC) twin pairs with a birth weight discordance ≥20% born in our center between 2010 and 2021 were retrospectively reviewed for the presence of ROP. Potential risk factors for ROP were analyzed. Outcomes were compared between the smaller and larger twin.

RESULTS

We included 88 MC twin pairs with growth discordance. In 34% (30/88), both neonates were at risk of ROP. Prevalence of ROP was higher among the smaller twin compared to the larger twin, 30% (9/30) versus 13% (4/30), respectively (OR 2.8, 95% CI: 1.2-6.6). The smaller twin had a longer duration of mechanical ventilation (8 (1-20) versus 2 (1-4) days) and received their first red blood cell transfusion at an earlier postmenstrual age (29.6 (28.1-31.6) versus 30.4 (29.7-32.6) weeks).

CONCLUSIONS

In this identical twin model, FGR is associated with almost tripled odds of ROP development, suggesting that both unfavorable antenatal growth conditions and adverse neonatal outcomes affect postnatal retinal vascular proliferation.

IMPACT

Fetal growth restriction in growth-discordant identical twins is associated with almost tripled odds of developing retinopathy of prematurity in the smaller twin. Since these twins do not only differ in birth weight but also duration of mechanical ventilation and timing of the first red blood cell transfusion, both unfavorable antenatal growth conditions and adverse neonatal outcomes can affect postnatal retinal vascular proliferation. More attention for preventing retinopathy of prematurity is needed in those with fetal growth restriction who received prolonged duration of mechanical ventilation, oxygen supplementation, or a first red blood cell transfusion <32 weeks postmenstrual age.

Outcome of laser photocoagulation in monochorionic diamniotic twin pregnancy complicated by Type-II selective fetal growth restriction

OBJECTIVES

To evaluate the outcome of monochorionic diamniotic (MCDA) twins complicated by Type-II selective fetal growth restriction (sFGR) who underwent fetoscopic laser photocoagulation and to validate a previously proposed subclassification system for Type-II sFGR in a large multicenter cohort.

METHODS

This retrospective multicenter cohort study included all MCDA twins complicated by Type-II sFGR who underwent laser photocoagulation of placental anastomoses at four large tertiary fetal-care centers between 2006 and 2020. Cases were subclassified according to a recently proposed system based on Doppler evaluation of the ductus venosus (DV) and middle cerebral artery (MCA) into Type-IIA (normal DV flow and MCA peak systolic velocity (PSV) of the growth-restricted fetus) or Type-IIB (absent or reversed flow in the DV during atrial contraction and/or MCA-PSV ≥ 1.5 multiples of the median of the growth-restricted fetus). Demographic characteristics and pregnancy outcomes were compared between the groups. Data are presented as mean ± SD or n (%) as appropriate. P-values < 0.05 were considered statistically significant.

RESULTS

A total of 98 patients with MCDA twins met our inclusion criteria, with 56 subclassified as Type IIA and 42 as Type IIB. Demographic characteristics were similar between the groups; however, Type-IIB cases had a significantly earlier gestational age at diagnosis and at laser surgery, as well as larger intertwin estimated fetal weight discordance, which may be a reflection of disease severity. Postnatal survival of the growth-restricted fetus to 30 days of age was significantly lower in Type-IIB compared to Type-IIA cases (23.8% vs 46.4%; P = 0.034).

CONCLUSIONS

In MCDA twins complicated by Type-II sFGR and treated with laser photocoagulation of placental anastomoses, preoperative Doppler assessment of the DV and MCA helped identify a subset of patients at increased risk of demise of the growth-restricted fetus following intervention. This study provides valuable information for guiding surgical management and patient counseling. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Directive clinique no 440 : Prise en charge de la grossesse gémellaire monochoriale

OBJECTIF

Cette directive clinique passe en revue les données probantes sur la prise en charge de la grossesse gémellaire monochoriale normale et compliquée.

POPULATION CIBLE

Les femmes menant une grossesse gémellaire ou multiple de haut rang. BéNéFICES, RISQUES ET COûTS: L'application des recommandations de cette directive devrait améliorer la prise en charge des grossesses gémellaires (ou multiples de haut rang) monochoriales compliquées et non compliquées. Ces recommandations aideront les fournisseurs de soins à surveiller adéquatement les grossesses gémellaires monochoriales ainsi qu'à détecter et prendre en charge rapidement les complications associées de façon optimale afin de réduire les risques de morbidité et mortalité périnatales. Ces recommandations impliquent une surveillance échographique plus fréquente en cas de grossesse monochoriale qu'en cas de grossesse bichoriale. DONNéES PROBANTES: La littérature publiée a été colligée par des recherches dans les bases de données PubMed et Cochrane Library au moyen de termes MeSH pertinents (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Les résultats ont été restreints aux revues systématiques, aux essais cliniques randomisés et aux études observationnelles. Aucune date limite n'a été appliquée, mais les résultats ont été limités aux contenus en anglais ou en français. MéTHODES DE VALIDATION: Les auteurs principaux ont rédigé le contenu et les recommandations et ils se sont entendus sur ces derniers. Le conseil d'administration de la SOGC a approuvé la version définitive aux fins de publication. Les auteurs ont évalué la qualité des données probantes et la force des recommandations en utilisant le cadre méthodologique GRADE (Grading of Recommendations Assessment, Development and Evaluation). Voir l'annexe A en ligne (tableau A1 pour les définitions et tableau A2 pour l'interprétation des recommandations fortes et conditionnelles [faibles]). PROFESSIONNELS CONCERNéS: Spécialistes en médecine fœto-maternelle, obstétriciens, radiologues, échographistes, médecins de famille, infirmières, sages-femmes, résidents et autres fournisseurs de soins de santé qui s'occupent de femmes menant une grossesse gémellaire ou multiple de haut rang. RéSUMé POUR TWITTER: Directive canadienne (SOGC) pour le diagnostic, la surveillance échographique et la prise en charge des complications de la grossesse gémellaire monochoriale (p. ex., STT, TAPS, retard de croissance sélectif, cojumeau acardiaque, monoamnionicité et mort d'un jumeau). DÉCLARATIONS SOMMAIRES: RECOMMANDATIONS.

Guideline No. 440: Management of Monochorionic Twin Pregnancies

OBJECTIVE

This guideline reviews the evidence-based management of normal and complicated monochorionic twin pregnancies.

TARGET POPULATION

Women with monochorionic twin or higher order multiple pregnancies.

BENEFITS, HARMS, AND COSTS

Implementation of these recommendations should improve the management of both complicated and uncomplicated monochorionic (and higher order multiple) twin pregnancies. They will help users monitor monochorionic twin pregnancies appropriately and identify and manage monochorionic twin complications optimally in a timely manner, thereby reducing perinatal morbidity and mortality. These recommendations entail more frequent ultrasound monitoring of monochorionic twins compared to dichorionic twins.

EVIDENCE

Published literature was retrieved through searches of PubMed and the Cochrane Library using appropriate MeSH headings (Twins, Monozygotic; Ultrasonography, Prenatal; Placenta; Fetofetal Transfusion; Fetal Death; Fetal Growth Retardation). Results were restricted to systematic reviews, randomized controlled clinical trials, and observational studies. There were no date limits, but results were limited to English or French language materials.

VALIDATION METHODS

The content and recommendations were drafted and agreed upon by the principal authors. The Board of the SOGC approved the final draft for publication. The authors rated the quality of evidence and strength of recommendations using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. See online Appendix A (Tables A1 for definitions and A2 for interpretations of strong and conditional [weak] recommendations).

INTENDED AUDIENCE

Maternal-fetal medicine specialists, obstetricians, radiologists, sonographers, family physicians, nurses, midwives, residents, and other health care providers who care for women with monochorionic twin or higher order multiple pregnancies.

TWEETABLE ABSTRACT

Canadian (SOGC) guidelines for the diagnosis, ultrasound surveillance and management of monochorionic twin pregnancy complications, including TTTS, TAPS, sFGR (sIUGR), acardiac (TRAP), monoamniotic twins and intrauterine death of one MC twin.

SUMMARY STATEMENTS

RECOMMENDATIONS.

Comparison of New Bronchopulmonary Dysplasia Definitions on Long-Term Outcomes in Preterm Infants

OBJECTIVE

To compare the discriminative performances of the 2018 National Institutes of Health (NIH) and the 2019 Jensen definitions of bronchopulmonary dysplasia (BPD) with the 2001 NIH definition on adverse neurodevelopmental and respiratory outcomes at 2 years and 5 years corrected age.

STUDY DESIGN

In this single-center retrospective cohort study, outcomes of infants born at <30 weeks of gestational age were collected. The 3 definitions of BPD were compared by adding the different definitions to the National Institute of Child Health and Human Development's outcome prediction model for neurodevelopmental impairment (NDI) or death. Discriminative performance was compared for both outcomes at 2 years and 5 years corrected age by calculating the areas under the receiver operating characteristic curve and z-statistics.

RESULTS

The presence of BPD and its severity were determined in 584 infants. There were considerable shifts in BPD grading among the different definitions. At both time points, all BPD definition models had comparable discriminating power for NDI and respiratory morbidity, with one exception. Compared with the 2001 NIH definition, the 2018 NIH definition had less predictive power for the neurologic outcome at 2 years corrected age.

CONCLUSIONS

Our comparison of the 3 BPD definitions shows similar discriminative performance on long term neurodevelopmental and respiratory outcomes at 2 years and 5 years corrected age.

Natural evolution and risk factors for adverse outcome in selective intrauterine growth restriction under expectant management: A retrospective observational study

OBJECTIVE

To evaluate the natural evolution of and risk factors for the adverse outcome of monochorionic twins with selective intrauterine growth restriction (sIUGR) under expectant management.

METHODS

Retrospective study conducted in a single tertiary referral center. The clinical characteristics and neonatal outcomes of 153 patients with sIUGR under expectant management were evaluated, and the risk factors leading to adverse outcomes were explored.

RESULTS

Fifty-one patients (33.3%) showed a changed pattern in umbilical artery Doppler at the last examination, occurring in all types of sIUGR. Compared with type Ia, the gestational age of diagnosis was earlier, the estimated fetal body weight difference at diagnosis was greater, and the rate of severe neonatal complications in both fetuses was significantly higher in type Ib (P < 0.05). Univariate and multivariate logistic regression analyses showed that type II (odds ratio [OR] 5.41, 95% confidence interval [CI] 2.34-12.51; P < 0.001) and type III (OR 9.11, 95% CI 3.02-27.50; P < 0.001) were associated with adverse perinatal outcomes in sIUGR.

CONCLUSION

Type II and III sIUGR are independent risk factors predicting adverse outcomes of sIUGR. Different types of sIUGR could convert to each other. The outcome of type Ib is poorer than that of type Ia.

Twin Anemia-Polycythemia Sequence (TAPS): From Basic Research to Clinical Practice

Twin pregnancy is associated with an increased risk of perinatal and maternal complications, and early establishment of the chorionicity type defines this risk. In monochorionic (MC) pregnancies, the fetuses share the same placental mass and exhibit vascular anastomoses crossing the intertwin membrane, and the combination and pattern of anastomoses determine the primary clinical picture and occurrence of future complications. Twin Anemia-Polycythemia Sequence (TAPS) was first described in 2006 after fetoscopic laser surgery in twin-to-twin transfusion syndrome (TTTS) twins, and in 2007, the first spontaneous cases were reported, recognizing TAPS as an individualized vascular identity in fetofetal transfusion syndromes. There are two types of TAPS: spontaneous (3-5%) and iatrogenic or postlaser (2-16%). TAPS consists of small diameter arteriovenous anastomoses (<1 mm) and low-rate, small-caliber AA anastomoses in the absence of amniotic fluid discordances. There are certain antenatal and postnatal diagnostic criteria, which have progressively evolved over time. New, additional secondary markers have been proposed, and their reliability is being studied. The best screening protocol for TAPS in MC twins is still a matter of debate. This review provides a survey of the relevant literature on the epidemiology, vascular pathophysiology, underlying hemodynamic factors that regulate mismatched vascular connections, and diagnostic criteria of this condition. The aim is to increase awareness and knowledge about this recently identified and frequently unrecognized and misdiagnosed pathology.

The Value of Delta Middle Cerebral Artery Peak Systolic Velocity for the Prediction of Twin Anemia-Polycythemia Sequence-Analysis of a Heterogenous Cohort of Monochorionic Twins

Introduction: Twin anemia-polycythemia sequence (TAPS) is a complication in monochorionic-diamniotic (MCDA) twin pregnancies. This study analyzes whether the prenatal diagnosis using delta middle cerebral artery-peak systolic velocity (MCA-PSV) > 0.5 multiples of the median (MoM) (delta group) detects more TAPS cases than the guideline-based diagnosis using the MCA-PSV cut off levels of >1.5 and <1.0 MoM (cut-off group), in a heterogenous group of MCDA twins. Methods: A retrospective analysis of 348 live-born MCDA twin pregnancies from 2010 to 2021 with available information on MCA-PSV within one week before delivery and hemoglobin-values within 24 h postnatally were considered eligible. Results: Among postnatal confirmed twin pairs with TAPS, the cut-off group showed lower sensitivity than the delta group (33% vs. 82%). Specificity proved higher in the cut-off group with 97% than in the delta group at 86%. The risk that a TAPS is mistakenly not recognized prenatally is higher in the cut-off group than in the delta group (52% vs. 18%). Conclusions: Our data shows that delta MCA-PSV > 0.5 MoM detects more cases of TAPS, which would not have been diagnosed prenatally according to the current guidelines. In the collective examined in the present study, TAPS diagnostics using delta MCA-PSV proved to be a more robust method.

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

INTRODUCTION

No 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.

METHODS

This 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.

RESULTS

Of 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).

DISCUSSION

No 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.

Establishment of a no-notice drill mode evaluation system for public health emergencies

OBJECTIVE

At present, there are some no-notice drill mode evaluation systems for public health emergencies in Chinese hospitals, which are the subjects of assessment in this study. However, there is a lack of CDC. This study builds a set of no-notice drill mode evaluation systems for public health emergencies that involve the CDC.

METHODS

The indexes for these systems were based on the performance of two no-notice drills for public health emergencies in Guangdong Province. Twenty experts were invited to screen the indicators during two rounds of the Delphi method to determine the weight of first- and second-level indexes through the analytic hierarchy process, and the weight of the third-level index was calculated using the percentage method.

RESULTS

After two rounds of expert consultation, we obtained four first-level indicators, twenty-six second-level indicators and eighty-six third-level indicators. According to the weight calculated by analytic hierarchy process, the weights of the first-level indicators are emergency preparation (0.2775), verification and consultation regarding an epidemic situation (0.165), field investigation and control (0.3925) and summary report (0.165). Sensitivity analysis shows that the stability of the index is good.

CONCLUSION

The no-notice drill mode evaluation system for public health emergencies constructed in this study can be applied to public health departments such as the CDC. Through promotion, it can provide a scientific basis for epidemiological investigation assessment.

Pathophysiology, diagnosis, and management of twin anemia polycythemia sequence in monochorionic multiple gestations

Twin anemia polycythemia sequence (TAPS) is a consequence of unequal sharing of red blood cells between monochorionic twins resulting in anemia in the donor and polycythemia in the recipient twin. Prenatally TAPS can occur spontaneously or complicate incomplete laser surgery for twin transfusion syndrome. While there may be clinical overlap with twin transfusion syndrome or selective fetal growth restriction, diagnosis relies on Doppler measurement of middle cerebral artery peak systolic velocities. Significantly discordant velocities are diagnostic, while severity staging is based on signs of cardiovascular compromise. Conservative management, fetoscopic laser coagulation, selective twin reduction, fetal blood and exchange transfusion, and delivery may be selected guided by the gestational age of diagnosis, the severity of the condition, the likelihood of success, and the patients' priorities. Prenatal curative treatment that minimizes the risk for prematurity and residual morbidity at birth is most likely to offer the greatest short-term and long-term benefits.

What fetal medicine specialists should know about the monochorionic placenta

Monochorionic twins are at risk of transfusion imbalances as long as they are connected to the shared placenta during their intrauterine journey. This review article addresses the macroscopic examination of the monochorionic placenta at the time of birth and explains placental dye injection studies to document the vascular anastomoses and placental sharing. We elaborate on the different types of anastomoses, the importance of how the placenta is divided between the twins, and the angioarchitecture in twin-twin transfusion syndrome, twin anemia polycythemia sequence and selective fetal growth restriction.

Comparison of pregnancy outcomes and placental characteristics between selective fetal growth restriction with and without thick arterio-arterial anastomosis in monochorionic diamniotic twins

Background

Unequal placental territory in monochorionic diamniotic twins is a primary cause of selective fetal growth restriction (sFGR), and vascular anastomoses play important role in determining sFGR prognosis. This study investigated differences in placental characteristics and pregnancy outcomes in cases of sFGR with and without thick arterio-arterial anastomosis (AAA).

Methods

A total of 253 patients diagnosed with sFGR between April 2013 and April 2020 were retrospectively analyzed. An AAA greater than 2 mm in diameter was defined as a thick AAA. We compared placental characteristics and pregnancy outcomes between cases of sFGR with and without thick AAA.

Results

Prevalence of AAA, thick arterio-venous anastomosis (AVA), veno-venous anastomosis (VVA), and thick VVA were significantly higher in the thick AAA group relative to the non-thick AAA group (100.0 vs. 78.5%, P < 0.001; 44.3 vs. 15.4%, P < 0.001; 27.1 vs. 10.8%, P = 0.017, and 24.3 vs. 6.2%, P = 0.004, respectively). The total numbers of AVA and total anastomoses were significantly higher in thick AAA group relative to the non-thick AAA group (5 [1, 14] vs. 3 [1, 15, P = 0.016; and 6 [1, 15] vs. 5 [1, 16], P = 0.022, respectively). The total diameter of AAA, AVA, VVA, and all anastomoses in the thick AAA group was larger than in the non-thick AAA group (3.4 [2.0,7.1] vs. 1.4 [0.0, 3.3], P < 0.001; 6.3 [0.3, 12.0] vs. 2.5 [0.3, 17.8], P < 0.001; 4.2±1.8 vs. 1.9±1.2, P =0.004; and 10.7 [3.2,22.4] vs. 4.4 [0.5, 19.3], P < 0.001, respectively). Growth-restricted fetuses in the thick AAA group exhibited significantly increased birthweight relative to those in thenon-thick AAA group (1570 (530, 2460)g vs. 1230 (610, 2480)g, p = 0.002).

Conclusions

In the placentas associated with sFGR, thick AAA can co-occur with thick AVA and VVA, and placental angiogenesis may differ significantly based upon whether or not thick AAA is present. The birth weights of growth-restricted fetuses in cases of sFGR with thick AAA are larger than in cases without thick AAA.

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

INTRODUCTION

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.

METHODS

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.

RESULTS

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.

DISCUSSION

VV anastomoses are associated with a decreased birth weight discordance relative to the placental sharing discordance, independent of the AA anastomoses.

Perinatal outcome of pregnancy complicated by twin anemia-polycythemia sequence: systematic review and meta-analysis

OBJECTIVE

To report the perinatal outcome of monochorionic diamniotic (MCDA) twin pregnancies complicated by twin anemia-polycythemia sequence (TAPS), according to the type of TAPS (spontaneous or postlaser) and the management option adopted.

METHODS

MEDLINE, EMBASE and The Cochrane Library databases were searched for studies reporting on the outcome of twin pregnancies complicated by TAPS. Inclusion criteria were non-anomalous MCDA twin pregnancies with a diagnosis of TAPS. The primary outcome was perinatal mortality; secondary outcomes were neonatal morbidity and preterm birth (PTB). The outcomes were stratified according to the type of TAPS (spontaneous or following laser treatment for twin-twin transfusion syndrome) and the management option adopted (expectant, laser surgery, intrauterine transfusion (IUT) or selective reduction (SR)). Random-effects meta-analysis of proportions was used to analyze the data.

RESULTS

Perinatal outcome was assessed according to whether TAPS occurred spontaneously or after laser treatment in 506 pregnancies (38 studies). Intrauterine death (IUD) occurred in 5.2% (95% CI, 3.6-7.1%) of twins with spontaneous TAPS and in 10.2% (95% CI, 7.4-13.3%) of those with postlaser TAPS, while the corresponding rates of neonatal death were 4.0% (95% CI, 2.6-5.7%) and 9.2% (95% CI, 6.6-12.3%), respectively. Severe neonatal morbidity occurred in 29.3% (95% CI, 25.6-33.1%) of twins after spontaneous TAPS and in 33.3% (95% CI, 17.4-51.8%) after postlaser TAPS, while the corresponding rates of severe neurological morbidity were 4.0% (95% CI, 3.5-5.7%) and 11.1% (95% CI, 6.2-17.2%), respectively. PTB complicated 86.3% (95% CI, 77.2-93.3%) of pregnancies with spontaneous TAPS and all cases with postlaser TAPS (100% (95% CI, 84.3-100%)). Iatrogenic PTB was more frequent than spontaneous PTB in both groups. Perinatal outcome was assessed according to the management option adopted in 417 pregnancies (21 studies). IUD occurred in 9.8% (95% CI, 4.3-17.1%) of twins managed expectantly and in 13.1% (95% CI, 9.2-17.6%), 12.1% (95% CI, 7.7-17.3%) and 7.6% (95% CI, 1.3-18.5%) of those treated with laser surgery, IUT and SR, respectively. Severe neonatal morbidity affected 27.3% (95% CI, 13.6-43.6%) of twins in the expectant-management group, 28.7% (95% CI, 22.7-35.1%) of those in the laser-surgery group, 38.2% (95% CI, 18.3-60.5%) of those in the IUT group and 23.3% (95% CI, 10.5-39.2%) of those in the SR group. PTB complicated 80.4% (95% CI, 59.8-94.8%), 73.4% (95% CI, 48.1-92.3%), 100% (95% CI, 76.5-100%) and 100% (95% CI, 39.8-100%) of pregnancies after expectant management, laser surgery, IUT and SR, respectively.

CONCLUSIONS

The present meta-analysis provides pooled estimates of the risks of perinatal mortality, neonatal morbidity and PTB in twin pregnancies complicated by TAPS, stratified by the type of TAPS and the management option adopted. Although a direct comparison could not be performed, the results from this systematic review suggest that spontaneous TAPS may have a better prognosis than postlaser TAPS. No differences in terms of mortality and morbidity were observed when comparing different management options for TAPS, although these findings should be interpreted with caution in view of the limitations of the included studies. Individualized prenatal management, taking into account the severity of TAPS and gestational age, is currently the recommended strategy. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Monochorionic diamniotic twin pregnancies

About one in five twin pregnancies are monochorionic diamniotic. In these twins, transfusion imbalances may develop due to the invariably present vascular anastomoses. The most severe imbalance is twin-twin transfusion syndrome, which presents as a significant amniotic fluid difference diagnosed on ultrasound scan, usually before 26 weeks. Another transfusion imbalance is twin anemia polycythemia sequence, a severe hemoglobin difference occurring mainly after 26 weeks in previously uncomplicated pregnancies. Fetoscopic laser coagulation of the anastomoses addresses the cause of these transfusion imbalances. Besides transfusion imbalances, the monochorionic placenta may be unevenly divided, or one part may be dysfunctional, leading to an intertwin growth difference of more than 20%. Here, laser ablation of the anastomoses will usually not cure the problem but aims to protect the appropriately growing twin if the growth-restricted co-twin dies. In monochorionic twins, structural anomalies are twice as common as in singleton pregnancies, probably due to a teratogenic effect of the embryonic splitting or because of transfusion imbalances. In contrast, chromosomal anomalies appear less common, possibly because they more likely result in an early demise. Selective reduction is feasible in monochorionic pregnancies but carries increased risks of loss, miscarriage, and early birth than a selective reduction in a dichorionic setting. Finally, if one monochorionic twin dies spontaneously, its co-twin may acutely exsanguinate into the demised co-twin, which may result in the loss of both twins or brain damage in the surviving twin. This update addresses the pathophysiology, diagnosis, and management of these common complications in monochorionic diamniotic twin pregnancies.

Screening, Management and Delivery in Twin Pregnancy

The following AWMF guideline (DGGG/AGG & DEGUM responsible) deals with the diagnosis, screening and management of twins as well as the timing and mode of birth.Twin pregnancies can be classified as dichorionic diamniotic (DC DA), monochorionic diamniotic (MC DA) and monochorionic monoamniotic (MC MA) which are always monochorionic.Twin pregnancies can be concordant (both twins are affected) or discordant (only one twin is affected) for chromosomal defects, malformations, growth restriction and hemodynamic disorders.Chorionicity is the prognostically most significant parameter. Monochorial twins have significantly higher risks of intrauterine morbidity and mortality compared to dichorial twins.In particular, general aspects of twin pregnancies such as dating, determination of chorionicity and amnionicity, the labeling of twin fetuses and the perinatal switch phenomenon are discussed.Routine monitoring of MC and DC twin pregnancies with ultrasound at 11-13^+ 6 weeks of gestation for chromosomal defects, invasive prenatal diagnosis, first-trimester NT or CRL discrepancies, early diagnosis of fetal anatomical defects, and management of twins with abnormalities, including selective fetocide, is described.Second trimester screening and management for preterm birth, intrauterine selective growth restriction (sFGR), classification of monochorial twins with sFGR, and management of the surviving twin after the death of the co-twin are described.Complications exclusively affecting MC twins include Twin to Twin Transfusion Syndrome (TTTS) with the important topics screening, prognosis, complications of laser therapy, timing of delivery, risks for brain abnormalities and delayed neurological development, Twin Anemia-Polycythemia Sequence (TAPS) and Twin Reversed Arterial Perfusion (TRAP) Sequence. This also includes MC MA twins as well as conjoined twins.Finally, the birth mode and time for DC and MC twin pregnancies are described.The information is summarized in 62 recommendations for action, 4 tables and 8 illustrations with comprehensive background texts.The guideline is an international guideline adaptation (ISUOG, NICE) as well as a systematic literature search and is up-to-date.

Controversies in the management of twin pregnancy

Despite many advances in antenatal care, twin pregnancies still experience more adverse outcomes, in particular perinatal morbidity and mortality. They also pose a multitude of challenges and controversies, as outlined in this Review. Moreover, they are less likely to be included in clinical trials. Many issues on classification and management remain under debate. Efforts at standardizing diagnostic criteria, monitoring protocols, management and outcome reporting are likely to reduce their perinatal risks. The top 10 most important research uncertainties related to multiple pregnancies have been identified by both clinicians and patients. More robust research in the form of randomized trials and large well-conducted prospective cohort studies is needed to address these controversies. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Twin anemia polycythemia sequence in dichorionic diamniotic twins: A case report and review of the literature

Although rare, literature demonstrates evidence that vascular anastomoses do occur in dichorionic twins. Therefore, twin anemia polycythemia sequence should be considered as a differential diagnoses in dichorionic twins if there is suspicion on antenatal ultrasound.

Twin to twin transfusion syndrome

Twin to twin transfusion syndrome (TTTS) is a common complication that typically presents in the second trimester of pregnancy in 10-15% of monochorionic twins due to net transfer of volume and hormonal substances from one twin to the other across vascular anastomoses on the placenta. Without recognition and treatment, TTTS is the greatest contributor to fetal loss prior to viability in 90-100% of advanced cases. Ultrasound diagnosis of monochorionicity is most reliable in the first trimester and sets the monitoring strategy for this type of twins. The diagnosis of TTTS is made by ultrasound with the findings of polyhydramnios due to volume overload and polyuria in one twin and oligohydramnios due to oliguria of the co-twin. Assessment of bladder filling as well as arterial and venous Doppler patterns are required for staging disease severity. Assessment of fetal cardiac function also provides additional insight into the fetal cardiovascular impacts of the disease as well as help identify fetuses that may require postnatal follow up. Fetoscopic laser ablation of the communicating vascular anastomoses between the twins is the standard treatment for TTTS. It aims to cure the condition by interrupting the link between their circulations and making them independent of one another. Contemporary outcome data after laser surgery suggests survival for both fetuses can be anticipated in up to 65% of cases and survival of a single fetus in up to 88% of cases. However, preterm birth remains a significant contributor to postnatal morbidity and mortality. Long term outcomes of TTTS survivors indicate that up to 11% of children may show signs of neurologic impairment. Strategies to minimize preterm birth after treatment and standardized reporting by laser centers are important considerations to improve overall outcomes and understand the long-term impacts of TTTS.

Respiratory distress syndrome and bronchopulmonary dysplasia after fetal growth restriction: Lessons from a natural experiment in identical twins

BACKGROUND

Fetal growth restriction (FGR) is thought to negatively affect lung development resulting in increased respiratory morbidity. However, research performed in singletons is often limited by a certain level of bias caused by individual differences in genetic constitution, obstetrical and maternal factors.

METHODS

Respiratory morbidity was compared between the smaller and the larger twin in monochorionic twins with selective fetal growth restriction (sFGR), defined as a birth weight discordance ≥ 20%, born in our center between 2010 and 2019 in this retrospective study. Respiratory distress syndrome (RDS) was diagnosed based on the clinical picture of a neonate with respiratory failure requiring mechanical ventilation and/or surfactant, confirmed by a chest X-ray. Bronchopulmonary dysplasia (BPD) was diagnosed when the neonate required treatment with >21% oxygen for at least 28 days.

FINDINGS

Median gestational age at birth for the 94 included pregnancies was 32.4 (IQR 30.4-34.3) weeks. Within-pair analyses showed that the prevalence of RDS was lower in the smaller twin compared to the larger twin, 19.1% (18/94) vs 34.0% (32/94), respectively (p = 0.004). The odds of RDS for the larger twin was doubled (OR 2.1 (CI95% 1.3-3.5). In contrast, the rate of BPD in the smaller twin was higher as opposed to the larger twin, 16.7% (15/90) vs 6.7% (6/89), respectively (p = 0.008), with a more than doubled odds (OR 2.5 (CI95% 1.3-4.9)).

INTERPRETATION

Despite being genetically identical, sFGR twins have different respiratory outcomes. Adverse growth condition in utero in the smaller twin is associated with a reduced odds of RDS at birth but a more than doubled odds of BPD, reflecting the pathophysiologic adverse effect of growth restriction on lung development.

FUNDING

The Dutch Heart Foundation (2017T075).

Reduction in twin stillbirth following implementation of NICE guidance

OBJECTIVE

There has been an unprecedented fall in the rate of stillbirth in twin pregnancy in the UK. It is contested whether implementation of the National Institute for Health and Care Excellence (NICE) guidance on the antenatal management of uncomplicated twin pregnancies has contributed to this change. The aim of this study was to investigate whether the implementation of NICE guidance was associated with a reduction in the rate of stillbirth in twin pregnancies delivered in a large UK hospital.

METHODS

This was a retrospective cohort study including all twin pregnancies delivered at St George's Hospital, London, UK, between 2000 and 2018. Data were analyzed according to two time periods: before implementation of the NICE guidance on twins (before June 2013; pre-NICE) and after its implementation (after June 2013; post-NICE). The exclusion criteria were higher-order multiple gestations, pregnancies of unknown chorionicity, pregnancies complicated by miscarriage, those that underwent termination and those diagnosed with vanishing twin. The main outcome was stillbirth. Other outcomes included neonatal death (NND), admission to the neonatal intensive care unit (NICU) and emergency Cesarean section. We planned a priori a sensitivity analysis according to chorionicity. The chi-square test and Mann-Whitney U-test were used to compare outcomes between the study groups.

RESULTS

We included in the analysis 1666 twin pregnancies (3332 fetuses), of which 1114 pregnancies (2228 fetuses) were delivered before and 552 pregnancies (1104 fetuses) after June 2013. Of those, 1299 were dichorionic and 354 were monochorionic diamniotic. The incidence of stillbirth was significantly lower in the post-NICE than in the pre-NICE group (3.6 per 1000 births vs 13.5 per 1000 births; P = 0.008). The reduction in stillbirth rate was from 8.5 to 3.6 per 1000 births (P = 0.161) in dichorionic and from 33.6 to 3.8 per 1000 births (P = 0.011) in monochorionic diamniotic twin pregnancies. There was no significant difference in the rates of NND (P = 0.625), NICU admission (P = 0.506) or emergency Cesarean section (P = 0.820) between the two groups. The median gestational age at delivery was significantly lower in the post-NICE than in the pre-NICE group (median 36.3 vs 36.9 weeks; P < 0.001), as a consequence of a significant increase in preterm birth between 34 and 37 weeks' gestation (39.3% vs 27.0%; P = 0.002), but not before 34 weeks (P = 0.473).

CONCLUSIONS

A significant reduction of > 70% in the stillbirth rate in twin pregnancies was noted after implementation of the NICE guidance. This reduction was statistically significant in monochorionic, but not dichorionic, twin pregnancies. The improvement in twin pregnancy outcome was achieved without a concomitant increase in NND, admission to the NICU or emergency Cesarean section. © 2020 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Performance of Antenatal Diagnostic Criteria of Twin-Anemia-Polycythemia Sequence

This study aims to elicit the validation performance of different diagnostic criteria and to evaluate the disease course and perinatal outcomes of pregnancies complicated by twin anemia polycythemia sequence (TAPS). Monochorionic diamniotic (MCDA) twin pregnancies who received serial middle cerebral artery (MCA) peak systolic velocity (PSV) measurements without non-TAPS-related demise or major anomalies were included. Course of disease, antenatal intervention, additional ultrasound features, and perinatal outcomes were compared between each criteria and onset. Forty-nine cases of TAPS and 203 non-TAPS controls were identified. The incidence of TAPS was 19.2%, 15.7%, 7.8%, and 6.3% for ΔPSV MoM > 0.373, ΔPSV MoM > 0.5, traditional, and Delphi consensus criteria, respectively (p < 0.001). The incidence of antenatal intervention was 55.1, 62.5, 75.0, and 87.5%, respectively. Furthermore, cases detected according to the Delphi consensus criteria had a higher rate of progression or intervention compared to cases detected with ΔPSV MoM > 0.373 (87.0 vs. 59.0%, p = 0.037). TAPS had a significantly higher birth weight discordance than uncomplicated MCDA twins (25.3 vs. 7.3%, p < 0.001). Application of four different diagnostic criteria for TAPS leads to significant differences in the incidence, severity, and antenatal intervention. The Delphi criteria identified more severe cases likely to require intervention, and the delta PSV > 0.373 criteria identified milder cases, without a significant impact on neonatal outcomes.

Middle Cerebral Artery Doppler Velocimetry for the Diagnosis of Twin Anemia Polycythemia Sequence: A Systematic Review

Twin anemia polycythemia sequence (TAPS) is a rare complication of monochorionic diamniotic (MCDA) twins. Middle cerebral artery peak systolic velocity (MCA-PSV) measurements are used to screen for TAPS while fetal or neonatal hemoglobin levels are required for definitive diagnosis. We sought to perform a systematic review of the efficacy of MCA-PSV in diagnosing TAPS. Search criteria were developed using relevant terms to query the Pubmed, Embase, and SCOPUS electronic databases. Publications reporting diagnostic characteristics of MCA-PSV measurements (i.e., sensitivity, specificity or receiver operator curves) were included. Each article was assessed for bias using the Quality Assessment of Diagnostic Accuracy Studies II (QUADAS II) tool. Results were assessed for uniformity to determine whether meta-analysis was feasible. Data were presented in tabular form. Among publications, five met the inclusion criteria. QUADAS II analysis revealed that four of the publications were highly likely to have bias in multiple areas. Meta-analysis was precluded by non-uniformity between definitions of TAPS by MCA-PSV and neonatal or fetal hemoglobin levels. High-quality prospective studies with consistent definitions and ultrasound surveillance protocols are still required to determine the efficacy of MCA-PSV in diagnosing TAPS. Other ultrasound findings (e.g., placenta echogenicity discordance) may augment Doppler studies.