The North American Fetal Therapy Network Consensus Statement: Management of Complicated Monochorionic Gestations

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).

Patient Experience and Decision-Making Process for Laser Photocoagulation for Monochorionic Twin Pregnancy: A Qualitative Exploration

INTRODUCTION

The aim of the study was to explore patients' perspectives on diagnosis and treatment options for complicated monochorionic multiple gestations, and experiences with fetoscopic laser photocoagulation.

METHODS

This is a prospective cohort study of patients undergoing laser photocoagulation. Participants were interviewed during pregnancy and the postpartum period. Qualitative analysis was performed.

RESULT

Twenty-seven patients who were candidates for laser photocoagulation were included. All elected to have laser photocoagulation. Patients chose surgery with goals of improving survival, decreasing the risk of preterm delivery, and improving the long-term health of their fetuses. They demonstrated accurate knowledge of the risks and benefits of treatment. Most (74%) felt that laser photocoagulation represented their only viable clinical option. Few seriously considered pregnancy termination or selective reduction (7% and 11% respectively). Postpartum, patients expressed no regrets about their decisions for surgery, but many felt unprepared for the challenges of preterm delivery.

CONCLUSION

Participants weighed treatment options similarly to fetal specialists. They acknowledged but did not seriously consider treatments other than fetoscopic laser photocoagulation and were highly motivated to do whatever they could to improve outcomes for their fetuses.

Introducing a New Predictor of Chorionicity in the Second and Third Trimesters: The “Cleft Sign”

Objective:

The aim of this study was to suggest a new sonographic sign, which could be helpful in the determination of chorionicity in twin pregnancies, during the second and third trimesters.

Materials and Methods:

This was a retrospective study evaluating the sonographic images of 50 women with twin pregnancy. Out of 50 twin pregnancy case reviewed, only 27 were included. Those patient cases that were included were scanned by a single radiologist. The presence of a hypoechoic cleft, in the thickness of placental bulk, could be detected in all of the dichorionic pregnancy cases. This sonographic appearance was referred to as the “cleft sign.”

Results:

The “cleft sign” was present in all the dichorionic diamniotic (DC-DA) twin pregnancy cases, but no similar appearance was seen in the monochorionic diamniotic (MC-DA) twins. Considering this sign, the radiologist was able to correctly diagnose the chorionicity of all 24 patients in the second and third trimester.

Conclusion:

The findings of the present study suggest a possible role for this newly identified “cleft sign.” This sonographic appearance is a hypoechoic cleft in the thickness of placenta, of dichorionic pregnancies, as an indicator of DC twin pregnancy. In this retrospective case analysis, the “cleft sign” was diagnostically significant in the second and third trimesters.

Mode of delivery, perinatal outcome and neurodevelopment in uncomplicated monochorionic diamniotic twins: a single-center retrospective cohort study

BACKGROUND

There is no agreement on the effect of planned mode of delivery in the perinatal morbidity and neurodevelopment in uncomplicated monochorionic diamniotic as well as regarding the safest mode of delivery. In this paper we have aimed to analyze the impact of the mode of delivery in uncomplicated monochorionic diamniotic twins ≥ 32 weeks of gestation.

MATERIAL AND METHODS

This study included 72 women, followed and attended at our department, with uncomplicated monochorionic diamniotic pregnancies who had a birth between 32.0 and 37.6 weeks of gestation from January 2012 to December 2018. Outcomes were recorded in women who underwent planned vaginal delivery (induced or spontaneous onset of labor), and women who underwent a planned cesarean section for any reason that excluded vaginal delivery. Primary outcomes included: (1) A composite of any of the following: neonatal death, 5-min Apgar score < 4, respiratory distress syndrome, bronchopulmonary dysplasia, sepsis, periventricular leukomalacia, intraventricular hemorrhage, and necrotizing enterocolitis. (2) Neurodevelopmental status at 2 years of corrected age.

RESULTS

In this period, 42 women (58.3%) had a planned vaginal delivery, and 30 women (41.7%) had a planned cesarean section. In the first group, 64.3% had a vaginal delivery. The rate of successful vaginal delivery was similar regardless the onset of labor. We did not find a higher composite perinatal morbidity in the planned vaginal delivery group (planned vaginal delivery: 3.6% vs. planned cesarean section: 8.3%, aOR 1.36, 95% CI 0.24-7.81). Considering the onset of labor, it was more frequent in the spontaneous subgroup (8.3% vs. 0%). The rate of neurodevelopmental impairment was higher in the planned cesarean section group, without reaching statistical significance [10.2% vs. 4.9%, aOR 1.53 (95% CI 0.37-6.29)].

CONCLUSIONS

In uncomplicated monochorionic diamniotic twins at ≥ 32 weeks of gestation, when the first twin is in vertex presentation, our results suggest that planned vaginal delivery is safe, with a successful outcome as well as high vaginal delivery rate.

Management of Complicated Monochorionic Twin Gestations: An Evidence-Based Protocol

Importance

Monochorionic (MC) twins are hemodynamically connected by vascular anastomoses within the single shared placenta. The transfer of fluid or blood from one fetus to the other may result in development of pathologic complications, such as twin-twin transfusion syndrome, twin anemia polycythemia sequence, selective intrauterine growth restriction, and twin reversed arterial perfusion sequence. Monoamniotic gestations, which comprise a small fraction of MC pregnancies, can also present with unique challenges, particularly antepartum umbilical cord entanglement. All these complications carry a high risk of fetal morbidity and mortality if not recognized and managed in a timely fashion.

Objective

The purpose of this article is to review evidence-based management of complicated MC twin gestations and propose a standardized approach to surveillance.

Evidence Acquisition

Monochorionic gestations account for the majority of complications that occur in twin pregnancies; however, there is unclear evidence on the appropriate surveillance for and management of specific complications associated with these pregnancies.

Results

This article summarizes management for each specific type of MC complication in a structured and clear manner.

Conclusions

Early pregnancy ultrasound, ideally between 10 and 13 weeks' gestation, is critical for the diagnosis and characterization of twin pregnancies. To improve outcomes for MC twins, appropriate fetal surveillance should be initiated at 16 weeks' gestation and continued until delivery.

Perinatal outcome after planned vaginal delivery in monochorionic compared with dichorionic twin pregnancy

OBJECTIVE

To assess, according to chorionicity, the perinatal outcome of twin pregnancy in which vaginal delivery is planned.

METHODS

JUMODA (JUmeaux MODe d'Accouchement) was a national prospective population-based cohort study of twin pregnancies, delivered in 176 maternity units in France, from February 2014 to March 2015. In this planned secondary analysis, we assessed, according to chorionicity, the perinatal outcome of twin pregnancies, in which vaginal delivery was planned, that delivered at or after 32 weeks of gestation with the first twin in cephalic presentation. In order to select a population with well-recognized indications for planned vaginal delivery, we applied the same exclusion criteria as those in the Twin Birth Study, an international randomized trial. Monochorionic twin pregnancies with twin-to-twin transfusion syndrome or twin anemia-polycythemia sequence were defined as complicated and were excluded. The primary outcome was a composite of intrapartum mortality and neonatal morbidity and mortality. Multivariable logistic regression models were used to control for potential confounders. Subgroup analyses were conducted according to birth order (first or second twin) and gestational age at delivery (< 37 or ≥ 37 weeks of gestation).

RESULTS

Among 3873 twin pregnancies, in which vaginal delivery was planned, that delivered at ≥ 32 weeks' gestation with the first twin in cephalic presentation, meeting the inclusion criteria of the Twin Birth Study, 729 (18.8%) were uncomplicated monochorionic twin pregnancies and 3144 (81.2%) were dichorionic twin pregnancies. The rate of composite intrapartum mortality and neonatal morbidity and mortality did not differ between uncomplicated monochorionic (27/1458 (1.9%)) and dichorionic (107/6288 (1.7%)) twin pregnancies when adjusting for conception by assisted reproductive technologies (adjusted relative risk, 1.07 (95% CI, 0.66-1.75)). No significant difference in the primary outcome was found between the groups on subgroup analyses according to birth order and gestational age at delivery.

CONCLUSION

When vaginal delivery is planned, and delivery occurs at ≥ 32 weeks of gestation with the first twin in cephalic presentation, uncomplicated monochorionic twin pregnancy is not associated with a higher rate of composite intrapartum mortality and neonatal morbidity and mortality compared with dichorionic twin pregnancy. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Chromosomal mosaicism detected by karyotyping and chromosomal microarray analysis in prenatal diagnosis

To investigate the incidence and clinical significance of chromosomal mosaicism (CM) in prenatal diagnosis by G‐banding karyotyping and chromosomal microarray analysis (CMA). This is a single‐centre retrospective study of invasive prenatal diagnosis for CM. From 5758 karyotyping results and 6066 CMA results, 104 foetal cases with CM were selected and analysed further. In total, 50% (52/104) of foetal cases with CM were affected by ultrasound‐detectable phenotypes. Regardless of whether they were singleton or twin pregnancies, isolated structural defects in one system (51.35%, 19/37 in singletons; 86.67%, 13/15 in twins) and a single soft marker (18.92%, 7/37 in singletons; 13.33%, 2/15 in twins) were the most common ultrasound anomalies. Mosaic autosomal trisomy (19.23%, 20/104) was the most frequent type, and its rate was higher in phenotypic foetuses (28.85%, 15/52) than in non‐phenotypic foetuses (9.62%, 5/52). There was no difference in mosaic fractions between phenotypic and non‐phenotypic foetuses based on specimen sources or overall classification. Discordant mosaic results were observed in 16 cases (15.38%, 16/104) from different specimens or different testing methods. Genetic counselling and clinical management regarding CM in prenatal diagnosis remain challenging due to the variable phenotypes and unclear significance. Greater caution should be used in prenatal counselling, and more comprehensive assays involving serial ultrasound examinations, different specimens or testing methods verifications and follow‐up should be applied.

Expectant Management of Monochorionic-Triamniotic Triplets Complicated by Selective In Utero Growth Restriction: Report of 2 Cases

The optimal management of monochorionic-triamniotic (MCTA) triplet pregnancies is not clearly established, and there is no literature to guide management of MCTA complicated with selective intrauterine growth restriction (sIUGR). This gap in knowledge and the concern for higher risk of severe complications have led some medical societies to recommend selective termination of nontrichorionic triplet pregnancies. We sought to report the favourable outcomes of two MCTA complicated by sIUGR expectantly managed at Sainte-Justine Hospital, Montreal, Canada. The first case is of a 42-year-old woman with spontaneous MCTA triplets diagnosed at 18 weeks with type II sIUGR who opted for expectant management. The second patient was a 22-year-old woman with a spontaneous MCTA triplet pregnancy diagnosed at 18 weeks with type III sIUGR. Our experience shows that close serial ultrasounds could potentially allow physicians to foresee fetal deterioration. In our opinion, expectant management should be considered as a management option for MCTA complicated by sIUGR.

Management of monochorionic twins discordant for structural fetal anomalies

OBJECTIVE

To review the perinatal management and outcomes of monochorionic twin pregnancies (MC) discordant for congenital anomalies (DCA).

METHODS

Retrospective, study of all MC DCA cases referred to our tertiary referral center from 1997 to 2018. We excluded cases complicated with twin-to-twin transfusion syndrome, twin anemia-polycythemia sequence, twin reversed arterial perfusion sequence or selective intra-uterine growth restriction. Patients were counseled about the possibility of expectant (EM) or interventional management (selective feticide [SF] or termination of the entire pregnancy [TOP]).

RESULTS

One hundred eight of 4157 (2.6%) MC pregnancies were discordant for anomaly. Fifty two of 108 n(48.1%) underwent SF at a mean gestational age of 31.4 ± 5.9 weeks while 52/108(48.1%) opted for EM. Livebirth rate of the healthy co-twin was similar between the two groups (SF: 88.5% vs EM: 82.7%, P = .87). In the SF group, six healthy co-twins (6/52, 11.5%) died 5.3 ± 3.1 days after SF of the abnormal co-twin. In the EM group, in-utero demise of the abnormal twin occurred in 9 of 52 (17.3%) of the cases and was followed by the spontaneous demise of the healthy co-twin in 4 of 9 (44.4%) of these cases.

CONCLUSION

Selective feticide does not seem to significantly alter survival of the healthy co-twin compared to EM.

US Evaluation of Twin Pregnancies: Importance of Chorionicity and Amnionicity

The twin birth rate is increasing in the United States. Twin pregnancies can be dichorionic or monochorionic (MC). MC twins account for 20% of twin pregnancies but 30% of all-cause pregnancy-related complications. This article describes the imaging findings that establish chorionicity and amnionicity. Ideally, these are established in the first trimester when accuracy is high, but they can also be determined later in pregnancy. Complications unique to MC twin pregnancy include twin-twin transfusion syndrome, twin anemia polycythemia sequence, twin reversed arterial perfusion sequence, and selective fetal growth restriction. The US features, staging systems, and management of these complications are reviewed, and the consequences of MC twin demise are illustrated. Ongoing surveillance for these conditions starts at 16 weeks gestation. Monoamniotic (MA) twins are a small subset of MC twins. In addition to all of the MC complications, specific MA complications include cord entanglement and conjoined twinning. Radiologists must be able to determine chorionicity and amnionicity and should be aware of potential complications so that patients may be referred to appropriate regional specialized centers. A proposed algorithm for referral to specialized fetal treatment centers is outlined. Online supplemental material is available for this article. ^©RSNA, 2019.

Delivery timing after laser surgery for twin-twin transfusion syndrome

OBJECTIVE

To compare outcomes of twin-twin transfusion syndrome (TTTS) patients who underwent early elective delivery vs. expectant management.

STUDY DESIGN

Retrospective study of monochorionic diamniotic twins who underwent laser surgery for TTTS and had dual survivors at 32 weeks. Patients who underwent elective delivery between 32 0/7 to 35 6/7 weeks ("early elective group") were compared with all patients who delivered ≥36 0/7 weeks ("expectant management group"). The primary outcome was a composite of fetal and neonatal morbidity.

RESULTS

The final study population was comprised of 15 early elective and 119 expectant management patients. Those in the early elective group were seven times more likely to experience the primary outcome (OR 7.38 [2.01-27.13], p = 0.0026).

CONCLUSION

Among patients who underwent laser surgery for TTTS who had dual survivors at 32 weeks, elective delivery prior to 36 weeks did not appear to be protective.

miRNA-210-3p regulates trophoblast proliferation and invasiveness through fibroblast growth factor 1 in selective intrauterine growth restriction

Selective intrauterine growth restriction (sIUGR), which affects approximately 10%-15% of monochorionic (MC) twin pregnancies, is highly associated with intrauterine foetal death and neurological impairment in both twins. Data suggest that unequal sharing of the single placenta is the main contributor to birth weight discordance. While MC twins and their placenta derive from a single zygote and harbour almost identical genetic material, the underlying mechanisms of phenotypic discrepancies in MC twins remain unclear. MicroRNAs are small non-coding RNA molecules that regulate gene expression but do not change the DNA sequence. Our preliminary study showed that microRNA-210-3p (miR-210-3p) was significantly upregulated in the placental share of the smaller sIUGR twin. Here, we investigate the potential role of miR-210-3p in placental dysplasia, which generally results from dysfunction of trophoblast cells. Functional analysis revealed that miR-210-3p, induced by hypoxia-inducible factor 1α (HIF1α) under hypoxic conditions, suppressed the proliferation and invasiveness of trophoblast cell lines. Further RNA sequencing analysis and luciferase reporter assays were performed, revealing that fibroblast growth factor 1 (FGF1) is an influential target gene of miR-210-3p. Moreover, correlations among miR-210-3p levels, HIF1α and FGF1 expression and the smaller placental share were validated in sIUGR specimens. These findings suggest that upregulation of miR-210-3p may contribute to impaired placentation of the smaller twin by decreasing FGF1 expression in sIUGR.

Deep-learned placental vessel segmentation for intraoperative video enhancement in fetoscopic surgery

INTRODUCTION

Twin-to-twin transfusion syndrome (TTTS) is a potentially lethal condition that affects pregnancies in which twins share a single placenta. The definitive treatment for TTTS is fetoscopic laser photocoagulation, a procedure in which placental blood vessels are selectively cauterized. Challenges in this procedure include difficulty in quickly identifying placental blood vessels due to the many artifacts in the endoscopic video that the surgeon uses for navigation. We propose using deep-learned segmentations of blood vessels to create masks that can be recombined with the original fetoscopic video frame in such a way that the location of placental blood vessels is discernable at a glance.

METHODS

In a process approved by an institutional review board, intraoperative videos were acquired from ten fetoscopic laser photocoagulation surgeries performed at Yale New Haven Hospital. A total of 345 video frames were selected from these videos at regularly spaced time intervals. The video frames were segmented once by an expert human rater (a clinician) and once by a novice, but trained human rater (an undergraduate student). The segmentations were used to train a fully convolutional neural network of 25 layers.

RESULTS

The neural network was able to produce segmentations with a high similarity to ground truth segmentations produced by an expert human rater (sensitivity = 92.15% ± 10.69%) and produced segmentations that were significantly more accurate than those produced by a novice human rater (sensitivity = 56.87% ± 21.64%; p < 0.01).

CONCLUSION

A convolutional neural network can be trained to segment placental blood vessels with near-human accuracy and can exceed the accuracy of novice human raters. Recombining these segmentations with the original fetoscopic video frames can produced enhanced frames in which blood vessels are easily detectable. This has significant implications for aiding fetoscopic surgeons-especially trainees who are not yet at an expert level.

Real-time computerized video enhancement for minimally invasive fetoscopic surgery

Background

The only definitive treatment for twin-to-twin transfusion syndrome is minimally invasive fetoscopic surgery for the selective coagulation of placental blood vessels. Fetoscopic surgery is a technically challenging operation, mainly due to the poor visibility conditions in the uterine environment. We present the design of an algorithm for the computerized enhancement of fetoscopic video and show that the enhanced video increases the ability of human users to identify blood vessels within fetoscopic video rapidly and accurately.

Methods

A computer algorithm for the enhancement of fetoscopic video frames was created. First, optical fiber artifacts were removed via a modification of unsharp masking. Second, image contrast was increased via Contrast Limited Adaptive Histogram Equalization (CLAHE). Third, the effect of contrast enhancements on stationary features was removed by normalizing to a windowed mean of the video frames. Fourth, color information was reincorporated by combining the mean-normalized result with the unnormalized contrast enhanced image using the soft light blending algorithm. Medical trainees (n = 16) were recruited into a study to validate the algorithm. Subjects were shown enhanced or unenhanced fetoscopic video frames on a screen and were asked to identify whether a randomly placed marker fell on a blood vessel or on background. The accuracy of their responses was recorded.

Results

On the subset of images where subjects had the lowest mean accuracy in identifying the placement of the marker, subjects performed better when viewing video frames enhanced by the computer (accuracy 74.27%; SE 0.97) than when viewing unenhanced video frames (accuracy 63.78%; SE 2.79). This result was statistically significant (p < 0.01).

Conclusion

Real-time computerized enhancement of fetoscopic video has the potential to ease the readability of video in poor lighting conditions, thus providing a benefit to the surgeon intraoperatively.

Role of ultrasonography in the management of twin gestation

Twins represent 1%-2% of all pregnancies, yet continue to account for a disproportionate share of neonatal adverse events including neonatal intensive care admission, morbidity, and mortality. Ultrasonography is central to the proper diagnosis of the type of twinning. Ideally, ultrasonography is performed before 14 weeks of gestation to determine chorionicity and amnionicity. Correct identification of the chorionicity in a twin pregnancy facilitates proper counseling and management of the gestation, including ultrasonography follow-up. Herein, the different types of twinning are reviewed, together with the implications for ultrasonography monitoring of each specific type of twin gestation.

Ethical considerations in the care of complicated twin pregnancies

Twin gestations are increasing in prevalence worldwide, and are potentially subject to medical complications which present uniquely complex ethical and psychosocial challenges for the pregnant patient and obstetrician to navigate. In this article, we explore these issues as they relate to medical decision-making in cases of discordant growth and discordant anomalies in both monochorionic and dichorionic twin pregnancies, including those affected by twin-twin transfusion syndrome, with particular attention to scenarios in which the individual fetuses hold competing interests. For each of these scenarios, we consider how decisions may positively or negatively impact one or both fetuses, and how familiarity with population outcomes, as well as sensitivity to the complex psychosocial circumstances surrounding these pregnancies, can support and inform shared decision-making.