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

Placental recruitment after spontaneous single fetal demise in monochorionic diamniotic twin pregnancies

INTRODUCTION

The incidence of single fetal demise in monochorionic diamniotic twin pregnancies is approximately 7.5%. In single fetal demise cases, the placental region of the demised fetus is almost infarcted or necrotic at the time of delivery. Further, it has been reported that in some cases, a surviving fetus uses all regions of the placenta after a single fetal demise. Thus, in the present study, we investigated the incidence and natural prognosis of placental recruitment in spontaneous single fetal demise cases over a period of 11 years.

METHODS

All 306 monochorionic diamniotic twin pregnancies that were delivered between 2011 and 2021 in our institution were included in this retrospective cohort study. The placenta and umbilical cord were investigated, and the type of anastomosis was identified by color injection. Furthermore, the number and direction of arteriovenous anastomoses were recorded.

RESULTS

There were eight single fetal demise cases, excluding cases of twin-reversed arterial perfusion sequence and after fetoscopic laser photocoagulation. The placental region of six demised fetuses had an infarction or necrotic region. In two cases, an infarction or necrosis was not observed, and the surviving fetus used all regions of the placenta.

DISCUSSION

The surviving fetus in monochorionic diamniotic twin pregnancies with superficial anastomoses can use all regions of the placenta, even after a spontaneous single fetal demise. Further studies are needed to determine the difference between such cases and in those in which only the localized regions of the placenta can be used.

Fetal anemia in monochorionic twins: a review on diagnosis, management, and outcome

INTRODUCTION

Monochorionic twins may develop fetal anemia when blood is unequally distributed via the placental vascular anastomoses. This review focuses on the causes of fetal anemia in complicated monochorionic twins and highlights the differences in management and outcome.

AREAS COVERED

Fetal anemia can occur in the context of twin anemia polycythemia sequence (TAPS), chronic twin-twin transfusion syndrome (TTTS) and acute peripartum TTTS, and in cotwins after single fetal demise. Diagnosis of fetal anemia is based on abnormal Doppler ultrasound measurements. Management options include fetoscopic laser surgery, intrauterine blood transfusion, or expectant management, depending on the type of complication and the severity of the disease. In all complications, fetal anemia may lead to perinatal mortality, neonatal morbidity, severe cerebral injury, and long-term neurodevelopmental impairment. In TAPS specifically, anemic donors may also show bilateral deafness.

EXPERT OPINION

Knowledge on the diagnosis and optimal treatment in TTTS is nowadays widespread, but caregivers often fail to distinguish TAPS from acute peripartum TTTS at birth. A full blood count including reticulocyte count is required, and placental dye injection is extremely helpful to reach the correct diagnosis and establish the optimal management.

Effect of Superficial Anastomoses on Circulatory Dynamics in Twin-Twin Transfusion Syndrome

The role of superficial anastomoses in the survival of fetuses with twin-twin transfusion syndrome after fetoscopic laser photocoagulation is unknown. This study aimed to evaluate how superficial anastomoses affect the circulatory dynamics of both fetuses with twin-twin transfusion syndrome using ductus venous Doppler waveforms. We included all twin-twin transfusion syndrome (TTTS) patients who underwent fetoscopic laser photocoagulation in our institution from 2006 to 2019; fetal demise cases after fetoscopic laser photocoagulation were excluded. We recorded ductus venous Doppler waveforms on the same day or one day before fetoscopic laser photocoagulation and one day after fetoscopic laser photocoagulation and measured the ductus venous pulsatility index and velocity ratios. We compared these z-scores of donor and recipient twins between a group without superficial anastomoses and the groups with arterio-arterial or veno-venous anastomoses. A total of 115 surviving TTTS placentas after fetoscopic laser photocoagulation were analyzed. The ductus venous pulsatility index and all ratios were better in recipient twins with arterio-arterial anastomoses than in those without. The a-wave-related ratios were better in recipient twins with veno-venous anastomoses than in those without. Superficial anastomoses reduced the blood volume and arterio-arterial anastomoses protected the diastolic cardiac function in recipient twin-twin transfusion syndrome twins before fetoscopic laser photocoagulation. Superficial anastomoses in TTTS equilibrate blood pressure between donor and recipient twins.

Neonatal management and outcome in complicated monochorionic twins: What have we learned in the past decade and what should you know?

Monochorionic (MC) twin pregnancies are at increased risk of neonatal morbidity and mortality due to the shared placenta with vascular connections that can give rise to various complications, including twin-twin transfusion syndrome, twin anemia polycythemia sequence (TAPS), selective fetal growth restriction, and other hematological imbalances at birth. Each complication presents its own challenges and considerations in the neonatal period. Measurement of hemoglobin levels and reticulocyte count is required to establish a correct diagnosis. Placenta dye injection is needed to properly distinguish between the various conditions. Risk factors for adverse outcome in MC twins include prematurity, severe cerebral injury, and the type of MC pregnancy complication. We, therefore, recommend cerebral ultrasound examinations in all complicated MC twins at birth to rule out a severe brain injury. Lastly, we strongly encourage screening for hearing loss using automated auditory brainstem response in all spontaneous TAPS donors to prevent permanent speech development delay.

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.

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.

In vitro simulation of acute feto-fetal transfusion in case of single intrauterine fetal death in monochorionic twins

INTRODUCTION

Thanks to shared circulation in monochorionic twins, single intrauterine fetal death (IUD) may lead to acute feto-fetal transfusion (aFFTR). The objective of the study was to describe our model of aFFTR simulation after IUD in monochorionic (MC) twins.

METHODS

Prospective study analyzed 99 fresh MC placentas with the physiological course. A specially designed protocol was used for the preparation and analysis of the placentas. A pair of infusion sets fixed together using a mechanical mercury sphygmomanometer cuff was connected to the cannulated umbilical arteries. The tonometer was pressurized up to 30 and 40 mmHg. A positive finding of aFFTR was determined as the amount exceeding 1 ml of dye flowed out of the umbilical cord simulating a dead fetus. The number and types of anastomoses, types, and distances between cords insertions, and the size of the placental areas for each fetus were also statistically analyzed. The placental angioarchitecture with and without proven aFFTR was statistically compared, odds ratio (OR) and multivariable logistic analysis were performed.

RESULTS

A total of 49/99 (49.5%) cases of aFFTR was proven, and the average transfusion time of 1 ml was 30 s (19-46 s). aFFTR was present in 49/78 (62.8%) of placentas with arterio-arterial (AA) anastomosis. The median diameter of AA anastomoses with the present, and absent aFFTRF was 2.0 mm and 1.0 mm, respectively. The proven interfetal transfusion was 8%, 31%, and 61% in AA anastomoses with a diameter below 0,5 mm, 0,5-1,5 mm, and above 1,5 mm, respectively (p < 0,001). AA anastomoses diameter >1.5 mm had OR of 44.2 (95% CI 5.54-352.39). In the case of coexistence of AA anastomosis and umbilical cord distance ≤5th percentile, the aFFTRF occurred in 90.9%.

DISCUSSION

The potential risk of aFFTR in monochorionic twins is mainly due to the presence and nature of AA anastomoses. The diameter and length of the vessels play a crucial role, which is clinically related to the distance of the umbilical cords insertions.

Vascular anastomoses in intrauterine growth in monochorionic twins

Objectives To evaluate the impact of placental anastomoses on the intrauterine growth of monochorionic (MC) twins. Methods A prospective study was conducted in a group of 53 MC twins. Intrapartally umbilical cords were clamped to identify placental sides corresponding to each twin. The postnatal dye injection technique was administered to evaluate vascular anastomoses, their number and type and visualize placental territory sharing patterns. Data from digital analysis were correlated with obstetrical follow-up. Results Vascular anastomoses were revealed in 88.7% of cases. Arteriovenous (AV) anastomoses occurred in 75.4% and arterioarterial (AA) in 71.1% while venovenous (VV) in 26.4%. In the subgroup of MC twins without placental anastomoses, significantly higher birthweight difference and discordance were revealed when compared to MC twins without anastomoses (382.0 vs. 22 g; P = 0.03 and 49.14% vs. 16.02%; P = 0.03). On the other hand, in subgroups of MC twins with at least one AA anastomosis, twins' birthweights were similar (p = ns) despite significantly higher placental territory sharing discordance (30.44% vs. 15.81%; P = 0.31). Conclusions Vascular anastomoses have a major impact on the intrauterine growth of MC twins. In certain cases, they may cause specific complications; however, in general, they regulate intertwin blood exchange and may compensate unequal placental territory.

Twin-Twin Transfusion Syndrome with Anemia-Polycythemia: Prevalence, Characteristics, and Outcome

The aim of this study was to estimate the prevalence of co-existing anemia-polycythemia (AP) in twin pregnancies with twin-twin transfusion syndrome (TTTS) prior to laser surgery, and to evaluate the characteristics and outcomes in TTTS twins with and without AP. All TTTS cases treated with laser between 2001 and 2019 were retrospectively reviewed for the presence of AP before surgery. AP was defined as delta middle cerebral artery–peak systolic velocity > 0.5 multiples of the median. The primary outcome was a composite of perinatal survival and severe neurodevelopmental impairment (NDI). Secondary outcomes included procedure-related characteristics, severe neonatal morbidity, and disease-free survival. In total, 66% (461/696) of TTTS twin pregnancies were eligible for analysis. AP was detected in 15% (70/461) of the TTTS twins prior to laser surgery. Gestational age at laser was higher in the TTTS+AP group compared to the TTTS-only group—21.0 weeks (interquartile rage (IQR): 18.8–24.0) versus 19.3 weeks (IQR: 17.3–21.9), respectively (p < 0.0001). Fewer placental anastomoses were detected in the TTTS+AP group than in the TTTS-only group—five (IQR: 4–6) versus six (IQR: 5–8), respectively (p < 0.0001). Perinatal survival was 77% (599/782) in the TTTS-only group and 83% (118/142) in the TTTS+AP group (p = 0.130). Severe NDI was 8% (28/370) in TTTS-only and 3% (2/74) in TTTS+AP. TTTS-only twins showed more severe neonatal morbidity than twins with TTTS+AP—23% (132/575) versus 11% (13/115), respectively (p = 0.005). Disease-free survival was lower in the TTTS-only group compared to the TTTS+AP group—62% (341/548) versus 73% (72/98), respectively (p = 0.046). Thus, AP complicates 15% of TTTS twins prior to laser. TTTS+AP twins show a different placental angioarchitecture, a later time of onset of the disease, and a more favorable outcome.

The roles of superficial anastomoses in twin-twin transfusion syndrome

OBJECTIVE

We aimed to evaluate whether types of vascular anastomoses affect fetal demise (FD) in twin-twin transfusion syndrome (TTTS) after fetoscopic laser photocoagulation (FLP).

METHODS

All TTTS patients who underwent FLP in our institution from 2005 to 2017 were included. We described vascular anastomoses during FLP as either arterio-arterial (AA), veno-venous (VV), or arterial-venous (AV), and abnormal fetal Doppler waveforms before FLP. We also analyzed risk factors for FD following FLP.

RESULTS

In total, 184 TTTS placentas following FLP were analyzed (36 cases of donor-only FD, 12 cases of recipient-only FD, 3 cases of double FD, and 133 cases of both alive). AA anastomoses prevalence, absent or reverse end-diastolic velocity of umbilical artery (UAAREDV) of donor before FLP, gestational age at the time of FLP and operation time of FLP were independent risk factors for donor FD. VV anastomoses prevalence and UAAREDV of recipient before FLP were independent risk factors for recipient FD. VV anastomoses prevalence was higher in double FD cases than in FD of one twin or both alive (p = 0.002). AV anastomoses number and number of cases with more AV anastomoses from donor to recipient were not significantly different between FD and non-FD cases.

DISCUSSION

AA anastomoses are associated FD of the donor following FLP and may protect the donor from hypovolemia before FLP. VV anastomoses are detected more frequently in FD of the recipient and double FD placentas following FLP and may rescue hypervolemia of the recipient or circulations of both fetuses before FLP.

The value of ultrasound in predicting isolated inter-twin discordance and adverse perinatal outcomes

PURPOSE

To investigate the value of ultrasound approaching delivery to predict isolated inter-twin discordance and adverse perinatal outcomes.

METHODS

We retrospectively included twin pregnancies with sonography approaching delivery in ten maternal-foetal medicine centres in China from 2013 to 2014. Estimated foetal weight (EFW) and inter-twin EFW disparity (EFWD) were calculated based on biometry parameters. Percentage errors between EFW and actual birthweight or between EFWD and actual inter-twin disparity were calculated. ROC curves and multiple logistic regression were applied to evaluate the ability of EFWD to predict inter-twin disparity ≥ 25%, stillbirth, asphyxia and admission to a neonatal intensive unit (NICU). Chorionicity-stratified analysis was further performed.

RESULTS

Two hundred sixty-six monochorionic and 760 dichorionic twin pregnancies were analysed. The percentage errors in foetal weight estimations were 7-13%, whereas percentage errors in the estimation of inter-twin disparity were nearly 100%. Among eight formulas, Hadlock1 performed best, with a detectable rate of 65% and a false positive rate of 5% when predicting inter-twin disparity ≥ 25%. EFWD ≥ 22% was strongly associated with stillbirth (OR = 4.17, 95% CI 1.40-12.40) and NICU admission (OR = 3.48, 95% CI 2.03-5.97) after adjustment for gestational age, parity and abnormal umbilical systolic/diastolic ratio. Ultrasound had better predictive ability in monochorionic twins.

CONCLUSION

The predictive value of ultrasound for isolated inter-twin discordance and adverse perinatal outcomes was limited, which was possibly due to the magnifying of systematic errors in the disparity estimation compared with weight estimation. Despite this, abnormal biometry was an independent contributor for the poor prognosis of neonates.

Roles of venovenous anastomosis and umbilical cord insertion abnormalities in birthweight discordance in monochorionic-diamniotic twin pregnancies without twin-twin transfusion syndrome

AIM

We evaluated risk factors for birthweight discordance in monochorionic diamniotic (MCDA) twin pregnancies without twin-twin transfusion syndrome (TTTS).

METHODS

We investigated all MCDA twin placentas injected with colored dye at our institution between 2007 and 2015. We excluded pairs of twins with TTTS, fetal demise, or severe fetal malformation. All pairs of twins were assigned to the discordant group (birthweight discordance ≥ 25%) or the concordant group (birthweight discordance < 25%). In each pair of twins, we described vascular anastomoses as either arterioarterial, venovenous (VV), or arterial-venous, and abnormal umbilical cord insertion as either marginal or velamentous. We also recorded placental sharing discordance.

RESULTS

A total of 150 placentas were analyzed. The incidence of VV anastomosis in the discordant group (40%) was significantly higher than that in the concordant group (12%, P = 0.005). Unilateral abnormal umbilical cord insertion was significantly more common in the discordant group (85%) than in the concordant group (38%, P < 0.001). Placental sharing discordance was seen more frequently in the discordant group than in the concordant group. Multiple logistic analysis revealed that VV anastomosis (odds ratio: 4.7; 95% confidence interval: 1.2-18.6, P < 0.01) and unilateral abnormal umbilical cord insertion of the smaller twin (odds ratio: 5.7; 95% confidence interval: 1.4-22.9, P < 0.01) were independent risk factors for birthweight discordance.

CONCLUSION

VV anastomoses and unilateral abnormal umbilical cord insertion of the smaller twin are independent risk factors for birthweight discordance in MCDA twin pregnancies without TTTS.

Cardiac Manifestations of Twin–to–Twin Transfusion Syndrome

This review addresses the physiology of monochorionic diamniotic (MC/DA) twins and the potential for twin–twin transfusion syndrome (TTTS). It focuses on the underlying cardiovascular pathophysiology of TTTS and the cardiovascular impact of TTTS for both the recipient and the donor twin. It explains the principles for assessment and monitoring of these cardiovascular changes and how these may be used to guide pregnancy management. Finally, it describes the effect of treatment on the altered hemodynamics and how this can influence pregnancy and perinatal management, as well as longer-term follow-up.