Uncomplicated Monochorionic Diamniotic Twin Pregnancies Research Articles

Пренатальная эхокардиографическая методика спекл-трекинг в исследовании сердца у плодов из монохориальных диамниотических двоен с неосложненным и осложненным течением беременности

Aim: to compare left ventricular (LV) and right ventricular (RV) global longitudinal strain (GLS) in uncomplicated monochorionic, diamniotic (MCDA) twin pregnancy with twin-to-twin transfusion syndrome (TTTS) and selective intrauterine growth restriction (sIUGR) of one fetus and uncomplicated singleton pregnancy. Patients and Methods: the study included 60 pregnant women divided into 2 groups. Group 1 included 25 women with an uncomplicated singleton pregnancy. Group 2 included 35 women with an MCDA twin pregnancy. Pregnancy was complicated with Quintero stage I-III TTTS in 10 women and sIUGR in 10 women. No MCDA twin pregnancy complications were reported in 15 women. Ventricular GLS (by speckle tracking echocardiography) and fetal ejection fraction were measured during the study. Results: significant differences in ventricular GLS were found between fetuses in singleton and uncomplicated MCDA twin pregnancies (for RV, -20.1±2.4 and -23.3±2.5, respectively, p=0.020; for LV, -20.9±2 and -24.5±2.3, respectively, p=0.005); donor and recipient fetuses in TTTS (for LV, -27. 2 [-29.5; -24.6] and -20.6 [-23.1; -17.6], respectively, p=0.005, for RV -26.7 [-30.9; -24.6] and -19.1 [-23.5; -17.9], respectively, p=0.005); recipient fetus before and after fetoscopic laser coagulation (FLC) of placental anastomoses; and twins with sIUGR. Thus, fetal ventricular GLS is greater in uncomplicated MCDA twin pregnancies than in singleton pregnancies. Hemodynamics improve after FLC of placental anastomoses in the recipient fetus in TTTS. sIUGR in MCDA twin pregnancy also affects cardiac function in twins, which requires further study. Conclusions: this paper discusses pilot data on the assessment of fetal cardiac function in MCDA twin pregnancy by speckle tracking echocardiography, which detects early changes in fetal myocardial function and reliably monitors changes in cardiac function over time. KEYWORDS: fetal echocardiography, monochorionic diamniotic twins, fetal surgery, speckle tracking echocardiography. FOR CITATION: Kosovtsova N.V., Markova T.V., Chumarnaya T.V., Gusarova E.O., Pavlichenko M.V., Pospelova Ya.Yu., Solov'eva O.E. Prenatal speckle tracking echocardiography for fetal heart study in uncomplicated and complicated monochorionic diamond twin pregnancies. Russian Journal of Woman and Child Health. 2024;7(3):192–198 (in Russ.). DOI: 10.32364/2618-8430-2024-7-3-1.

Two Year Neurodevelopmental Outcome after Fetoscopic Laser Therapy for Twin-Twin Transfusion Syndrome: Comparison with Uncomplicated Monochorionic Diamniotic Twins.

Twin-twin Transfusion Syndrome (TTTS) represents a significant complication in monochorionic twin pregnancies, caused by an unbalanced shunting of blood through intertwin placental vascular anastomoses. Despite advances in fetoscopic laser surgery, TTTS is still associated with a high rate of cerebral injury. However, there are no studies comparing these pregnancies with uncomplicated monochorionic diamniotic (MCDA) twin pregnancies, establishing the baseline risk of neurodevelopmental impairment. The aim of this study is to evaluate the odds of neurodevelopmental impairment in MCDA twins who undergo fetoscopic laser surgery for twin-twin transfusion syndrome, in comparison to a cohort of uncomplicated MCDA twin pregnancies. This is a retrospective cohort study of children born from MCDA twin pregnancies at a single center between 2008 and 2019. A routine, standardized follow-up assessment was conducted at a minimum of 2 years after delivery. The primary outcome of this was a 2 year neurodevelopmental impairment. Neurological, motor, and cognitive development was assessed by using the revised Brunet-Lézine scale. 176 children met the enrolment criteria. Of these, 42 (24%; TTTS group) underwent fetoscopic laser surgery for TTTS during pregnancy, and 134 (76%; uncomplicated MCDA group) were uncomplicated MCDA pregnancies. The primary outcome was found in four children (9.52%) in the TTTS group and ten children (7.46%) in the uncomplicated MCDA group (p = 0.67, aOR 2.82, 95% CI 0.49-16.23). Major neurologic impairment was found in 2.38% after fetoscopic laser surgery and 1.49% in uncomplicated MCDA twins (p = 0.70, aOR 0.97, 95% CI 0.22-4.24). The data were adjusted by birth order, birth weight, and gestational age at birth. The outcome in MCDA twins who underwent fetoscopic laser surgery for TTTS is comparable to the outcome in uncomplicated MCDA twins. Our findings emphasize the need for long-term neurodevelopmental follow-ups in all children from monochorionic twin gestations.

Fetal ventricular strain in uncomplicated and selective growth-restricted monochorionic diamniotic twin pregnancies and cardiovascular response in pre-twin-twin transfusion syndrome.

ABSTRACTObjectivesOur primary aim was to confirm whether intertwin discordance in ventricular strain and ductus venosus (DV) time intervals predicts twin–twin transfusion syndrome (TTTS). Secondary aims were to create gestational‐age ranges for ventricular strain in uncomplicated monochorionic diamniotic (MCDA) twin pregnancies without selective intrauterine growth restriction (sIUGR) and to characterize the relationship of ventricular strain with gestational age in MCDA twin pregnancies with sIUGR that did not develop TTTS.MethodsIn the period 2015–2018, we enrolled 150 MCDA twin pregnancies consecutively into this prospective, blinded study of global longitudinal left and right ventricular strain. With the observer blinded to twin pairing and pregnancy outcome, videoclips of the four‐chamber view, which had been recorded during ultrasound surveillance in the usual window for development of TTTS (16–26 completed gestational weeks), underwent offline measurement of strain. Uncomplicated MCDA twin pregnancies, without sIUGR, were used to test the association between strain, gestational age and estimated fetal weight using mixed‐effects multilevel regression. Inter‐rater reliability was tested in 208 strain measurements in 31 fetuses from pregnancies which did not develop TTTS and within‐fetus variation was assessed in 16 such fetuses, in which multiple four‐chamber views were taken on the same day. The effect of sIUGR on strain in otherwise uncomplicated MCDA twin pregnancy was analyzed. MCDA twin pregnancies were defined as ‘pre‐TTTS’ when, having been referred for TTTS evaluation, they did not satisfy Quintero staging criteria, but subsequently developed TTTS requiring laser treatment. MCDA pregnancies which did not develop TTTS comprised the ‘non‐TTTS’ group. Cardiovascular parameters measured in these cases included tissue Doppler parameters and DV early filling time as a percentage of the cardiac cycle (DVeT%). Intertwin strain and DVeT% discordance was compared between non‐TTTS and pre‐TTTS cases, matched for gestational age.ResultsPaired strain data were available for intertwin comparison in 127/150 MCDA twin pregnancies, comprising 14 pre‐TTTS and 113 non‐TTTS pregnancies, after exclusions. Scans were collected at a median frame rate of 97 (range, 28–220) Hz. Laser therapy was performed at a median gestational age of 20.6 (range, 17.2–26.6) weeks. There were no group differences in right (RV) or left (LV) ventricular strain discordance between 68/113 non‐TTTS and 13/14 pre‐TTTS MCDA twin pregnancies < 20 completed gestational weeks (RV, P = 0.338; LV, P = 0.932). DVeT% discordance > 3.6% was found in eight of 13 pre‐TTTS pregnancies. In non‐TTTS pregnancies, the estimated variability in ventricular strain within each twin during the day was high (RV, 19.7; LV, 12.9). However, within each pair (intertwin variation), variability was low (RV, 5.5; LV, 2.9). Interclass correlation reflecting the proportion of total variability represented by the variability between twin pairs was low (RV, 0.22; LV, 0.18). Both RV (P < 0.001) and LV (P = 0.025) strain showed a negative association with gestational age. Among non‐TTTS MCDA twin pregnancies, LV strain was, on average, higher by 1.83 in sIUGR compared with normally grown fetuses (P = 0.023), with no statistically significant difference in RV strain (P = 0.271).ConclusionsAlthough ventricular strain has been reported previously as a possible predictor of developing TTTS, in this blinded, prospective study, we found no significant intergroup differences in ventricular strain in pre‐TTTS compared with age‐matched non‐TTTS MCDA twin pregnancies. We recommend using DVeT% discordance as a more practical screening tool in MCDA twin pregnancies. This study also provides new information on the changes with gestational age, and the biological and technical variation, of global longitudinal ventricular strain in uncomplicated MCDA twin pregnancies and those with isolated sIUGR. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

881: The optimal timing of induction of labor in uncomplicated twin pregnancy

Recent guidelines recommend the planned delivery in twin pregnancy as 38 weeks for uncomplicated dichorionic twin pregnancies and as 34-37+6 weeks for uncomplicated monochorionic diamniotic twin pregnancies. However, the optimal timing of induction of labor in twin pregnancies has not been well studied. In the current study, we compared the pregnancy and neonatal outcomes between women with induction at 37 weeks and those who were nonintervention at 37 weeks and allowed the pregnancy to progress after the time. The study population consisted of 1228 term twin pregnant women who were candidates for trial of labor. They were divided into 2 groups: group 1, women who were planned as induction of labor at 37-37+6 weeks (induction group, n=488 in dichorionic twin, 143 in monochorionic twin); group 2, women who were nonintervention at 37 weeks and allowed the pregnancy to progress after the time. (expectant management group, n=384 in dichorionic twin, 92 in monochorionic twin). The timing of induction after 38 weeks in group 2 was at the discretion of the attending physician. Women who delivered due to obstetric indication (ex. preeclampsia, oligohydramnios, fetal growth restriction) and cases with fetal death in utero or fetal anomaly were excluded. The primary outcome was cesarean section rate and perinatal outcomes (Apgar scores, neonatal intensive care unit (NICU) admission, umbilical cord blood gases, neonatal morbidity). No significant differences were observed in cesarean delivery rate between two groups regardless of chorionicity. In monochorionic twin pregnancies, neonates born to women in group 2 (expectant management group) had higher risk for admission to NICU and lower pH in cord blood than neonates in group 1. In dichorionic twin pregnancies, the perinatal outcomes were not different between the two groups. Induction of labor at 37 weeks resulted in reduced adverse perinatal outcomes compared to expectant management in monochorionic twin pregnancies. The optimal timing of induction of labor in dichorionic pregnancies beyond 38 weeks needs further studies.

MicroRNA changes in maternal serum from pregnancies complicated by twin-twin transfusion syndrome: A discovery study.

ObjectiveMicroRNAs (miRNAs) are used as biomarkers in cardiovascular disease and cancer. miRNAs are involved in placental development but have not previously been investigated in twin‐twin transfusion syndrome (TTTS). Our aim is to explore the miRNA profile of TTTS pregnancies.MethodInitial miRNA profiling was performed using a reverse transcription polymerase chain reaction (RT‐PCR) panel on maternal serum samples taken from five women prior to fetoscopic laser ablation for TTTS and compared with serum samples from five women with uncomplicated monochorionic diamniotic twin pregnancies. Validation RT‐PCR was performed in an additional cohort of eight TTTS pregnancies and eight uncomplicated pregnancies.ResultsMedian gestational age at sampling in the TTTS and control groups was 20+0 weeks (interquartile range [IQR], 19+4‐20+0) and 20+2 weeks (IQR, 20+0‐20+2), respectively. All samples passed quality control. One control sample was excluded as a biological outlier. Thirty‐one of 752 miRNAs were significantly different: 17 were upregulated and 14 downregulated in the TTTS group, although they did not remain significant following Benjamini‐Hochberg correction for multiple testing. The six miRNAs chosen for validation demonstrated no significant difference.ConclusionThis is the first study to investigate miRNA changes in TTTS pregnancies. We did not demonstrate a statistically significant difference in miRNAs in TTTS pregnancies, but further investigation is required.

Recipient umbilical artery elongation (redundancy) in twin-twin transfusion syndrome

Chronic hypertension in adults causes arterial lengthening in major arteries, but the effects of early fetal hypertension on the twin-twin transfusion syndrome recipient's vascular architecture remains unknown. We hypothesize that arterial cord redundancy is related to recipient hypertension and subsequent heart failure. Our objectives were to: (1) establish a 3-dimensional color Doppler ultrasound method of measuring umbilical arterial length relative to its corresponding venous segment in the umbilical cord using artery vein angle; (2) compare recipient artery vein angle to gestational age-matched controls; and (3) test the association of artery vein angle with recipient heart failure. We compared 3 groups prospectively: twin-twin transfusion syndrome pregnancies undergoing fetoscopic laser surgery (preoperatively) and 2 groups of gestational age-matched controls: uncomplicated monochorionic-diamniotic twin pregnancies and healthy singletons. Using a 3-dimensional color-Doppler volume image of 5 cm of cord near the placental insertion, we traced the umbilical artery and vein producing umbilical artery:vein length, (artery vein index) and measured the artery vein angle between umbilical artery and vein. Correlation of artery vein angle to twin-twin transfusion syndrome stage, maximum vertical pocket, umbilical arterial indices, ductus venosus Doppler, and brain natriuretic peptide were performed. We used pulsed-wave and tissue Doppler to measure tissue Doppler velocities and indexed cardiac output and correlated these with artery vein angle. Comparative statistics, including multivariable linear regression, examined the relationship between umbilical arterial Doppler indices and artery vein angle. Artery vein angle and artery vein index correlated significantly (R2, 0.86; P < .0001), hence, artery vein angle was used for analysis. Mean artery vein angle was 33.1 ± 31.5 degrees in recipients (n= 44), 9.5 ± 6 degrees in monochorionic-diamniotic (n= 11; 22 fetuses), and 8.9 ± 8.3 degrees in singleton controls (n= 16) (P < .001). An artery vein angle ≥26 degrees (>95th percentile for controls) was measured in 52% recipients. Artery vein angle was higher in twin-twin transfusion syndrome stage 3R vs 1 (P= .001). Artery vein angle increased with increasing umbilical arterial pulsatility index (P < .001), and decreased with increasing resistance index (P= .02) after adjusting for gestational age. Interrater agreements to categorize abnormal artery vein angle values was 95% (P < .001). Abnormal ductus venosus Doppler and elevated recipient amniotic fluid N-terminal pro-brain natriuretic peptide/protein levels correlated significantly with artery vein angle. Abnormal artery vein angles were associated with decreased indexed cardiac output, lower tissue Doppler velocities, higher right-sided Tei indices, and severe tricuspid regurgitation. Umbilical arterial lengthening occurs in 52% of recipients and is associated with abnormal Doppler flows, low systolic tissue Doppler velocities, reduced cardiac output, and elevated markers of cardiac failure. This may reflect chronicity and severity of hypertension in the recipient fetus. Further research is needed to explore the mechanisms of elongation and long-term implications.

The impact of laser surgery on angiogenic and anti-angiogenic factors in twin–twin transfusion syndrome: a prospective study*

Objective: To examine the effect of laser surgery on angiogenic and anti-angiogenic factors in patients with twin–twin transfusion syndrome (TTTS). Methods: Cases of TTTS and uncomplicated monochorionic diamniotic twin pregnancies between 16 and 26 weeks’ gestation were prospectively enrolled into the study. Maternal blood samples were obtained to measure angiogenic factors (vascular endothelial growth factor-A [VEGF], placental-derived growth factor [PlGF], and endothelin) and anti-angiogenic factors (soluble fms-like tyrosine kinase (sFlt-1), soluble endoglin (sEng), and sFlt-1/PlGF ratio). For cases, these factors were measured at visit 1 (pre-operatively), visit 2 (postoperative day one), and visit 3 (at least 3 weeks after surgery). In controls, the factors were measured at visit 1 (enrollment) and visit 2 (at least 3 weeks later). Levels of angiogenic and anti-angiogenic factors between cases and controls were compared. Results: At enrollment, the TTTS cases demonstrated an anti-angiogenic state with significantly higher sFlt-1, sEng, sFlt-1/PlGF ratio, and lower PlGF. Laser surgery, comparing visit 1–3, had a partial corrective effect on TTTS cases. sFlt-1 significantly decreased several weeks after surgery. The other factors (PlGF, endothelin, sFlt-1, sEng, and sFlt-1/PlGF ratio) were not statistically significantly different by visit 3. Conclusion: Laser surgery partially corrected the angiogenic profile in patients with TTTS.

Fetal cardiac parameters for prediction of twin-to-twin transfusion syndrome.

To assess myocardial performance index measured by conventional Doppler (MPI) and by tissue Doppler imaging (MPI') at 18 weeks' gestation in monochorionic diamniotic twins for the prediction of twin-to-twin transfusion syndrome (TTTS). This was a single-center observational study of 100 uncomplicated monochorionic diamniotic twin pregnancies attending the twin pregnancy clinic at the University Hospital Spedali Civili of Brescia from 2009 to 2012. MPI and MPI' were obtained from the left (LV) and right (RV) ventricles of each twin at around 18 weeks of gestation (range, 17 + 1 to 19 + 4 weeks) and fortnightly thereafter. Cases which later developed TTTS formed the study group, and the remaining controls were subdivided into those continuing as uncomplicated pregnancies and those which later developed selective intrauterine growth restriction (sIUGR). Data were analyzed by receiver-operating characteristics curve analysis and univariate and multivariable logistic regression. Of the 100 pregnancies, 88 were controls (84 uncomplicated and four developed sIUGR) and 12 developed TTTS. RV-MPI and LV-MPI, and LV-MPI' were significantly higher in future TTTS recipients than in controls, while RV-MPI' was significantly lower in donors. RV-MPI and LV-MPI and LV-MPI' were found to be predictive indicators in pregnancies that had not yet developed TTTS. Their negative predictive values were > 90%, and their specificities > 80%. The best performing index was LV-MPI', with a sensitivity of 91.7% and specificity of 88.6%. Before diagnosis of TTTS, the cardiac function (as assessed by MPI and MPI') of the future donor twin is not grossly abnormal, but that of the recipient is abnormal. We identified cardiac indices predictive of the subsequent development of TTTS, and suggest a possible role of these indices in planning the follow-up of monochorionic diamniotic twin pregnancies.

P19.01: Fetal hemodynamic parameters in monochorionic diamniotic twin pregnancies complicated with twin–twin transfusion syndrome treated by laser photocoagulation

To determine the prognostic value of fetal echocardiography for twin-twin transfusion syndrome (TTTS) using the CHOP (Children's Hospital of Philadelphia) cardiovascular score in correlation with the Quintero staging. To evaluate whether hemodynamic changes, pre and post laser photocoagulation, predict the neonatal survival. Hemodynamic parameters of 90 pregnancies with TTTS were collected pre and post laser photocoagulation. The cardiac function parameters were compared to 90 uncomplicated monochorionic diamniotic twin pregnancies. Between 2006 and 2013, 90 laser photocoagulations were performed. Quintero staging was divided between stage 1 (11%), 2 (39%), 3 (49%) and 4 (1%). Fetal echocardiography was available in 82 cases but pre and post laser intervention in only 69 cases. Neonatal survival rates were 19%, 22% and 59% for zero, one or two twins respectively. At least one twin was delivered alive in 81% of the pregnancies. The mean gestational age at surgery was 20 weeks (range 15-25). The mean age at birth in cases with at least one live birth was 32 weeks (range 24-38). The following factors were not associated with neonatal survival: placental location, Quintero staging, gestational age at diagnosis, amnioreduction volume. The preoperative myocardial performance index (MPI) was higher in the recipient than in the donor twin (0.58 vs 0.37, p < 0.001). In healthy monochorionic twins MPI was 0.43 (right ventricle) and 0.37 (left ventricle), and the CHOP cardiovascular score was 1.8. The mean CHOP score was 4.8 preoperatively and 3.3 postoperatively (p <0.001, paired t test). The CHOP score was not related to neonatal survival. Our study confirmed a correlation between the Quintero staging and the CHOP cardiovascular score. However, both tests showed no prognostic value in predicting neonatal survival rates. Discrepancies in hemodynamic parameters between TTTS and controls and between donor and recipient twin are evidenced by fetal echocardiography.

Placental characteristics in uncomplicated monochorionic diamniotic twin pregnancies

Objective To investigate the association between placental sharing,vascular anastomoses,cord insertion and perinatal outcome in uncomplicated monochorionic diamniotic (MCDA) placentas.Methods Between January 1,2012 and July 31,2013,60 uncomplicated (seclective fetal growth restriction,twin anemia-polycythemia sequence and twin-twin transfusion dyndrome) MCDA placentas were studied.These uncomplicated MCDA placentas were divided into the placenta equally shared group with placental territory discordance (PTD) ＜0.25 and the placenta unequally shared group with PTD ≥ 0.25.Angioarchitecture,cord insertion type and the distance between two cord insertions were compared using the Chi-square test and nonparametric test.Results Mean maternal age was (30.3±4.1) years.There were 39 cases (65％) in the placenta equally shared group and 21 (35％) in the placenta unequally shared group.Vascular anastomoses were observed in all placentas,arterioarterial anastomoses in 58 placentas (97％),and venovenous anastomoses in 17 placentas (28％).The overall diameter and the maximum diameter of arterioarterial anastomoses in the placenta equally shared group were (0.19±0.11) cm and (0.18±0.09) cm,respectively,and were lower than those in the placenta unequally shared group [(0.27±0.11) cm and (0.27±0.12) cm,respectively] (T were-2.39 and-2.94,P＜0.05,respectively).No significant differences in the number,the overall diameter and the maximum diameter of venovenous anastomoses were observed between the two groups (all P＞0.05).The incidence of cord velamentous insertion and cord velamentous insertion plus cord marginal insertion were 14％ (11/78) and 42％ (33/78),respectively,in the placenta equally shared group,and were similar to those in the placenta unequally shared group [14％ (6/42) and 33％ (14/42),x2 were 1.00 and 0.43,P＞0.05,respectively].The mean distance between two cord insertions was shorter in the placenta unequally shared group than in the placenta equally shared group [(14.3±6.3) cm vs (18.2±6.0) cm,T=2.37,P＜0.05].Conclusions In cases with unequally shared placenta,the distance between two cord insertions is shorter and the diameter of arterioarterial anastomoses is larger,which may compensate for their unequal placental territories,leading to no complications in these MCDA twin. Key words: Twin, monochorionic; Placental circulation; Umbilical arteries; Umbilical veins

Predominantly placenta‐expressed mRNAs in maternal plasma as predictive markers for twin–twin transfusion syndrome

This study aimed to identify a set of predominantly placental (PP) mRNAs, which are associated with later-developing twin-to-twin transfusion syndrome (TTTS). First, out of 50 PP mRNAs we previously reported, we select target mRNAs that are ordinarily detectable in maternal plasma. Plasma concentrations of these PP mRNAs were measured in monochorionic diamniotic twin (MCDA-T) pregnancies complicated by TTTS later (n = 11) and in uncomplicated MCDA-T pregnancies (n = 17). Finally, the diagnostic values of the PP mRNAs in plasma were evaluated. From 50 PP mRNAs, nine [human placental lactogen (hPL); pregnancy-specific glycoproteins 2 (PSG2); human pregnancy-specific glycoproteins 3 (PSG3); syncytin; syncytin 2; retinoic acid-induced 14; A disintegrin and metalloproteinase domain-containing protein 12 (ADAM12); chorionic glycoprotein hormones, alpha polypeptide; and chorionic glycoprotein hormones, and beta polypeptide] were selected as target mRNAs. Changes in six PP mRNAs [increased hPL, PSG2, and PSG3 and decreased syncytin, syncytin2, and ADAM12] in maternal plasma were detected in MCDA-T pregnant women who subsequently developed TTTS. Finally, mRNA signatures gave elevated AUCs (hPL/PSG2: 0.8717; hPL/PSG3: 0.8449; hPL/ADAM12: 0.8396) compared with single hPL mRNA. Quantitative aberration of plural cell-free PP mRNAs in maternal plasma precedes the appearance of clinically apparent TTTS. This suggests that pathophysiological changes in the placenta are associated with morbid conditions of TTTS.

Increased Stillbirth in Uncomplicated Monochorionic Twin Pregnancies

To estimate the risk of stillbirth in apparently uncomplicated monochorionic-diamniotic twin pregnancies by systematic review and meta-analysis and compare it with that in uncomplicated dichorionic pregnancies. We performed an electronic search (January 1985 to April 2012) of Medline, PubMed, Embase, and ClinicalTrials.gov databases. Studies detailing gestational-age specific stillbirth rates after 24 weeks of gestation in monochorionic-diamniotic twin pregnancies uncomplicated by twin-twin transfusion syndrome, growth restriction, or major anomalies. The rate and risk of stillbirth were calculated in 2-week gestational age blocks and compared in controlled studies with dichorionic pregnancies. We evaluated 361 studies to include nine informative studies, four after additional data from the investigators. The rate of stillbirth per 1,000 uncomplicated monochorionic-diamniotic pregnancies at 32-33, 34-35, and 36-37 weeks of gestation was 5.1, 6.8, and 6.2, respectively. The risk of stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 1.6%, 1.3% and 0.9%, respectively. Compared with uncomplicated dichorionic pregnancies, the odds ratio for stillbirth per pregnancy at 32, 34, and 36 weeks of gestation was 4.2 (95% confidence interval [CI] 1.4-12.6), 3.7 (CI 1.1-12.0), and 8.5 (CI 1.6-44.7), respectively. Uncomplicated monochorionic twin pregnancies are at substantial risk of stillbirth throughout the third trimester, which is severalfold higher than in dichorionic twin pregnancies. Given the risk of fetal death to the cotwin, these data should inform decisions around timing of delivery in seemingly normal monochorionic twin pregnancies.

Timing of planned delivery in uncomplicated monochorionic diamniotic twin pregnancies: a review of the literature

Monochorionic diamniotic (MCDA) twins comprise of 20–30% of twin pregnancies; roughly 50% will be undelivered and ‘uncomplicated’ beyond 32 weeks gestation. This review details accumulating data regarding the risk of intrauterine fetal demise (IUFD) in ‘uncomplicated’ MCDA twins and risks associated with prematurity. ‘Uncomplicated’ MCDA twins are at increased risk for IUFD, even when under intensified surveillance in tertiary care centers. The prospective risk of IUFD in uncomplicated MCDA varies among different studies, with reported rates of up to 3.3% at 34 weeks and 2.2% at 36 weeks. If single IUFD occurs, it exposes the surviving co-twin to potential significant morbidity and mortality. It had been suggested that elective preterm delivery would eliminate this risk, but recent evidence of prematurity morbidity are accumulating. With more intensified monitoring from 32 weeks, it is possible that the rate of IUFD is lower than anticipated. We reviewed the data regarding these risks and their contribution to the decision-making process.

Effectiveness of timing strategies for delivery of monochorionic diamniotic twins

The purpose of this study was to compare strategies for delivery timing of uncomplicated monochorionic diamniotic twin pregnancies. A decision tree compared 9 strategies that included scheduled delivery between 32 and 38 weeks' gestation, with or without confirmation of fetal lung maturity. Outcomes in the model included fetal death, infant death, respiratory distress syndrome, mental retardation, and cerebral palsy. A scheduled delivery at 38 weeks' gestation was the preferred strategy, which resulted in the highest quality adjusted life years under base-case assumptions. Decreased, but comparable, quality adjusted life years estimates resulted from scheduled deliveries at 36 and 37 weeks' gestation, with or without amniocentesis. Sensitivity analyses demonstrated that the optimal gestational age for delivery was always ≥36 weeks' gestation. This decision analysis suggests that, for women with uncomplicated monochorionic twins, delivery between 36 and 38 weeks' gestation is the preferred strategy for timing of delivery.

170: Timing of delivery in uncomplicated monochorionic-diamniotic twin pregnancies: comparison of neonatal outcomes at late preterm gestational ages

The optimal time to deliver uncomplicated monochorionic-diamniotic (MCDA) twins remains uncertain. We compared neonatal outcomes of uncomplicated MCDA twins electively delivered at different late preterm gestational ages.

Prospective risk of fetal death in uncomplicated monochorionic twins

A retrospective cohort study was carried out in a university teaching hospital to determine the prospective risk of unexpected fetal death in uncomplicated monochorionic diamniotic (MCDA) twin pregnancies after viability. All MCDA twins delivered at or after 24 weeks' gestation from July 1999 to July 2007 were included. Pregnancies with twin-twin transfusion syndrome, growth restriction, structural abnormalities, or twin reversed arterial perfusion sequence were excluded. Of the 144 MCDA twin pregnancies included in our analysis, the risk of intrauterine death was 4.9%. The prospective risk of unexpected intrauterine death was 1 in 43 after 32 weeks' gestation and 1 in 37 after 34 weeks' gestation. Our results demonstrate that despite close surveillance, the unexpected intrauterine death rate in uncomplicated MCDA twin pregnancies is high. This rate seems to increase after 34 weeks' gestation, suggesting that a policy of elective preterm delivery warrants evaluation.

High Risk of Unexpected Late Fetal Death in Monochorionic Twins Despite Intensive Ultrasound Surveillance: A Cohort Study

BackgroundThe rationale for fetal surveillance in monochorionic twin pregnancies is timely intervention to prevent the increased fetal/perinatal morbidity and mortality attributed to twin–twin transfusion syndrome and intrauterine growth restriction. We investigated the residual risk of fetal death after viability in otherwise uncomplicated monochorionic diamniotic twin pregnancies.Methods and FindingsWe searched an electronic database of 480 completed monochorionic pregnancies that underwent fortnightly ultrasound surveillance in our tertiary referral fetal medicine service between 1992 and 2004. After excluding pregnancies with twin–twin transfusion syndrome, growth restriction, structural abnormalities, or twin reversed arterial perfusion sequence, and monoamniotic and high-order multiple pregnancies, we identified 151 uncomplicated monochorionic diamniotic twin pregnancies with normal growth, normal liquor volume, and normal Doppler studies on fortnightly ultrasound scans. Ten unexpected intrauterine deaths occurred in seven (4.6%) of 151 previously uncomplicated monochorionic diamniotic pregnancies, within 2 wk of a normal scan, at a median gestational age of 34+1 wk (weeks+days; range 28+0 to 36+3). Two of the five cases that underwent autopsy had features suggestive of acute late onset twin–twin transfusion syndrome, but no antenatal indicators of transfusional imbalance or growth restriction, either empirically or in a 1:3 gestation-matched case–control comparison. The prospective risk of unexpected antepartum stillbirth after 32 wk was 1/23 monochorionic diamniotic pregnancies (95% confidence interval 1/11 to 1/63).ConclusionDespite intensive fetal surveillance, structurally normal monochorionic diamniotic twin pregnancies without TTTS or IUGR are complicated by a high rate of unexpected intrauterine death. This prospective risk of fetal death in otherwise uncomplicated monochorionic diamniotic pregnancies after 32 wk of gestation might be obviated by a policy of elective preterm delivery, which now warrants evaluation.

Abundant vascular anastomoses in monoamniotic versus diamniotic monochorionic placentas

OBJECTIVE: The study’s aim was to compare the vascular anatomy of monoamniotic with uncomplicated diamniotic monochorionic pregnancies. STUDY DESIGN: The fetoplacental circulations of both twins in 18 monochorionic placentas were perfused after delivery under optimal physiologic conditions, and anastomoses were delineated by dye-contrast injection. Six were from pregnancies with monochorionic monoamniotic twins and 12 from uncomplicated monochorionic diamniotic twin pregnancies. RESULTS: The cord insertions in monochorionic monoamniotic placentas were central, with a median intercord distance of 3.2 cm (range 1.7 to 6.9 cm), whereas in monochorionic diamniotic control placentas the cord insertions ( n = 24) were rarely central (marginal, 13; velamentous, 2) or eccentric (6), with a mean intercord distance of 9.6 cm (5.2 to 16.7; P < .001). Cord entanglement was present in 5 of 6 cases of monochorionic monoamniotic placentas and in none of the monochorionic diamniotic placentas. Monochorionic monoamniotic placentas had more anastomoses than did monochorionic diamniotic placentas, both overall (median 13 vs 5 respectively, P < .01) and for each of the different types (arterioarterial, venovenous, and arteriovenous, P < .01). CONCLUSIONS: Monoamniotic monochorionic placentas have significantly greater numbers of both superficial and deep anastomoses than do uncomplicated monochorionic diamniotic pregnancies. This observation suggests a vascular basis for the extreme rarity of twin-twin transfusion syndrome in monoamniotic pregnancies. (Am J Obstet Gynecol 1998;179:788-93.)