Hepatic arterial buffer response in monochorionic twins with selective fetal growth restriction.

OBJECTIVES: Monochorionic twins (MC) have higher risk of perinatal morbi-mortality compared to singletons and dichorionic twins (DC). Selective fetal growth restriction (sFGR) increases the chances of adverse outcome. Hepatic arterial buffer response (HABR) is an important mechanism for maintaining liver perfusion. We hypothesised that HABR is active in monochorionic diamniotic twins (MCDA) with sFGR where restricted fetus may have liver hypoperfusion. The objective of this study is to test whether the HAV-ratio is diminished in pregnancies affected by selective fetal growth restriction pointing to activation of HABR in the growth-restricted fetus. METHODS: sFGR was defined according to a consensus definition. Hepatic artery (HA) peak systolic velocity (PSV) was measured and its correlation with fetal Dopplers and pregnancy characteristics were determined. A ratio using HA-PSV (HAV-ratio) was calculated and its association with sFGR was established. Further analysis of HA-PSV was performed comparing z-scores between normal and growth restricted fetuses. RESULTS: We included 202 MCDA pregnancies, 160 (79 %) normal and 42 (21 %) with sFGR. HAV-ratio was significant different between groups. The mean HAV-ratio was 1.01 (±0.20) for normal twins and 0.77 (±0.25) for sFGR. Furthermore, HA-PSV z-scores was significant increased in in growth-restricted fetus (0.94±1.45), while in normal fetuses was -0.16 (±0.97). CONCLUSIONS: Our findings demonstrate that, in pregnancies with sFGR, HAV-ratio is significantly lower than in normal MCDA pregnancies. The lower HAV-ratio is due to an increase in HA PSV in the growth restricted fetus. This observation indicates an activation of HABR in the small fetus.

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.

Predictive value of maternal serum placental growth factor levels for discordant fetal growth in twins: a retrospective cohort study.

BACKGROUND: Accurate prenatal recognition of discordant fetal growth in twins is critical for deciding suitable management strategies. We explored the predictive value of the level of maternal second-trimester placental growth factor (PLGF) as a novel indicator of discordant fetal growth. METHODS: A total of 860 women pregnant with twins were enrolled, including 168 women with monochorionic twins (31 cases of discordant fetal growth and 137 without) and 692 with dichorionic twins (79 cases of discordant fetal growth and 613 without). Maternal second-trimester PLGF concentrations were measured via immunofluorescence. RESULTS: Maternal second-trimester PLGF levels were significantly lower in women pregnant with twins who subsequently developed discordant fetal growth than in those who did not (monochorionic twin pregnancy: P < 0.001; dichorionic twin pregnancy: P < 0.001). A 3-4 fold difference in median PLGF concentrations was detected between the two groups with both monochorionic and dichorionic twin pregnancies. Maternal second-trimester PLGF levels were significantly correlated with birth weight differences (monochorionic twin pregnancy: r = - 0.331, P < 0.001; dichorionic twin pregnancy: r = - 0.234, P < 0.001). A receiver operating characteristic curve was used to evaluate the predictive efficiency. In monochorionic twin pregnancies, the area under the curve (AUC) was 0.751 (95% confidence interval [CI]: 0.649-0.852), and the cutoff value was 187.5 pg/mL with a sensitivity of 77.4% and specificity of 71.0%. In dichorionic twin pregnancies, the AUC was 0.716 (95% CI; 0.655-0.777), and the cutoff value was 252.5 pg/mL with a sensitivity of 65.1% and specificity of 69.6%. Based on the above cutoff values, univariate and multivariate logistic regression analyses were performed to calculate the odds ratios (OR) for the PLGF levels. After adjustment for potential confounding factors, low PLGF concentrations still significantly increased the risk of discordant fetal growth (monochorionic twin pregnancy: adjusted OR: 7.039, 95% CI: 2.798-17.710, P < 0.001; dichorionic twin pregnancy: adjusted OR: 4.279, 95% CI: 2.572-7.120, P < 0.001). CONCLUSIONS: A low maternal second-trimester PLGF level is considered a remarkable risk factor and potential predictor of discordant fetal growth. This finding provides a complementary screening strategy for the prediction of discordant fetal growth and offers a unique perspective for the subsequent research in this field.

Longitudinal maternal hemodynamic evaluation in uncomplicated twin pregnancies according to chorionicity: physiological cardiovascular dysfunction in monochorionic twin pregnancy.

OBJECTIVE: Maternal cardiac function plays a crucial role in placental function and development. The maternal hemodynamic changes in twin pregnancy are more pronounced than those in singleton pregnancy, presumably due to a greater plasma volume expansion. In view of the correlation between maternal cardiac and placental function, it is plausible that chorionicity could influence maternal cardiac function. The aim of this study was to compare the longitudinal maternal hemodynamic changes between uncomplicated dichorionic (DC) and monochorionic (MC) twin pregnancies and in comparison to singleton pregnancies. METHODS: Included in the study were 40 MC diamniotic and 35 DC diamniotic uncomplicated twin pregnancies. These were compared with a group of 294 healthy singleton pregnancies from a previous cross-sectional study. All participants underwent a hemodynamic evaluation using an Ultrasound Cardiac Output Monitor (USCOM®), at three different stages in pregnancy (11-15 weeks, 20-24 weeks and 29-33 weeks). The following parameters were recorded: mean arterial pressure (MAP), stroke volume (SV), stroke volume index (SVI), heart rate, cardiac output (CO), cardiac index (CI), systemic vascular resistance (SVR), systemic vascular resistance index (SVRI), stroke volume variation, Smith-Madigan inotropy index (INO) and potential-to-kinetic-energy ratio (PKR). RESULTS: In the first trimester, DC and MC twin pregnancies showed lower MAP, SVR and PKR and higher CO and SV in comparison to singleton pregnancy. In the second trimester, maternal CO (8.33 vs 7.30 L/min, P = 0.03) and CI (4.52 vs 4.00 L/min/m2 , P = 0.02) were significantly higher in MC compared with DC twin pregnancy. In the third trimester, compared with in singleton pregnancy, women with MC twin pregnancy showed significantly higher PKR (24.06 vs 20.13, P = 0.03) and SVRI (1837.20 vs 1698.48 dynes × s/cm5 /m2 , P = 0.03), and significantly lower SV (78.80 vs 88.80 mL, P = 0.01), SVI (42.79 vs 50.31 mL/m2 , P < 0.01) and INO (1.70 vs 1.87 W/m2 , P = 0.03); these differences were not observed between DC twin and singleton pregnancies. CONCLUSIONS: Maternal cardiovascular function undergoes significant change during uncomplicated twin pregnancy and chorionicity influences maternal hemodynamics. In both MC and DC twin pregnancy, hemodynamic changes are detectable as early as the first trimester, showing higher maternal CO and lower SVR compared with singleton pregnancy. In DC twin pregnancy, the maternal hemodynamics remain stable during the rest of pregnancy. In contrast, in MC twin pregnancy, the rise in maternal CO continues in the second trimester in order to sustain the greater placental growth. There is a subsequent crossover, with a reduction in cardiovascular performance during the third trimester. © 2023 International Society of Ultrasound in Obstetrics and Gynecology.

Hepatic arterial buffer response: activation in donor fetuses and the effect of laser ablation of intertwin anastomosis.

OBJECTIVES: Hepatic arterial buffer response (HABR) is an important defence mechanism for maintaining liver blood flow. It is suspected that HABR is active in monochorionic diamniotic twins (MCDA) with twin-to-twin transfusion syndrome (TTTS) where donor compensates a setting of volume depletion and the recipient an overload. The present study investigates whether in TTTS, HABR is active in donor and/or recipient individually and try to determine if the activation of HABR is a direct response to TTTS. METHODS: Hepatic artery (HA) peak systolic velocity (PSV) was measured in normal MCDA fetuses and TTTS. Correlation with relevant fetal Dopplers and characteristics were determined. Z-scores for HA-PSV (HAV-Z) were calculated and its association with TTTS in donors and recipients were determined as well as changes in HAV-Z after laser treatment. RESULTS: In this study 118 MCDA were included, 61.9 % normal and 38.1 % TTTS. Of the TTTS 22 required laser treatment. A total of 382 scans were performed in normal group and 155 in TTTS. Our data demonstrates that in donors HAV-Z was 2.4 Z-scores higher compared to normal fetuses (ß=2.429 95 % CI 1.887, 2.971; p<0.001) and after laser treatment HAV-Z reduced (ß=-1.829 95 % CI -2.593, -1.064; p<0.001). There was no significant difference between recipients and normal (ß=-0.092 95 % CI -0.633, 0.449; p=0.738). CONCLUSIONS: HABR is active in TTTS, promoting an increased hepatic blood flow in donors. The activation is direct response to TTTS as shown by the reduction in HAV-Z after laser. This finding provides important insights into the pathophysiology of TTTS.

"The Strange Case of Dr Pump and Mr Acardiac": The Twin Reversed Arterial Perfusion (TRAP) Sequence in Two Monochorionic Monoamniotic (MCMA) Twin Pregnancies-Diagnosis, Prognosis and Management: Review of Literature.

The Twin Reversed Arterial Perfusion (TRAP) Sequence is an extremely rare complication of monochorionic twin pregnancies, with one severely malformed twin (the "acardiac") lacking autonomous placental blood supply and being perfused by the co-twin (the "pump"), through arterio-arterial (and sometimes also veno-venous) vascular anastomoses located on the placental surface. The prognosis is poor: mortality is 100% in the acardiac twin because of its severe malformations and about 50-55% in the pump twin, mainly due to heart failure and prematurity. So, the goal of perinatal management of the TRAP twin pregnancy is to deliver a healthy and near-term pump twin without heart failure or fetal hydrops. Intuitively, the earlier the diagnosis, the better the outcome. Herein, we report two cases of monochorionic monoamniotic (MCMA) twin pregnancies complicated by the TRAP Sequence, which are of interest since the objective of early diagnosis was achieved by means of transvaginal and 3D ultrasound, two techniques which revealed themselves as being useful to this purpose but are underused in the literature. The second aim of this study is to provide an overview of literature data about the diagnosis, prognosis establishment, and management of this rare condition, which are still debated and unclear due to negligible poor-quality evidence.

The Management of Acardiac Twinning: Twin Reverse Arterial Perfusion Sequence - An International Survey.

INTRODUCTION: The optimal approach and therapy method for the acardiac twin with a reverse arterial perfusion sequence has not yet been established. The aim of this study was to determine the clinical practice patterns among international fetal therapy units in their management of these cases. METHODS: A survey was sent to fetal centers across the world via email between December 2020 and December 2021. RESULTS: Responses were obtained from 77% contacted centers. The most frequent ultrasound variables used in the evaluation of twin reverse arterial perfusion sequence include echocardiographic assessment of the pump twin and umbilical artery Doppler waveforms in the acardiac and pump twins, in 90% and 80% of the centers, respectively. Most centers in Europe and Latin America propose an in utero intervention in all cases. Most centers in Europe and Latin America prefer interstitial laser ablation, whereas radiofrequency ablation (RFA) is preferred in North America. The earliest gestational age for an intervention is on mean 13 weeks in Europe, which is earlier than the other geographic areas (p = 0.001). CONCLUSIONS: Most centers agreed that antenatal evaluation should include echocardiography along with the UA Doppler waveform measurements, and the most frequently used interventions were interstitial laser ablation or RFA at a median between 14 and 26 weeks.

Retrospective comparison of monochorionic diamniotic twin pregnancies stratified by spontaneous or artificial conception.

OBJECTIVES: To compare outcomes of monochorionic diamniotic (MCDA) twin pregnancies by in vitro fertilization (IVF) vs. spontaneously conceived counterparts. METHODS: Retrospective comparison. Data about MCDA twin pregnancies, conceived spontaneously or by IVF, attending the Twin Pregnancy Care Unit of Sant'Anna Hospital in Turin (Italy) between January 1st 2010 and March 31st 2022, were collected retrospectively. Obstetric, fetal, and neonatal outcomes of MCDA twin pregnancies by IVF were compared to those of spontaneously conceived counterparts. Data were described by univariate and multivariate analysis. RESULTS: 541 MCDA twin pregnancies were included in the study, among which 45 conceived by IVF and 496 spontaneously conceived. Women with IVF twins were older than those who conceived spontaneously (36.7 ± 5.7 vs. 32.1 ± 5.2 years; p<0.001). No significant difference in the prevalence of pregnancy complications between the two groups was found, except for an increased incidence of hypertensive disorders among IVF pregnancies (17.8 vs. 8.5 %; p=0.039), which resulted nonsignificant after adjusting for maternal age and parity (aOR 1.9, 95 % CI 0.8-4.6). Data about 1,046 live born babies (90 conceived by IVF and 956 spontaneously) were also collected: perinatal outcomes did not differ between the two groups. CONCLUSIONS: Our results suggest that MCDA twin pregnancies following IVF are not at increased risk of adverse outcomes compared to spontaneous MCDA twin pregnancies.

Congenital heart defects in monochorionic twin pregnancy complicated by selective fetal growth restriction.

OBJECTIVES: To evaluate the prevalence, subtypes and postnatal outcomes of congenital heart defects (CHD) in a cohort of monochorionic diamniotic (MCDA) twin pregnancies complicated by selective fetal growth restriction (sFGR), and to compare this population with a cohort of uncomplicated MCDA pregnancies evaluated during the same period. METHODS: This was a retrospective analysis of all consecutive MCDA pregnancies referred between 2009 and 2018, including those complicated by sFGR (Group A) and those without complications (Group B). All neonates delivered in our center were screened for CHD before discharge. Discharge letters for all those delivered elsewhere were retrieved. Pregnancies with complications other than sFGR and those without perinatal follow-up were excluded. Pregnancies in Group A were divided into three types according to the Gratacós system of sFGR classification. RESULTS: A total of 870 MCDA twin pregnancies were included: 296 in Group A and 574 in Group B. In Group A, the prevalence of CHD was 3.7% (22/592 twins), with no significant difference in CHD frequency between the three types of sFGR (Type I, 3.7%; Type II, 3.2%; Type III, 4.2%; P = 0.55). Of four Type-III sFGR pregnancies with CHD, one had pulmonary stenosis (PS) in the larger twin and isolated coarctation of the aorta in the smaller cotwin, and three had PS in the larger twin only. No Type-III sFGR pregnancies in which only the smaller twin was affected by CHD were observed. Of 11 CHD cases in the larger twin, 10 (91%) were right ventricular outflow tract abnormalities (RVOTA), and one (9%) was a ventricular septal defect. In the smaller twins, 11 cases of CHD were observed, covering a broad spectrum of cardiac abnormalities. In Group B, the CHD prevalence was 1.1% (13/1148 twins), which was similar to that in the general population, according to the EUROCAT registry for the same period and geographical area of the study (0.96%; P = 0.579). The CHD prevalence was significantly higher in Group A compared with Group B (3.7% vs 1.1%; P = 0.0002; odds ratio, 3.57 (95% CI, 1.78-7.22)). In all pregnancies with CHD in the study population, the anomaly was discordant. CONCLUSIONS: In MCDA twin pregnancy, sFGR was associated with a three-fold higher prevalence of CHD. Women with such pregnancies should be referred to a tertiary care hospital for pre- and postnatal cardiac evaluation, treatment and long-term follow-up. In larger twins, the only major CHD observed was RVOTA, while a broad spectrum of CHD was noted in smaller twins. The higher risk of CHD in MCDA pregnancies appears to be due to the typical complications of the monochorionic pregnancy, rather than to the monochorionic nature of the pregnancy itself. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Hepatic arterial buffer response in monochorionic diamniotic pregnancies with twin-to-twin transfusion syndrome.

OBJECTIVES: Hepatic arterial buffer response (HABR) is an important regulatory process for hepatic blood flow. Its activity has been described in some fetal adverse conditions but in twin-to-twin transfusion syndrome (TTTS) it is unknown if such response is present. The aim of this study is to test the hypothesis that HABR operates in monochorionic diamniotic twins (MCDA) with TTTS. METHODS: Hepatic artery pulsatility index (PI) and peak systolic velocity (PSV) were measured prospectively in 64 MCDA pregnancies. 43 without TTTS (group 1) and in 21 pregnancies with TTTS (group 2). We calculated ratios for PI (HAPI-ratio) and PSV (HAV-ratio) between recipient and donor in group 2 or bigger and smaller fetus in group 1 and compared groups. The association of HAV-ratio and HAPI ratio with TTTS, relation with other fetal Dopplers and reliability of measurement by a single operator were investigated. RESULTS: HAV-ratio and HAPI-ratio appears to be independent from fetal Dopplers, estimated weight and gestational age. In group 2, HAV-ratio is lower than group 1 (p<0.001, 95% CI 0.443-0.643). In group 1 the mean HAV-ratio is 1.014 (±0.021) while in group 2 is 0.47 (±0.035). HAPI-ratio is lower in group 2 than in group 1 although this difference was not significant (p=0.066, 95% CI -0.007-0.231). A good reliability of measurements of hepatic artery PSV and PI was demonstrated by intraclass correlation coefficient analysis (ICC 0.971 95% CI 0.963-0.977, p<0.001 and ICC 0.694 95% CI 0.596-0.772, p<0.001, respectively). CONCLUSIONS: Monochorionic pregnancies with TTTS are associated with lower HAV-ratios. This could be explained by an active HABR.

Ultrasound assessment of twin reversed arterial perfusion sequence for the prediction of adverse pregnancy outcomes in the first trimester.

OBJECTIVE: To investigate twin reversed arterial perfusion (TRAP) sequence for the prediction of TRAP-related adverse pregnancy outcomes at the gestational age of 11-14 weeks. METHODS: Pregnant women in the first trimester diagnosed with TRAP were recruited at West China Second University Hospital from January 2015 to June 2018. Systematic screening for the pump twin's crown-rump length (CRL) and acardiac twin's upper pole-rump length (URL) was conducted using ultrasonic detection. The (CRL - URL)/CRL and URL/CRL ratios were used to assess the pregnancy outcomes for the pump twin. Twenty-one pregnant women aged 21-39 years with a gestation of 11-14 weeks were recruited. RESULTS: TRAP was diagnosed on average (± standard deviation (SD)) at pregnancy week 13.1 ± 0.18. The pump twins' mean (± SD) CRL was 6.65 ± 1.1 cm. The incidence of intrauterine death for the pump twins was 19.0% (n = 4), the miscarriage rate was 14.3% (n = 3), and the live birth rate was 66.7% (n = 14). The (CRL - URL)/CRL ratios between the nonsurvival (intrauterine death and miscarriage) and survival groups significantly differed (0.33 ± 0.08 vs. 0.58 ± 0.08, p < 0.05). Similarly, the URL/CRL ratios between the nonsurvival and survival groups significantly differed (0.67 ± 0.08 vs. 0.42 ± 0.08, p < 0.05). CONCLUSION: The (CRL - URL)/CRL and URL/CRL ratios were valuable indicators for determining pregnancy outcomes of pump twins with TRAP at an early gestational age.

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.

Long-term follow-up of complicated monochorionic twin pregnancies: Focus on neurodevelopment.

Monochorionic twin pregnancies have an increased risk of morbidity and mortality. Due to the advancements in screening and treatment strategies, mortality rates have decreased. Improving survival rates demands a shift in scope toward long-term outcomes. In this review, we focus on neurodevelopmental outcome in survivors from complicated monochorionic twin pregnancies, including twin-twin transfusion syndrome (TTTS), twin anemia-polycythemia sequence (TAPS), acute peripartum TTTS, acute perimortem TTTS, selective fetal growth restriction (sFGR) and monoamnionicity. Our aim is to provide an overview of the current knowledge on the long-term outcome in survivors, including psychomotor development and quality of life, and provide recommendations for future research and follow-up programs.

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.

How to Better Distinguish between Type II and III Selective Fetal Growth Restriction in Monochorionic Twin Pregnancies?

OBJECTIVES: The objective of this study is to determine additional variables, next to umbilical artery (UA) Doppler, to help differentiate between Type II and III selective fetal growth restriction (sFGR). METHODS: Retrospective analysis categorizing monochorionic diamniotic twin pregnancies with sFGR and abnormal UA Doppler as either Type II or III sFGR based on the diameter of the artery-to-artery (AA) anastomosis of ≤2 or >2 mm, respectively on placental examination after birth. This exploratory study compared maternal characteristics, pregnancy outcome, placental characteristics, and ultrasound features between the two groups. RESULTS: We included 40 sFGR placentas, 13 were classified as Type II and 27 as Type III. Maternal age was higher in Type II. Small Type II twins had lower birth weights (BWs) for gestational age and BW discordance was higher in Type II. Type III placentas were more unevenly divided, but Type III pairs differed less in BW than expected relative to their placental discordance. Type III placentas more commonly had a vein-to-vein anastomosis and larger artery-to-vein anastomoses than Type II placentas, and proximate cord insertions were only observed in Type III. On the ultrasound scan at first diagnosis, small Type II twins were more growth-restricted. An AA anastomosis was detected in half of the Type III cases and in none of the Type II group. Signs of high-output cardiac strain were observed only in large Type III twins. In contrast, placental dichotomy was detected in nearly half of the Type II cases and only one Type III case. CONCLUSIONS: The presence of an AA anastomosis, signs of cardiac strain in the large twin, and proximate cord insertions suggested Type III sFGR, whereas placental dichotomy and a severe growth restriction were typically present in Type II. Prospective studies need to validate if these markers help prenatal differentiation between Type II and III sFGR.

Umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy: association with placental sharing and fetal demise.

OBJECTIVE: To examine the association of umbilical venous diameter and flow in monochorionic diamniotic twin pregnancy with placental sharing and fetal demise. METHODS: This was a prospective longitudinal cohort study of a consecutive series of monochorionic diamniotic twin pregnancies that underwent ultrasound assessments at 12, 16, 20 and 28 weeks' gestation. Fetal biometry (crown-rump length at 12 weeks or estimated fetal weight (EFW) thereafter) and cord insertion sites were recorded at each visit, as well as the diameter of the umbilical vein (UV) in both the intra-abdominal part and a free loop of the umbilical cord. Time-averaged maximum velocity in the intra-abdominal part of the UV was measured to calculate UV-flow. Univariate and multivariate linear regression analyses were performed to assess the relationship between intertwin ratios of these variables and placental sharing at 12, 16, 20 and 28 weeks' gestation. Placental sharing was calculated by dividing the larger by the smaller placental share, as measured on placental injection studies after birth. Additionally, the Mann-Whitney U-test and receiver-operating-characteristics-curve analysis were used to explore the relationship between the occurrence of fetal demise and intertwin differences in fetal biometry, cord insertion sites, UV diameters and flow at 12, 16, 20 and 28 weeks. RESULTS: Of 200 consecutive monochorionic twin pregnancies enrolled, injection studies were performed in 165 (82.5%) placentas. On univariate analysis, intertwin differences in fetal biometry, cord insertions and UV variables were associated significantly with placental sharing at 12, 16, 20 and 28 weeks' gestation. On multivariate analysis, intertwin differences in fetal biometry, cord insertions and all three UV variables remained associated significantly with placental sharing at 12 and 16 weeks. However, at 20 and 28 weeks, only the intertwin EFW ratio was associated consistently with placental sharing. Fetal demise of one or both twins complicated 26 (13.0%) pregnancies. Differences in EFW and cord insertion sites were not associated significantly with fetal demise, while at 16 weeks, differences in intra-abdominal UV diameter and flow were associated with an increased risk of subsequent fetal demise. CONCLUSIONS: At 12 and 16 weeks' gestation, intertwin differences in UV diameter and flow reflect placental sharing more accurately than do differences in fetal growth and cord insertion sites. At 16 weeks, discordance in intra-abdominal UV diameter and flow is also associated with an increased risk of fetal demise. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Outcome of Monochorionic Pregnancies after Selective Feticide with Bipolar Cord Coagulation: A German Single Center Experience.

OBJECTIVES: To review the outcome of complicated monochorionic pregnancies after fetoscopic selective feticide with bipolar cord coagulation in an experienced German center. METHODS: All cases that underwent selective feticide using fetoscopic bipolar umbilical cord occlusion (and simultaneous dissection in monoamniotics) at the University of Bonn in the past 10 years were retrospectively analyzed for antenatal and neonatal course and outcome. An adverse outcome was defined as either intrauterine death (IUD), neonatal death (NND), preterm prelabour rupture of membranes (PPROM), or preterm delivery (PTD) before 32.0 weeks of gestation. RESULTS: We diagnosed 56 monochorionic pregnancies, including 43 diamniotic and 8 monoamniotic twins, as well as 5 triplets, complicated by discordant fetal anomalies (n = 10), selective intrauterine growth restriction (n = 29), twin-to-twin transfusion syndrome (n = 13), twin reversed arterial perfusion sequence (n = 3), or severe early twin anemia polycythemia sequence (n = 1), that underwent fetoscopic selective feticide in the 10 years study period. Selective feticide was performed by bipolar cord coagulation at a median gestational age of 21.2 weeks. PPROM occurred in 11 cases, 7 (12.5%) before 32.0 weeks and 4 (7.1%) between 34.0 and 36.0 weeks, respectively. There were five (8.9%) co-twins IUDs at a median of 2 weeks after the intervention. We observed 12 (21.4%) PTDs before 32.0 weeks of gestation and 2 (3.6%) NNDs. Mean gestational age at delivery was 37.1 weeks, with an overall survival of the co-twin of 87.5%. CONCLUSION: In experienced hands, fetoscopic selective feticide is an effective treatment in complicated monochorionic pregnancies. By sacrificing a sick fetus that jeopardizes the entire pregnancy, a higher survival rate of the co-twin can be achieved.

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 outcomes and factors affecting the survival rate of fetuses with twin-to-twin transfusion syndrome treated with fetoscopic laser coagulation: a single-center seven-year experience.

OBJECTIVES: This single-center study aimed to assess the perinatal outcomes and its associated factors in fetuses with twin-to-twin transfusion syndrome (TTTS) treated by fetoscopic laser coagulation (FLC). METHODS: In this retrospective study, we included fetuses prenatally diagnosed with TTTS at Asan Medical Center, Seoul, Korea, between October 2011 and December 2018. All patients with TTTS stage II or higher and those with stage I TTTS coupled with symptomatic polyhydramnios or cardiac dysfunction were eligible for FLC. RESULTS: A total of 172 cases of monochorionic diamniotic twins and one case of dichorionic triamniotic triplets were prenatally diagnosed with TTTS and treated with FLC. The median gestational ages (GAs) at diagnosis and FLC were 20.3 and 20.5 weeks, respectively. The median GA of survivors at delivery was 32.5 weeks. The overall at least one twin- and double-survival rates within 28 days after birth were 82.1% and 55.5%, respectively. The GAs at diagnosis and FLC, Quintero stage, inter-twin weight discordance, associated selective intrauterine growth restriction (sIUGR), procedure time, volume of amnioreduction, preterm prelabor rupture of membranes (PPROM) within one week after FLC, intraoperative intrauterine bleeding, and chorioamnionitis were significant predictive factors of perinatal death. Associated sIUGR, absent end-diastolic flow of umbilical artery, and abnormal cord insertion were significantly associated with donor demise in utero, whereas lower GA at diagnosis and FLC, smaller twins at FLC, pulsatile umbilical vein, and presence of mitral regurgitation were significantly associated with recipient demise in utero. Since the application of the Solomon technique, the survival rate has improved from 75.4% to 88.8%. The FLC before 17 weeks was associated with PPROM within one week after FLC and lower survival rate, whereas that after 24 weeks was associated with twin anemia-polycythemia sequence and higher survival rate. We reached a survival rate of 82% for at least one survival with only 12 procedures. CONCLUSIONS: FLC is an effective treatment for TTTS. The learning curve reached the acceptable target faster than in previous studies. Several prenatal parameters are identified as predictive factors of fetal survival in TTTS treated with FLC.

Enhanced elimination of betamethasone in dichorionic twin pregnancies.

AIM: No study has evaluated the betamethasone pharmacokinetics in twin pregnancies according to chorionicity. This study aimed to describe and compare the betamethasone pharmacokinetic parameters in singleton and dichorionic (DC) and monochorionic twin pregnancies in the third trimester of pregnancy. METHODS: Twenty-six pregnant women received 2 intramuscular doses of 6 mg of betamethasone sodium phosphate plus 6 mg betamethasone acetate due to preterm labour. Serial blood samples were collected for 24 hours after the first intramuscular dose of betamethasone esters. Betamethasone plasma concentrations were quantified using a validated liquid chromatography-tandem mass spectrometry analytical method, and the pharmacokinetic parameters were obtained employing a noncompartmental model. Preliminary data on the betamethasone placental transfer are also presented. RESULTS: The geometric mean (95% confidence interval) of AUC0-∞ 645.1 (504.3-825.2) vs. 409.8 (311.2-539.6) ng.h/mL and CL/F 17.70 (13.84-22.65) vs. 27.87 (21.17-36.69) were significantly different, respectively, in singleton pregnancies when compared to DC twins. CONCLUSION: Data from this study suggest that the presence of 2 foetoplacental units may increase the betamethasone metabolism by hepatic CYP3A4 and/or placental 11ß-HSD2 enzymes. Pharmacokinetic-pharmacodynamic clinical studies are needed to investigate whether these betamethasone pharmacokinetic changes have clinical repercussions for the newborns and require dose adjustment in DC twin pregnancies.