Magnetic resonance imaging of intracranial anomalies in pregnancies complicated by twin anemia-polycythemia sequence.

PURPOSE: To describe fetal brain Magnetic Resonance Imaging (MRI) findings in a large series of monochorionic (MC) pregnancies complicated by Twin Anemia-Polycythemia Sequence (TAPS) prenatally diagnosed, so to characterize the potential intracranial complications associated with this condition, their frequency and potential treatment options. METHODS: This is a retrospective study of MC twin pregnancies complicated by TAPS and undergone fetal MRI in a single institution from 2006 to 2023. MRI control was performed and post-natal ultrasound (US) or MRI were available. RESULTS: 1250 MC pregnancies were evaluated in our institution. 50 pregnancies (4%) were diagnosed with TAPS, 29 underwent a fetal brain MRI. 13/29 pregnancies (44.8%) demonstrated brain findings at MRI in at least a twin. Neuroradiological findings were detected in 14/57 twins (24.6%). We detected four main categories of findings: hemorrhagic lesions, T2-weighted white-matter hyperintensities (WMH), brain edema-swelling and venous congestion. Nineteen findings were present in the anemic and three in the polycythemic twins, with a statistically significant ratio between the two groups (p-value = 0.01). Intrauterine MRI follow-up demonstrated the sequalae of hemorrhagic lesions. A complete regression of brain swelling, veins prominence and T2-WMHs was demonstrated after treatment. Postnatal imaging confirmed prenatal features. CONCLUSIONS: Our work demonstrates that TAPS-related MRI anomalies consisted in edematous/hemorrhagic lesions that occur mostly in anemic rather than in polycythemic twins. Fetoscopic laser surgery could have a potential decongestant role. Therefore, prenatal MRI may help in counselling and management in TAPS pregnancies, especially for the planning of therapy and the monitoring of its efficacy.

Suspected twin anemia polycythemia sequence in a dichorionic, diamniotic twin pregnancy: a case report.

BACKGROUND: Twin anemia polycythemia sequence is a rare complication in monochorionic twin pregnancy. CASE PRESENTATION: We describe a case of dichorionic twin pregnancy presenting with suspected twin anemia polycythemia sequence. A 31-year-old White female, on her third pregnancy, had a routine ultrasound scan at 12 weeks gestation, which demonstrated a dichorionic twin pregnancy with one placenta located in the anterior wall and the other in the posterior wall of the uterus. At 21 weeks, a scan demonstrated a 24% growth discordance between the two fetuses with normal Doppler studies and amniotic fluid. At 27 weeks, one twin showed signs of anemia and the other polycythemia; the fetal middle cerebral artery peak systolic velocity was high in the anemic fetus and low in the polycythemic twin (1.8 and 0.5 multiples of the median). An intrauterine blood transfusion was carried out and this increased the fetal hemoglobin concentration in the anemic twin from 3.5 to 12.5 g/dL. At 29 weeks, delivery by cesarean section was carried out because of evidence from middle cerebral artery peak systolic velocity of recurrence of anemia in one twin and worsening polycythemia in the co-twin; at birth the hemoglobin concentrations were 5.6 and 24.9 g/dL, respectively. Histopathological examination confirmed dichorionicity with no communicating vessels between the two placentas. CONCLUSIONS: This is the first case of twin anemia polycythemia sequence in a dichorionic, diamniotic twin pregnancy where intrauterine blood transfusion was used to prolong the pregnancy by almost 2 weeks in a "twin anemia polycythemia sequence-like" setting.

A Rare Dichorionic Triamniotic Triplet Pregnancy with Spontaneous Twin Anemia-Polycythemia Sequence between Two Dichorionic Fetuses.

INTRODUCTION: This report presents a rare case of spontaneous twin anemia-polycythemia sequence (TAPS) between two dichorionic fetuses in a spontaneous, homozygotic, dichorionic, triamniotic, triplet pregnancy treated with multiple intrauterine blood transfusions (IUTs) and partial exchange transfusions (PETs). CASE PRESENTATION: The pregnancy was diagnosed with stage IV TAPS at gestational week 25+1. The patient was treated with laser surgery combined with multiple IUTs and PETs. The triplets were delivered at a planned caesarean section at gestational week 28+1 with postnatal hemoglobin values of 18.21, 26.43, and 11.92 g/dL in triplet 1, 2, and 3, respectively. At 4 years of age, triplet 1 is considered healthy, triplet 2 is diagnosed with mild mental retardation, and triplet 3 with profound mental retardation and dystonic cerebral palsy. DISCUSSION: This is an extremely rare case of TAPS between dichorionic fetuses in a triplet pregnancy, and routine surveillance with measurement of middle cerebral artery peak systolic velocity in dichorionic pregnancies may contribute to the detection of similar cases in the future. Furthermore, this case contributes with rare long-term follow-up data of children treated for high-stage TAPS with multiple IUTs and PETs.

Fetal and neonatal brain injury in twins complicated by twin anemia polycythemia sequence.

OBJECTIVES: To determine the rate of fetal and neonatal brain lesions and define risk factors for such lesions in pregnancies complicated by Twin Anemia Polycythemia Sequence (TAPS). METHODS: A retrospective cohort study of monochorionic twin pregnancies which were diagnosed with TAPS in a single tertiary medical center between 2013 and 2021. Pregnancies were followed with fetal brain neurosonogram every 2 weeks and fetal brain MRI (magnetic resonance imaging) was performed when indicated at 28-32 weeks of gestation; post-natal brain imaging included neonatal brain ultrasound. Pregnancies with pre- and post-natal brain lesions were compared to those without such findings. RESULTS: Overall, 23 monochorionic diamniotic pregnancies were diagnosed with TAPS over the study period resulting in perinatal survival of 91.3% (42/46). In 6/23 (26%) pregnancies and 7/46 (15.2%) fetuses pre- or post-natal brain lesions were detected, of whom five were the polycythemic twins and two were the anemic twins. Brain findings included intra-cerebral hemorrhage and ischemic lesions and were diagnosed prenatally in 6/7 (85.7%) cases. No risk factors for severe brain lesions were identified. CONCLUSIONS: TAPS may place the fetuses and neonates at increased risk for cerebral injuries. Incorporation of fetal brain imaging protocols may enhance precise prenatal diagnosis and allow for accurate parental counseling and post-natal care.

Clinical and Radiological Profile of Cerebrovascular Disease in Polycythemia: Analysis of Neurologic Manifestations from a Tertiary Center in South India.

PURPOSE: Patients with polycythemia, either primary or secondary, are at elevated risk for thrombotic complications, including stroke. We aimed to investigate the clinical and radiological characteristics of cerebrovascular disease (CVD) in polycythemia, and describe other neurologic manifestations. METHODOLOGY: We conducted a cross-sectional study of patients diagnosed with polycythemia between 2014 and 2019 at a tertiary care center and collected relevant medical data with a special focus on cerebrovascular disease and neurologic manifestations. We performed descriptive and inferential analyses. We have also described and analyzed the available neuroimaging features. RESULTS: We analyzed data from 56 patients. 20 patients (35.7%) had ischemic stroke. The incidence of CVD was higher in those with primary polycythemia (43%) than in those with secondary polycythemia (8%). The most common subtype of stroke was large vessel disease, and the most common arterial territory was the anterior circulation. There was no statistically significant difference in the hematocrit level between those with or without CVD. Neuroimaging revealed multiple large vessel intracranial stenoses on MR Angiography, and hyperdense vessels on plain CT. Other neurologic manifestations included headache, seizures, dizziness, visual symptoms and papilledema, and these were significantly more common in primary polycythemia. CONCLUSIONS: CVD is common in patients with polycythemia. The most common type observed was large vessel occlusion, predominantly in the anterior circulation. In stroke patients, multiple vessel stenosis and hyperdense vessels may be clues to polycythemia.

Twin anemia polycythemia sequence: Successful laser photocoagulation treatment and placental histopathological findings.

OBJECTIVE: Twin anemia polycythemia sequence (TAPS) is a rare complication of monochorionic twin pregnancies, which can occur either spontaneously or after laser photocoagulation procedure for twin to twin transfusion syndrome. TAPS is associated with poor perinatal outcomes and clear screening guidelines for this disease are lacking resulting in under-diagnosis of TAPS. CASE REPORT: The purpose of this report is to discuss a case of severe spontaneous TAPS, which was successfully treated with favorable outcome, to describe the placental histopathological findings, and to propose an algorithm for management and follow up of this rare condition. CONCLUSION: Laser photocoagulation of the placental anastomoses, despite technical challenges, can be safely performed in cases of TAPS. Even with prenatal evidence of successful resolution of TAPS, close fetal surveillance is warranted because of the persistence of placental villous immaturity.

Twin Anemia Polycythemia Sequence in a Dichorionic Twin Pregnancy Leading to Severe Cerebral Injury in the Recipient.

Twin anemia polycythemia sequence (TAPS) is a form of chronic imbalanced feto-fetal transfusion through minuscule placental anastomoses leading to anemia in the TAPS donor and polycythemia in the TAPS recipient and has been reported only in monochorionic twins. We report a very unusual case of TAPS which developed in a dichorionic twin pair, born at a gestational age of 33+2. Twin 1 (recipient) was polycythemic and had a hemoglobin value of 22.4 g/dL, whereas twin 2 (donor) was anemic with a hemoglobin value of 9.8 g/dL and an increased reticulocyte count (72‰). Color dye injection of the placenta revealed the presence of a deep-hidden small veno-venous anastomosis. Dichorionicity was confirmed on histologic examination. Aside from respiratory distress syndrome, the donor twin had an uncomplicated neonatal course. The recipient twin developed a post-hemorrhagic ventricular dilatation requiring treatment with a ventriculoperitoneal shunt and Rickham reservoir. This report shows that in dichorionic twins, placental anastomoses can be present, which can lead to the development of TAPS with severe consequences. Therefore, when a pale and plethoric dichorionic twin pair is born, a complete diagnostic work-up is required, including a full blood count with reticulocytes and placental injection, to investigate the presence and nature of potential underlying feto-fetal transfusion. Once the diagnosis of TAPS has been established, cerebral ultrasound, hearing screening, and long-term follow-up are strongly recommended as these twins have increased risk for severe cerebral injury, hearing loss, and long-term neurodevelopmental impairment.

More Than a Myoma: A Review of Myomatous Erythrocytosis Syndrome.

Myomatous erythrocytosis syndrome (MES) is gynaecological condition marked by isolated erythrocytosis and a fibroid uterus. This report presents a case of MES and reviews common clinical presentations, hematological trends, and patient outcomes. This study was a combined case report and review of published cases of MES. Cases were identified using Medline and EMBASE databases. Binomial statistics were used to compare clinical characteristics among patients with MES. Kruskal-Wallis one-way analysis of variance was used to compare hematological values across time points (Canadian Task Force Classification III). A total of 57 cases of MES were reviewed. The mean age at presentation was 48.7 years. Commonly reported signs or symptoms at presentation include abdominopelvic distension or mass (93%), skin discolouration (33%), and menstrual irregularities (25%). There was no difference in parity (P = 0.42), menopausal status (P = 0.87), or hydronephrosis on imaging (P = 0.48) among patients. Preoperative phlebotomy to reduce the risk of thromboembolic complications was performed in half of all cases. On average, a 51% reduction in serum erythropoietin levels was observed following surgical resection (P = 0.004). In conclusion, patients with MES present with signs and symptoms attributed to either an abdominopelvic mass or erythrocytosis. Preoperative phlebotomy to decrease the severity of erythrocytosis has been used to mitigate the risk of thrombotic complications. Surgical resection of the offending leiomyoma is a valid approach for the treatment of MES.

Erythrocytosis is associated with intradialytic hypotension: a case series.

BACKGROUND: For patients with end stage renal disease undergoing hemodialysis, erythrocytosis occurs rarely. Erythrocytosis increases the risk of thrombosis, which is a common complication in hemodialysis patients. The risk of thrombosis may also be increased by hypotension. The purpose of our report is to examine the relationship between intradialytic hypotension and erythrocytosis. CASE PRESENTATION: We present a series of five patients with end stage renal disease and erythrocytosis (peak hemoglobin range 15.2-18.5 g/dL). All were erythropoiesis-stimulating agent naïve and non-smokers. Prior to developing erythrocytosis, each patient developed recurring episodes of intradialytic hypotension over several months. A statistically significant inverse correlation was observed between nadir intradialytic systolic blood pressure and hemoglobin concentration. In the index case, midodrine treatment resulted in resolution of the hypotension and erythrocytosis. Most of the patients had multiple acquired renal cysts, which is a potential source of erythropoietin. Four of the five cases developed arteriovenous dialysis access or deep venous thrombosis. CONCLUSIONS: An association between intradialytic hypotension and erythrocytosis was observed in five cases. We postulate that chronic intermittent hypotension and renal ischemia may lead to erythropoietin secretion, and this cascade could represent a newly recognized cause of secondary erythrocytosis.

Gerstmann syndrome complicating polycythemia secondary to anabolic steroid use.

Anabolic steroid use is prevalent among athletes and bodybuilders. There are known cardiovascular, reproductive, musculoskeletal and neuropsychiatric risks associated with their prolonged use. Although there have been very few documented cases of strokes associated with anabolic steroid use, cardiomyopathy and secondary erythropoiesis can increase the risk of strokes in users with no other risk factors. We present a 49-year-old man with left parietal ischaemic stroke with haemorrhagic conversion resulting in Gerstmann syndrome secondary to a hypercoagulable state from chronic anabolic steroid use.

The role of 18F-FDG PET in the assessment of a benign hematological disorder: polycythemia.

Fluorine-18 fluorodeoxyglucose positron emission tomography (18F-FDG PET) imaging was conceived in the early 1970 by investigators at the University of Pennsylvania as a research technique to measure brain metabolism and function by employing a non-invasive imaging approach. Soon after the introduction of whole-body PET instruments, 18F-FDG was utilized in the assessment of a variety of solid tumors and certain hematological malignancies. Yet, the role of 18F-FDG in assessing benign and uncommon malignant disorders of the bone marrow has not been investigated to a great extent. Fluorine-18-FDG as a molecular probe has the proven capacity to reflect the abnormal glycolytic activities inherent to a variety of disorders, where such information may serve as a guide to the clinical course of the respective disease. Recent efforts have studied bone marrow and extra-medullary disease activity in certain malignancies like chronic lymphocytic leukemia. Nonetheless, few studies have explored the role of 18F-FDG in assessing the metabolic basis of benign disorders of red marrow. Moreover, the introduction of novel imaging analysis schemes in recent years has allowed for the global assessment of red marrow disease, which can provide a superior means for characterizing the systemic nature and burden of these disorders. Accordingly, semi-quantitative global analysis techniques as applied to the skeletal structures in 18F-FDG PET may provide a tool to better understand these complex marrow abnormalities. Functional imaging of red bone marrow may also reveal critical information specifically regarding the extra-medullary extension of such hematological disorders that cannot be assessed by other diagnostic or imaging techniques. Myleoproliferative neoplasms (MPN) are an apt category of hematological disease that confer significantly altered systemic metabolic rates of hematopoietic stem cells (HSC) in the marrow, as such they are primed for exploration with 18F-FDG PET. The hallmark of such disorders involves the excess production of particular cellular components in blood. After a period of excess production, scar tissue may develop in place of the HSC leading to myleofibrosis and decreased hematopoietic activity. One of the least studied disorders within the larger category of MPN with respect to the nuclear medicine is polycythemia. Polycythemia may be either primary, polycythemia vera (PV), or secondary. PV involves a JAK2+ in HSC which allows for the excessive proliferation of immature erythrocytes and depressed erythropoietin levels as a result. Secondary polycythemia occurs in response to decreased oxygen intake, often as a result of smoking, which results in increased erythropoietin and hematocrit levels. Primary and secondary polycythemia lead to an increase in overall red marrow activity and a diffusion of active red marrow into the appendicular skeleton. Clinical presentation often includes redness or irritation of the skin along with headache, fatigue and excessive bleeding. Based upon the mentioned precedent, it is evident that PET imaging with 18F-FDG and other tracers will play a meaningful role in assessing diffuse bone marrow disorders such as hematological malignancies and myeloproliferative abnormalities. Semi-quantification studies of global bone marrow activity in such an application will be a vital means in accurately assessing the systematic nature and global burden of such benign hematological disorders such a polycythemia. Accordingly, the derived metabolic data projects to be a useful tool in the prospective clinical and scientific aspects of the diagnosis of these benign hematological disorders and the assessment of disease progression in light of relevant biological treatments. Given the nature of the disease and the enumerated capabilities of 18F-FDG PET it is expected that one would be able to capture the systematic abnormalities inherent to the disease. Moreover, the handful of case studies supports this possibility. Three case studies have all illustrated diffuse elevated 18F-FDG uptake throughout the axial and appendicular skeleton that reflects the hyper-metabolic red bone marrow as related to polycythemia. Moreover, the use of various functional imaging tracers, in addition to 18F-FDG, may indirectly reflect hypermetabolism in red bone marrow through abnormal tracer accumulation in the skeletons of patients. The whole body 18F-FDG scan of a JAK2+ PV patient before treatment (a) as compared to a matched subject (b) is found below; of note is the PV patient's elevated uptake in the pelvis, femur and spine.

Twin anemia-polycythemia sequence and routine monitoring practices amongst maternal-fetal medicine specialists in the United States: an initial investigation.

Background The purpose of this initial investigation was to begin to understand the routine twin anemia-polycythemia sequence (TAPS) monitoring practices of maternal-fetal medicine specialists (MFM specialists) in the United States in the absence of a formal guideline. Methods This study used an anonymous, online survey of 90 MFM specialists who were practicing in the United States. A $5 gift card to an online store was used to incentivize participants. Descriptive statistics were calculated. Results All MFM specialists reported at least some familiarity (100.00%) with TAPS. Most participants (92.94%) were familiar with methods for monitoring patients for TAPS and nearly all (97.50%) responded that they use 'Doppler MCA-PSV' to make a prenatal TAPS diagnosis. Nearly two-thirds of MFM specialists surveyed (65.06%) reported performing regular TAPS monitoring for patients with monochorionic-diamniotic (MCDA) pregnancies. Conclusion Despite no formal guidelines, the majority of American MFM specialists surveyed are using routine TAPS screening in their management of MCDA twin pregnancies, suggesting that the MFM specialists included in this study consider it a valuable diagnostic tool. Future research should further explore this possible trend toward routine TAPS monitoring amongst MFM specialists in the United States, as well as the potential value of routine TAPS monitoring in MCDA pregnancy.

Nonmosaic somatic HIF2A mutations associated with late onset polycythemia-paraganglioma syndrome: Newly recognized subclass of polycythemia-paraganglioma syndrome.

BACKGROUND: Somatic mutations in hypoxia-inducible factor 2α (HIF2A) are associated with polycythemia-paraganglioma syndrome. Specifically, the classic presentation of female patients with recurrent paragangliomas (PGLs), polycythemia (at birth or in early childhood), and duodenal somatostatinomas has been described. Studies have demonstrated that somatic HIF2A mutations occur as postzygotic events and some to be associated with somatic mosaicism affecting hematopoietic and other tissue precursors. This phenomenon could explain the development of early onset of polycythemia in the absence of erythropoietin-secreting tumors. METHODS: Correlation analysis was performed between mosaicism of HIF2A mutant patients and clinical presentations. RESULTS: Somatic HIF2A mutations (p.A530V, p.P531S, and p.D539N) were identified in DNA extracted from PGLs of 3 patients. No somatic mosaicism was detected through deep sequencing of blood genomic DNA. Compared with classic syndrome, both polycythemia and PGL in all 3 patients developed at an advanced age with polycythemia at age 30, 30, and 17 years and PGLs at age 34, 30, and 55 years, respectively. Somatostatinomas were not detected, and 2 patients had ophthalmic findings. The biochemical phenotype in all 3 patients was noradrenergic with 18 F-fluorodopa PET/CT as the most sensitive imaging modality. All patients demonstrated multiplicity, and none developed metastatic disease. CONCLUSION: These findings suggest that newer techniques need to be developed to detect somatic mosaicism in patients with this syndrome. Absence of HIF2A mosaicism in patients with somatic HIF2A mutations supports association with late onset of the disease, milder clinical phenotype, and an improved prognosis compared with patients who have HIF2A mosaicism.

In utero Partial Exchange Transfusion Combined with in utero Blood Transfusion for Prenatal Management of Twin Anemia-Polycythemia Sequence.

Monochorionic twin pregnancies are at risk of unique complications due to placental sharing and vascular connections between placental territories assigned for each twin. Twin anemia-polycythemia sequence (TAPS) is an infrequent but potentially dangerous complication of abnormal placental vascular connections. TAPS occurs due to very-small-caliber (< 1 mm) abnormal placental vascular connections which lead to chronic anemia in the donor twin and polycythemia in the recipient twin. TAPS may occur spontaneously or following fetoscopic laser photocoagulation of communicating placental vessels for twin-twin transfusion syndrome. One of the hallmarks of TAPS is the absence of polyhydramnios and oligohydramnios. The postnatal diagnosis is based on significant hemoglobin discrepancy between the twins. Middle cerebral artery peak systolic velocity Doppler ultrasound allows for the prenatal diagnosis of TAPS. The optimal prenatal treatment and intervention timing has not been established. Here, we report 3 spontaneous TAPS cases diagnosed and managed in the prenatal period with a combination of in utero blood transfusion for the anemic twin (donor) and in utero partial exchange transfusion for the polycythemic twin (recipient). These cases contribute to the limited outcome data of this underutilized method for the management of TAPS.

Improved prediction of twin anemia-polycythemia sequence by delta middle cerebral artery peak systolic velocity: new antenatal classification system.

OBJECTIVES: To investigate the diagnostic accuracy of delta middle cerebral artery peak systolic velocity (MCA-PSV) > 0.5 multiples of the median (MoM) and compare its predictive value with that of the current MCA-PSV cut-off values of > 1.5 MoM in the donor and < 1.0 MoM in the recipient, for the diagnosis of twin anemia-polycythemia sequence (TAPS) in monochorionic twin pregnancy. METHODS: This was a retrospective consecutive cohort study comprising all uncomplicated monochorionic twin pregnancies and twin pregnancies with a postnatal diagnosis of TAPS managed between 2003 and 2017 in the Dutch national referral center for fetal therapy. Cases with incomplete MCA-PSV Doppler measurements 1 week prior to delivery or with incomplete hemoglobin measurements within 1 day after birth were excluded. The postnatal diagnosis of TAPS was based on an intertwin hemoglobin difference > 8 g/dL and at least one of the following: reticulocyte count ratio > 1.7 or presence of minuscule anastomoses on the placental surface. We compared the predictive accuracy of the current diagnostic method using MCA-PSV cut-off values of > 1.5 MoM in the donor and < 1.0 MoM in the recipient with that of a new method based on intertwin difference in MCA-PSV > 0.5 MoM for prediction of TAPS. RESULTS: In total, 45 uncomplicated and 35 TAPS monochorionic twin pregnancies were analyzed. The sensitivity and specificity of the cut-off MCA-PSV values (donor > 1.5 MoM, recipient < 1.0 MoM) to predict TAPS was 46% (95% CI, 30-62%) and 100% (95% CI, 92-100%), respectively; positive predictive value was 100% (95% CI, 81-100%) and negative predictive value 70% (95% CI, 58-80%). Delta MCA-PSV showed a sensitivity of 83% (95% CI, 67-92%) and a specificity of 100% (95% CI, 92-100%); the positive and negative predictive values were 100% (95% CI, 88-100%) and 88% (95% CI, 77-94%), respectively. Of the 35 cases with TAPS diagnosed postnatally, 13 twin pairs showed a delta MCA-PSV > 0.5 MoM but did not fulfill the cut-off MCA-PSV criteria. Of these 13 TAPS twins, nine donors and four recipients had normal MCA-PSV values. There was a high correlation between delta MCA-PSV and intertwin difference in hemoglobin level (R = 0.725, P < 0.01). CONCLUSION: Delta MCA-PSV > 0.5 MoM has a greater diagnostic accuracy for predicting TAPS compared to the current MCA-PSV cut-off criteria. We therefore propose a new antenatal classification system for TAPS. In monochorionic twin pregnancies with delta MCA-PSV > 0.5 MoM on Doppler ultrasound, but normal MCA-PSV values in the donor or recipient, obstetricians should be aware of the therapeutic implications and neonatal morbidities associated with TAPS. © 2018 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of the International Society of Ultrasound in Obstetrics and Gynecology.

Role of fetal intertwin difference in middle cerebral artery peak systolic velocity in predicting neonatal twin anemia-polycythemia sequence.

OBJECTIVES: To evaluate the relationship between the fetal intertwin difference in middle cerebral artery peak systolic velocity (MCA-PSV) and intertwin difference in hemoglobin (Hb) concentration at birth in monochorionic diamniotic (MCDA) twin pregnancies in order to assess its potential role in the prediction of twin anemia-polycythemia sequence (TAPS). METHODS: This was a retrospective cohort study of MCDA twin pregnancies delivered between January 2012 and January 2018. All pregnancies with measurements of MCA-PSV within 7 days prior to delivery and in which neonatal Hb concentration was available were included. The correlation between fetal intertwin difference in MCA-PSV, expressed in multiples of the median (MoM), and neonatal intertwin difference in Hb concentration was investigated. Receiver-operating characteristics (ROC) curve analysis was used to assess the performance of fetal intertwin difference in MCA-PSV for predicting intertwin difference in Hb > 90th centile at birth. RESULTS: A total of 154 out of 256 MC twin pregnancies fulfilled the inclusion criteria. Fetal intertwin difference in MCA-PSV MoM correlated positively with neonatal intertwin difference in Hb concentration (r = 0.79; P < 0.001). The 90th centile for intertwin difference in Hb was 7.25 g/dL. There were 15 (9.7%) cases with a Hb difference ≥ 7.25 g/dL at birth. ROC curve analysis showed a high accuracy of fetal intertwin MCA-PSV MoM difference for the prediction of neonatal intertwin Hb difference ≥ 7.25 g/dL at birth (area under the ROC curve, 0.976 (95% CI, 0.935-0.993); P = 0.012). The optimal cut-off for intertwin MCA-PSV MoM difference was 0.373, with a sensitivity of 93.3% (95% CI, 68.1-99.8%) and a specificity of 95.7% (95% CI, 90.8-98.4%). The positive predictive value was 70% (95% CI, 45.7-88.1%) and the negative predictive value was 99.3% (95% CI, 95.9-100%). CONCLUSION: Our findings show that fetal intertwin MCA-PSV MoM difference is a good predictor of neonatal intertwin Hb concentration difference > 90th centile and potentially of TAPS. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.