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Twin reversed arterial perfusion (TRAP) sequence is a rare complication of monochorionic twinning whereby a donor twin perfuses an acardiac twin via aberrant vascular anastomoses. The resulting paradoxical retrograde blood flow supplying the acardiac twin is oxygen-poor, leading to some of the most severe malformations encountered in humans. Though the first descriptions of acardiac twins date back to at least the 16th century, the pathophysiologic processes which underpin the development of TRAP sequence are still being elucidated. Theories on the pathogenesis of TRAP sequence include deficiencies intrinsic to the embryo and primary abnormalities of the placental vasculature. Autopsy studies continue to provide clues to the underlying pathogenesis of TRAP sequence, and the characterization of the spectrum of manifestations that can be observed in acardiac twins. Herein, we present the clinical, autopsy, and molecular findings in a unique case of TRAP sequence. Novel findings include a primitive cloaca-like structure and chromosomal aberrations involving 6q11.1 and 15q25.1.

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Pulmonary stenosis (PS) is a congenital heart diseases (CHDs) with a spectrum of stenosis. Monochorionic (MC) twins are at increased risk of CHDs, especially acquired CHDs in twin-twin transfusion syndrome (TTTS). PS/Pulmonary atresia (PA) is a rare coincidence with TTTS. MC twin pregnancies have increased in last decades due to increasing in maternal age and extensive use of assisted reproductive technologies. Therefore, attention to this group is important for heart abnormalities, especially in twins with TTTS. Multiple cardiac abnormalities in MC twins with TTTS are to be expected due to cardiac hemodynamic changes and may be eliminated by Fetoscopic laser photocoagulation treatment. Prenatal diagnosis of PS is necessary given the importance of treatment after birth.
We here present a case of coexistence of TTTS with PS in a growth restricted recipient twin who successfully treated with balloon pulmonary valvuloplasty in neonatal period. Also, we detected infundibular PS after valvuloplasty that treated with medical therapy (propranolol).
It is important to detect acquired cardiac abnormalities in MC twins with TTTS, and follow them up after birth to determine the need of intervention in neonatal period.

BACKGROUND: Twin anemia polycythemia sequence is a rare complication in monochorionic twin pregnancy.
METHODS: 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.

Twin-twin transfusion syndrome occurs in multiple gestations and involves a chronic flow of blood from one twin to another twin and is a rare entity. We present a case of 32-years-old primigravida with a twin pregnancy who presented with increasing abdominal girth inappropriate with her gestational age at 21 weeks of her pregnancy. Ultrasound findings were suggestive of twin-twin transfusion syndrome. The patient was provided with treatment options but due to polyhydramnios and short cervix, the patient went into spontaneous labour the same day with a poor pregnancy outcome. Twin-twin transfusion syndrome leads to a high rate of perinatal morbidity due to its poorly understood aetiology and difficulty in diagnosing and treatment. Early diagnosis during antenatal ultrasound is important in reducing morbidity and mortality rates.
UNASSIGNED: case reports; fetoscopy; oligohydramnios; polyhydramnios; twins.

In monochorionic twins with no evidence of chronic twin-to-twin transfusion syndrome or twin anemia-polycythemia sequence, a sudden onset of fetal transfusion syndrome after the second trimester of pregnancy is defined as acute twin-to-twin transfusion syndrome. Labor pain, change in the fetal position, and birth order are known risk factors for this condition, and the hemoglobin level of the donor twin is usually reported to be <12 g/dL. We report a recent case of acute twin-to-twin transfusion syndrome without effective labor pain causing cervical changes, resulting in fetal bradycardia and neonatal death after birth; however, the anemia of the donor twin was not as severe as has been reported previously in twin-to-twin transfusion syndrome cases.

OBJECTIVE: We aimed to investigate the prevalence and clinical outcomes of twin-to-twin transfusion syndrome (TTTS) with proximate cord insertions.
METHODS: This was retrospective cohort study of TTTS cases managed at single fetal center between 2012 and 2020. Presence of proximate cord insertions was defined as a distance of equal or less than 4 cm between placental cord insertions that was recorded based on sonographic and fetoscopic examinations. Clinical outcomes were investigated compared to unmatched cohort and to 1:2 matched controls using preoperative variables including Quintero staging, selective fetal growth restriction, anterior placenta, preoperative cervical length, and gestational age at fetal intervention. Systematic review and meta-analysis were conducted following PRSMA guidelines through searching PubMed, Scopus, CINAHL, and Medline databases from inception until January 2021.
RESULTS: The prevalence of proximate cord insertions in monochorionic placentas with TTTS was 2% (5/246). All 5 cases were managed by fetoscopic laser surgery (FLS). Procedure time was significantly longer (mean: 61.4 min in proximate cord vs. 37.5 min in nonproximate cord, p < 0.001), and amnioinfusion was significantly more common (100% in proximate cord vs. 43% in nonproximate cord, p = 0.01). Perinatal survival and neonatal outcomes were not different between groups. Similar findings were seen following 1:2 control matching. Systematic review yielded total of 19 case reports of which different management options were applied including FLS (n = 13), amniodrainage (n = 3), and selective reduction (n = 3). Clinical outcomes results were mixed and inconsistent. FLS was described as technically challenging and residual anastomosis was common. Overall fetal and neonatal survival following FLS was 85% and 80%, respectively.
CONCLUSIONS: Presence of proximate cords in TTTS cases poses serious technical challenges even for highly experienced surgeons. Feasibility should be only determined by fetoscopic examination.

BACKGROUND: In utero limb ischemia is a rare complication of the monochorionic twin pregnancies complicated with twin to twin transfusion syndrome (TTTS). The condition is more often seen in recipient twins. There are few theories of the pathogenesis including in utero venous thromboembolism, but the cause remains unclear. However, limb ischemia is thought to be unrelated with any prenatal intervention.
METHODS: We present a case of a monochorionic twin pregnancy complicated with TTTS admitted to the Clinic for selective fetoscopic laser photocoagulation. The invasive procedure failed due to poor visibility. In the following weeks of pregnancy, amnioreduction procedures were performed. At 28 weeks of gestation due to twin anemia-polycythemia sequence diagnosis the patient was qualified for cesarean section. Postnatally, the donor twin was diagnosed with lower right limb ischemic necrosis. The extremity was amputated 2 days later with an uncomplicated recovery. After speculations of the potential pathogeneses it was suggested that the ischemic limb occurred as a complication of the main condition - TTTS.
CONCLUSIONS: In literature, there have been no cases reported of TTTS stage I complicated with donor twin limb ischemia. The actual cause of the in utero limb ischemic necrosis in monochorionic twins remains unknown. Nevertheless, increased attention to the potential complication after failed invasive procedures or conservative treatment should be required.

Clinically significant extrauterine twin-twin transfusion syndrome in conjoined twins is rare and carries a high risk of perinatal mortality. The ensuing postnatal imbalance in circulation across connecting vessels results in hypovolemia in the donor and hypervolemia in the recipient. Data on management and treatment are sparse especially in the setting of a single ventricle congenital heart defect. We present a case of a pair of omphalopagus conjoined twins, one with a single ventricle physiology (Twin B), who developed twin-twin transfusion syndrome shortly after birth. The resulting pathophysiology in the setting of a single ventricle congenital heart defect created added layers of complexity to their management and expedited surgical separation. Shunting from Twin B to Twin A-with an anatomically normal heart-resulted in mal-perfusion and rapid deterioration jeopardizing the health of both twins. In the preoperative course, steps taken to medically optimize the twins prior to surgery and the anesthetic considerations are detailed in this report.