Twin anemia polycythemia sequence in discordant dichorionic twins.

A 23-year-old primiparous woman with spontaneous dichorionic pregnancy was diagnosed by early ultrasonography. She developed hypertensive disorder of pregnancy at 27 weeks of gestation. At 29 weeks and 3 days of gestation, she was transferred to our perinatal center due to increasing discrepancy between the fetal weights (fetus A 1203 g, fetus B 989 g). Notably, polyhydramnios-oligohydramnios sequence was not observed. An emergency cesarean section was performed at 31 weeks 1 day of gestation because of elevated liver enzyme levels. Two male neonates were delivered with birth weights of 1413 and 1098 g, respectively. At birth, twin A was peripherally cyanotic with hemoglobin of 26.4 g/dL and a reticulocyte count of 4.1%. He was treated using partial exchange transfusion for polycythemia. Twin B was pale with hemoglobin of 7.8 g/dL and a reticulocyte count of 20.5%; thus, an emergent red blood cell transfusion was performed for anemia. Based on their hematological values, the twins were diagnosed with twin anemia polycythemia sequence (TAPS). A marked difference in the coloration of the maternal surface was observed in the two placentas on a macroscopic examination (Fig. 1); however, no vascular anastomosis was detected during dye studies. Microscopic histopathology revealed two amniotic layers and two chorionic layers, which confirmed dichorionicity. Recent literature reviews reported that twin-to-twin transfusion syndrome (TTTS) or TAPS occurs in dichorionic twin placentas with evidence of vascular anastomoses, although it is extremely rare.1Kanagaretnam D. Nayyar R. Zen M. Twin anemia polycythemia sequence in dichorionic diamniotic twins: a case report and review of the literature.Clin Case Rep. 2021; 9e04184Crossref Scopus (1) Google Scholar, 2Lanna M. Faiola S. Casati D. Rustico M.A. Twin-twin transfusion syndrome in dichorionic twin pregnancy: rare but not impossible.Ultrasound Obstet Gynecol. 2019; 54: 412-418Crossref Scopus (2) Google Scholar, 3Zilliox M. Koch A. Farve R. Sananes N. Unusual twin anemia-polycythemia sequence in a dichorionic diamniotic pregnancy.J Gynecol Obstet Hum Reprod. 2019; 48: 359-361Crossref Scopus (4) Google Scholar Miniscule anastomoses undetectable by a dye study may have been present in our dichorionic twins. Prenatal diagnosis, close monitoring, appropriate early delivery, and postnatal management are necessary to improve the outcomes of TTTS and TAPS. Thus, this report highlights the importance of prenatal recognition and postnatal confirmation of TTTS or TAPS, regardless of chorionicity. S.H. and S.I. drafted the initial manuscript. S.H., S.I. and S.T. treated the patient, and contributed to the acquisition of clinical data and imaging. M.Y. performed pathological evaluation. S. Y. supervised the manuscript. All authors approved the final manuscript. The authors have no conflicts of interest to declare. We thank the patient's parents for their kind cooperation. We also thank Dr. Chizen Tarui, Department of Neonatology, and Dr. Tomoko Kibara and Megumi Kaneko, Department of Obstetrics, in Hyogo Prefectural Kobe Children's Hospital for their support.