Supplementary Material for: Diagnosis and Management of Spontaneous Twin Anemia-Polycythemia Sequence during Early Second-Trimester: A Case Report

Introduction Spontaneous twin anemia-polycythemia sequence complicates about 3-5% of monochorionic pregnancies. This complication is associated with severe neurological morbidity and mortality in some cases. Prenatal diagnosis relies on Doppler assessment of the middle cerebral artery peak systolic velocity. However, there is ongoing debate regarding the appropriate gestational age to initiate surveillance. Case report We present a case of stage III twin anemia-polycythemia sequence, first identified at 16 weeks of gestation, given discordant middle cerebral artery peak systolic velocity (1.8 and 0.7 MoM in the anemic and polycythemic twin, respectively. Delta MCA PSV MoM 1.1), starry sky liver appearance, discordance in echogenicity and thickness of placental territories and intermittently absent end-diastolic flow in the umbilical artery of the polycythemic twin, successfully managed with fetoscopic laser photocoagulation at 17 weeks of gestation. A cesarean delivery was performed at 31 weeks of gestation by the referring team due to concomitant fetal growth restriction with lack of interval growth, abnormal umbilical artery Dopplers, and non-reassuring fetal status. Pathology confirmed ablation of all anastomotic vessels. The hemoglobin count was within normal limits for both babies (15.9 and 14.9 g/dL), and they were deemed stable for discharge at corrected gestational ages of 37 and 38 weeks, respectively. Conclusion Middle cerebral artery peak systolic velocity Doppler surveillance starting at 16 weeks of gestation is important for early detection and timely intervention of monochorionic pregnancies complicated by early severe spontaneous twin anemia-polycythemia sequence.