Comment on “Single Fetal Demise in Twin Anemia–Polycythemia Sequence: Perinatal Outcome of Surviving Cotwin”

When blood flow between the two fetuses in a monochorionic twin pregnancy is imbalanced, serious complications can arise, including twin-twin transfusion syndrome (TTTS) and twin anemia-polycythemia (TAPS). TTTS involves relatively large placental anastomoses between the twins and can lead to amniotic fluid imbalance, whereas TAPS results from small intertwin placental anastomoses that cause chronic anemia in the donor twin and chronic polycythemia in the recipient. Prior studies show that single intrauterine fetal demise (IUFD) in monochorionic twin pregnancies with intertwin anastomoses can result in acute exsanguination of the surviving twin, potentially leading to brain injury or death. It is plausible that this effect may be attenuated in cases complicated by TAPS due to the small size and high resistance of the intertwin vessels, but this remains understudied. This study aims to better characterize the risk of adverse perinatal outcomes for the surviving fetus following IUFD in monochorionic twin pregnancies complicated by TAPS. This retrospective cohort study used data from twin pregnancies recorded in the international TAPS Registry between 2014 and 2023. Inclusion criteria were active TAPS and spontaneous single IUFD, while cases managed with selective reduction, termination of pregnancy, or preterm delivery were excluded. For each case, antenatal characteristics and obstetric, fetal, and neonatal outcomes were abstracted from medical records. The primary outcomes were mortality and severe neonatal cerebral injury in the surviving twin. A total of 432 twin pregnancies complicated by TAPS were identified, of which 39 involved a single IUFD. Most cases (n = 30, 77%) developed after laser surgery to treat TTTS, while the remainder (n = 9, 23%) occurred spontaneously. Management strategies included expectant management in 27 cases (69%), intrauterine transfusion in 10 cases (26%), and fetoscopic laser surgery in 2 cases (5%). Most IUFDs occurred in the donor twin (90%), and new-onset anemia was not observed in any surviving cotwins. Cotwin demise occurred in one case, attributed to suspected intrauterine fetal infection following premature rupture of membranes. No cases of neonatal cerebral injury were identified in surviving cotwins measured one day after delivery. Severe neonatal morbidity occurred in 8 cases (22%), most commonly due to respiratory distress syndrome. One case of perinatal asphyxiation occurred, but was attributed to pulmonary hypoplasia rather than fetal exsanguination. Previous studies have reported rates of severe cerebral injury of ∼25% following single IUFD in monochorionic twin pregnancies overall. In contrast, these findings suggest that the risks of mortality and brain injury in pregnancies complicated by TAPS are low. The authors suggest that these results could inform clinical decision-making when weighing the risks and benefits of rescue intrauterine transfusion versus expectant management. They caveat that the study is limited by a retrospective design, small sample size, short follow-up period, and the potential for underreporting in cases of double IUFD. (Summarized from van de Sande MJA, Lopriore E, Lanna M, et al. Single fetal demise in twin anemia-polycythemia sequence: Perinatal outcome of surviving cotwin. Ultrasound Obstet Gynecol. 2025;66(1):51–55. doi: https://doi.org/10.1002/uog.29242)