Placental vascular recruitment after single intrauterine demise: A newly diagnosed phenomenon unique to monochorionic pregnancies

Abstract

Monochorionic (MC) twin pregnancies are at high risk of fetal demise, which occurs in about 11% of diamniotic and 18% of monoamniotic twin pregnancies. 1,2 This excessive mortality is largely caused by the shared circulation, which can lead to acute or chronic intertwin transfusion imbalances. Such imbalances probably also account for the high incidence of congenital anomalies, occurring in up to 6% of diamniotic 1 and 23% of monoamniotic 2 pairs and usually affecting only one twin. In places where termination is legally permitted, coagulation of the umbilical cord can be offered to selectively reduce the anomalous twin. 3 If one of a twin pair dies during pregnancy, either spontaneously or after selective reduction, its placental part is no longer perfused and degenerates. 4In our hospital, we routinely inject all MC twin placentas that resulted in two livebirths with contrast dye for research purposes.We usually do not inject placentas with intrauterine demise remote from birth, as due to maceration the angio-architecture can no longer be examined. We report on three placentas with intrauterine demise of one twin, one spontaneous demise in a monoamniotic pair and two after cord coagulation in a diamniotic setting, where the placental share of the demised twin did not degenerate but was entirely recruited by the surviving co-twin.Our technique for placental injection has been described elsewhere. 5 In these cases, we injected the cord vessels of the surviving twin with coloured barium sulphate (Micropaque, Guerbet group, Paris, France). We took a digital photograph of the placental surface as well as an X-ray angiogram. The initial vascular equator was estimated and delineated on the photograph and the share of each twin was measured using ImageJ software (https://imagej.nih.gov/ ij/download.htlm). Afterwards, the placentas were sent for pathology.The first placenta was from an MC monoamniotic twin pregnancy in a 32-year-old para 4 gravida 6. She was diagnosed with gestational diabetes, which was well controlled by dietary measures only. The pregnancy was uneventful until 28 weeks, when an unexpected demise of one twin was diagnosed. The surviving twin had no signs of anaemia and 3 weeks later neurosonography, and MRI did not show any ischemic-hypoxic brain lesions. Because of extensive cord entanglement and the risk of subsequent double demise, the patient consented to a fetoscopic cord transection, which was performed at 31 weeks without complications. Further ultrasound scans showed good fetal well-being with normal Doppler findings of the umbilical artery, ductus venosus, and middle cerebral artery. Estimated weight was at the 59th centile before the surgery and continued to follow this centile for the remainder of pregnancy. At 35 weeks, a boy was born vaginally in good condition with a birth weight of 2534 g (39th centile). He was admitted to the neonatal unit for respiratory support with continuous positive airway pressure (CPAP). A brain MRI on day 8 was normal. Macroscopic evaluation of the placenta sho...