Protocol-Based Management of Severe Fetomaternal Hemorrhage (1.6 g/dL Hb) Allowing Term Vaginal Delivery

Introduction Fetomaternal hemorrhage (FMH), the transfer of fetal blood into maternal circulation, ranges from silent microtransfusions to massive bleeds causing anemia, hydrops, stillbirth, or neonatal death. While small FMH (30 mL) has a perinatal mortality rate of up to 5% in otherwise unexplained fetal deaths. Most FMH-related deaths occurred at term (74% between 37+0 and 41+0 weeks), which is significantly more often than in the case of other causes of stillbirth (O’Leary et al. Acta Obstet Gynecol Scand 2015; 94: 1354–1358). Antenatal suspicion arises most frequently from maternal reports of diminished or absent fetal movements, sinusoidal or non-reassuring cardiotocographic patterns, or newly detected hydrops on ultrasound (Amann et al. Ultraschall in Med 2011; 32 Suppl 2: E134–140). Doppler assessment of the middle cerebral artery peak systolic velocity (MCA-PSV ≥ 1.5 MoM) serves as a rapid, noninvasive surrogate for moderate-to-severe fetal anemia Bahlmann et al. J Perinat Med 2002; 30: 490–501). Definitive diagnosis uses quantitative assays: Kleihauer–Betke test, increasingly flow cytometry for fetal cell counts, and cordocentesis to confirm anemia (Wylie & D’Alton Obstet Gynecol 2010; 115: 1039–1051; Siemer et al. Ultraschall in Med 2010; 31: 192–194). Publication History Received: 08 August 2025 Accepted after revision: 11 December 2025 Article published online: 10 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany