Placental findings in feto-maternal hemorrhage in livebirth and stillbirth.

Feto-maternal hemorrhage (FMH) is not an uncommon event during pregnancy with important clinical implications for both maternal and fetal outcomes. The diagnosis is often made using Kleihauer-Betke (KB) test. As FMH occurs transplacentally, examination of the placenta may contribute to the diagnosis of FMH. This retrospective case-control study aims to examine the placental features associated FMH in patients with known positive KB test results. When compared with KB negative placentas (n=88), KB positive placentas (n=49) had significantly higher incidence of pallor (6/49 vs 0/88, p=0.0017), IVT (11/49 vs. 5/88, p=0.0032) and nRBCs (12/49 vs. 4/88, p=0.0008). Autopsy cases with fetal or neonatal death due to FMH, (n=13) compared to a cohort of 162 placentas associated with other, non-FMH causes of death also had significantly higher frequency of pallor (5/13 vs 0/162, p<0.0001), IVT (6/13 vs 24/162, p=0.011) and nRBCs (11/13 vs 67/162, p=0.003). Pallor and nRBC were also associated with higher volume of FMH. Placental parenchymal pallor, intervillous thrombi and presence of nRBCs are significantly associated with documented FMH in both normal pregnancies and pregnancies associated with fetal or neonatal death. The presence of these findings, especially in combination, may suggest the need for maternal KB testing to rule out FMH and neonatal monitoring and/or intervention.