ObjectiveTo assess the potential for recurrence of placental hemorrhagic endovasculitis and to identify clinical or pathologic cofactors that might influence recurrence of this lesion or subsequent pregnancy outcome.MethodsNinety-seven women with a placenta affected by hemorrhagic endovasculitis, who also had at least one placenta referred to the Michigan Placental Tissue Registry from a subsequent pregnancy, were identified from 10,531 referrals between 1978 and 1988. Histologic slides from 209 placentas and clinical data from 211 infants (two sets of twins) from initial (first) and subsequent referrals were analyzed. Placentas were graded for the presence, extent, and severity of hemorrhagic endovasculitis and chronic villitis of unknown etiology; for placental lesions indicative of hypertensive maternal vessel disease; and for intravascular nucleated erythrocytes and chorionic thrombi. Maternal data included age, gravidity, number of previous losses, and history of toxemia or hypertension. All data were analyzed for significance using χ2andttests. Outcome assessment was based on recurrence of hemorrhagic endovasculitis and infant viability with the second referral.ResultsWith first referrals, 80 of 98 infants (81.6%) were stillborn. Among second referrals, 26 of 98 infants (26.5%) were stillborn. Hemorrhagic endovasculitis recurred in 28 second placentas (28.9%); of these, 18 infants (64.3%) were stillborn. Higher rates of recurrence were found with progressively higher first-referral chronic villitis severity scores (P< .02), higher hypertensive placental lesion scores (P< .001), and first referrals with a history of toxemia or hypertension (P< .02). Recurrence of hemorrhagic endovasculitis was higher in patients with two or more of these factors in first referrals (P< .001). Subsequent stillbirth was more frequent with progressively higher first-referral hypertensive placental lesion scores (P< .01) and in first placentas with two or more risk factors (P= .064). Hemorrhagic endovasculitis severity scores, intravascular nucleated erythrocytes, and chorionic thrombi were associated with stillbirth in index pregnancies only. Maternal age, gravidity, or history of prior losses were not predictive.ConclusionsPlacental hemorrhagic endovasculitis is associated with pregnancy loss and can recur in some patients. Interrelations among placental hemorrhagic endovasculitis, chronic villitis, maternal hypertension, and adverse outcomes in subsequent pregnancies are apparent. This information may be useful in patient counseling.