The Incidence of Large Fetomaternal Hemorrhage and the Kleihauer-Betke Test

Abstract

To assess the frequency of large fetomaternal hemorrhage and to estimate its incidence in cesarean compared with vaginal deliveries. In this prospective cohort study, the study group was composed of 313 women who underwent cesarean delivery. Control subjects were 253 women who delivered vaginally and were matched for age, parity, ethnic origin, and gestational age. Ninety-six pregnant women at term, but before delivery (prelabor group), were also included to determine whether delivery itself is the cause of fetomaternal hemorrhage. Fetomaternal hemorrhage was measured by using the Kleihauer-Betke test. Twenty women (6.4%) in the study group and 17 (6.7%) in the control group had a large fetomaternal hemorrhage (Kleihauer-Betke test > 0.4%). Five women (5.2%) in the prelabor group had a large fetomaternal hemorrhage. The differences were not significant. A large fetomaternal hemorrhage occurred in 14 of 146 (9.6%) women who underwent emergency cesarean, compared with 6 of 167 (3.5%) who delivered by elective cesarean (P = .04). In deliveries complicated by oligohydramnios, cord around the neck, or low birth weight, a higher rate of large fetomaternal hemorrhage was seen. Our results indicate a rate of large fetomaternal hemorrhage that is substantially higher than previously reported, with no difference between vaginal and cesarean deliveries. This may reflect inaccuracies with the current method used to estimate the degree of fetomaternal hemorrhage.