Impact of fetal blood sampling on vaginal delivery and neonatal outcome in deliveries complicated by pathologic fetal heart rate: a population based cohort study

Abstract

Objective: To compare the impact of electronic fetal monitoring (EFM) alone vs. EFM with additional fetal blood sampling (FBS) in vaginal deliveries complicated by pathologic fetal heart rate (FHR).

Methods: All deliveries in Hesse between 1990 and 2000 were evaluated for participation in this study. Inclusion criteria comprised (1) pathologic fetal heart rate, (2) singleton pregnancy, (3) cephalic presentation, (4) vaginal delivery, and (5) gestational age at delivery of more than 35 weeks' gestation. In order to analyze the meaning of additional risk factors at birth for the effectiveness of FBS two subgroups were selected depending on the presence of additional risk factors at birth. To examine the impact of FBS in deliveries with pathologic FHR on the mode of delivery and on neonatal outcome, univariate regression analysis was performed and odds ratios (OR) and their corresponding 95% confidence intervals (95% CI) were calculated.

Results: The study population comprised 49,560 deliveries, among deliveries complicated by pathologic FHR, 26% underwent FBS. Deliveries with pathologic FHR and controlled by FBS, with no additional antepartum risk factors, were associated with an increase in spontaneous births OR 1.41 (95% CI 1.27-1.58), and in the presence of additional risk factors OR 1.24 (1.19-1.30). Short-term neonatal outcome parameters were characterized by a lower frequency of severe fetal acidosis (umbilical artery pH <7.0) OR 0.55 (0.42-0.72), and Apgar score <5 after 5 min, OR 0.71 (0.55-0.90).

Conclusion: In vaginal deliveries with pathologic FHR the use of FBS as an additional means of intrapartum fetal surveillance is associated with less vaginal operative deliveries, and with an improved short-term neonatal outcome.