Objective: To evaluate the performance of fetal scalp stimulation (FSS) compared to fetal blood sampling (FBS) as a second line test of fetal wellbeing in labor.
Study design: A prospective cohort study was conducted including 298 fetal blood sampling procedures performed due to abnormal fetal cardiotocography (CTG). Two independent observers interpreted the CTG following stimulation. The FSS test was classified as normal when an elicited acceleration and/or provoked fetal heart rate variability was recorded. The FBS was classified as normal (pH ≥7.25), borderline (pH 7.21-7.24), and abnormal (pH ≤7.20).
Results: Of the 298 procedures, 249 (84%) had a normal scalp pH result, 199 (67%) had an acceleration in response to FSS and 255 (86%) had an acceleration or normal variability in response to FSS. All 11 of the neonates classified as normal by FSS, but abnormal by FBS were born with normal Apgar scores and cord pH results. The consistency between FSS and FBS was "fair" (kappa 0.28) while the consistency between either test and cord arterial pH was "poor".
Conclusions: This study suggests that FSS has the potential to be a reliable alternative to FBS. The findings require evaluation in a well-designed randomized controlled trial.
Keywords: Fetal scalp stimulation; cardiotocography; fetal blood sampling; labor.