Introducing routine fetal scalp blood analysis (FSBA) for suspicious or pathologic fetal heart rate – effect on mode of delivery, fetal and maternal outcome

Introduction: Despite a good sensitivity (80 – 91%) for fetal hypoxia or acidosis, specificity of fetal heart rate (FHR) analysis is low (9 – 63%). Fetal scalp blood analysis (FSBA) is a complementary tool for the interpretation of pathologic FHR. However FSBA is an invasive procedure and could lead to complications.

In this study we investigated the effect of introducing FSBA as an additional tool used in clinical routine for non-reassuring FHR on fetal and maternal outcome.

Material and methods: In a retrospective single institution observational study all deliveries between 2006 and 2011 were reviewed. The analysis was restricted to deliveries with non-reassuring FHR during first or second stage of labour.

Results: There were 10371 deliveries at our institution between 2006 and 2011. 1228 deliveries fulfilled inclusion criteria. Non-reassuring FHR occurred in 11.8%.

Between 2006 and 2011 use of FSBA increased from 19% to 66%. Deliveries with FSBA ended in spontaneous deliveries in 36.5% (range 21 – 41%), in secondary C-sections in 39% (21 – 46%) and in instrumental deliveries in 22.5% (18 – 58%). In deliveries with non-reassuring FHR without FSBA secondary C-section rate was 80% and instrumental delivery rate 20%.

Fetuses monitored by FSBA had a significantly lower risk for postpartum acidosis as measured in umbilical artery blood samples. The routine use of FBA correlated with a decrease in secondary C-section rate for non-reassuring fetal heart rates by approximately 60% which translated into an overall decrease in secondary C-section rate by 3%.

Conclusion: FSBA for clarification of non-reassuring FHR was accompanied by a decrease in secondary C-sections.