Fetal scalp blood lactate during second stage of labor: determination of reference values and impact of obstetrical interventions

Abstract

Objective: To determine the reference interval of fetal scalp blood lactate during second stage of labor.

Material: Two hundred and fifty-three women in first stage of labor with a reassuring CTG were asked for permission to sample fetal scalp blood during second stage.

Results: In cases with reassuring CTG and five minute Apgar score ≥9, the mean lactate value (±2 SD) was 2.5 mmol/L (lower limit 1.1, higher limit 5.2). The lactate concentration was significantly higher among nulliparous and in cases with use of epidural or oxytocin (p <0.001). There was a moderate positive correlation between scalp lactate values and active pushing time. When parity, epidural, oxytocin and active pushing time were analyzed together, they had equal influence on lactate values (p <0.001). Higher lactate values were associated with intermediate/pathological CTG compared to normal CTG (p <0.001). There was no correlation to gestational age or birthweight (p = 0.72, respectively 0.43).

Conclusions: The reference interval of fetal scalp lactate during second stage is 1.1–5.2 mmol/L. Parity, use of epidural or oxytocin and the duration of pushing are associated to increased lactate concentration; however, we could not demonstrate any correlation to advancing gestational age or birthweight.

Keywords:

• Fetal monitoring
• fetal scalp blood sampling
• labor
• lactate
• oxytocin
• pH
• second stage

Acknowledgements

We are thankful to parturient, midwives and assistant nurses for their assistance.

Declaration of interest

The authors declare they have no conflicts of interest to disclose. The study was supported by grants from the Medical Faculty at Lund University, and Region Skåne, Sweden.