Earlier and improved screening for impending fetal compromise

Mark I. Evans, David W. Britt, Robert D. Eden, Shara M. Evans, Barry S. Schifrin

Research output: Contribution to journalArticlepeer-review

8 Scopus citations


Objective: The use of pH and base excess (FSSPHBE) from fetal scalp sampling (FSS) was abandoned when cardiotocography (CTG) was believed to be sufficiently accurate to direct patient management. We sought to understand the fetus’ tolerance to stress in the 1st stage of labor and to develop a better and earlier screening test for its risk for developing acidosis. To do so, we investigated sequential changes in fetal pH and BE obtained from FSS in the 1st stage of labor as part of a research protocol from the 1970s. We then examined the utility of multiple of the median (MoM’s) conversion of BE and pH values, and the capacity of Fetal Reserve Index (FRI) scores to be a proxy for such changes. We then sought to examine the predictive capacity of 1st stage FRI and its change over the course of the first stage of labor for the subsequent development of acidosis risk in the 2nd stage of labor. Methods: Using a retrospective research database evaluation, we evaluated FSSPHBE data from 475 high-risk parturients monitored in labor and their neonates for 1 h postpartum. We categorized specimens according to cervical dilatation (CxD) at the time of FSSPHBE and developed non-parametric, multiples of the median (MOMs) assessments. FRI scores and their change over time were used as predictors of FSSPHBE. Our main outcome measures were the changes in BE and pH at different cervical dilatations (CxD) and acidosis risk in the early 2nd stage of labor. Results: FSSPHBE worsens over the course of the 1st stage. The implications of any given BE are very different depending upon CxD. At 9 cm, −8 Mmol/L is 1.1 MOM; at 3 cm, it would be 2.0 MOM. The FRI level and its trajectory provide a 1st stage screening tool for acidosis risk in the second stage. Conclusions: Fetal acid-base balance (“reserve”) deteriorates beginning early in the 1st stage of labor, irrespective of whether the fetus reaches a critical threshold of concern for actual acidosis. The use of MoM’s logic improves appreciation of such information. The FRI and its trajectory reasonably approximate the trajectory of the FSSPHBE and appears to be a suitable screening test for early deterioration and for earlier interventions to keep the fetus out of trouble rather than wait until high risk status develops.

Original languageEnglish
Pages (from-to)2895-2903
Number of pages9
JournalJournal of Maternal-Fetal and Neonatal Medicine
Issue number15
StatePublished - 2022


  • 1st stage of labor
  • ACOG Category system
  • Electronic fetal monitoring
  • base excess
  • cardiotocography
  • cerebral palsy
  • fetal reserve index
  • fetal scalp sampling
  • metabolic acidosis
  • multiples of the median (MOMs)
  • pH
  • screening test


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