Abstract
Objective The objective of this study was to describe the incidence of baseline change within
normal range during labor and its prediction of neonatal outcomes.
Materials and Methods This was a prospective cohort of singleton, nonanomalous, term neonates with continuous
electronic fetal monitoring and normal baseline fetal heart rate throughout the last
2 hours of labor. We determined baseline in 10-minute segments using Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria. We evaluated baseline
changes of ≥ 20 and ≥ 30 bpm for association with acidemia (umbilical cord arterial
pH ≤ 7.10) and neonatal intensive care unit (NICU) admission. Finally, we performed
a sensitivity analysis of normal neonates, excluding those with acidemia, NICU admission,
or 5-minute Apgar < 4.
Results Among all neonates (n = 3,021), 1,267 (41.9%) had change ≥ 20 bpm; 272 (9.0%) had ≥ 30 bpm. Among normal
neonates (n = 2,939), 1,221 (41.5%) had change ≥20 bpm. Acidemia was not associated with baseline
change of any direction or magnitude. NICU admission was associated with decrease ≥ 20
bpm (adjusted odds ratio [aOR]: 2.93; 95% confidence interval [CI]: 1.19 – 7.21) or
any direction ≥ 20 bpm (aOR: 4.06; 95% CI: 1.46–11.29). For decrease ≥ 20 bpm, sensitivity
and specificity were 40.0 and 81.7%; for any direction ≥ 20 bpm, 75.0 and 58.3%.
Conclusion Changes of normal baseline are common in term labor and poorly predict morbidity,
regardless of direction or magnitude.
Keywords
baseline change - electronic fetal monitoring - neonatal outcome - neonatal acidemia
