Association of Fetal Heart Rate Baseline Change and Neonatal Outcomes

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.