Association of normal-range fetal heart rate variations during labor with umbilical cord arterial blood gas parameters and neonatal outcomes: A cross-sectional study.

Abstract

Background: Fetal heart rate (FHR) monitoring is a routine, non-invasive method for assessing fetal well-being during labor. However, its low sensitivity and high false-positive rate often lead to unnecessary cesarean deliveries. While fetal scalp blood sampling offers a more accurate assessment of intrauterine hypoxia, it is invasive, technically challenging, and prone to failure.

Objective: To evaluate the association between intrapartum FHR beat-to-beat variability (within the normal range) and umbilical cord arterial blood gas parameters, and to assess their predictive value for neonatal outcomes, such as Apgar scores and acidosis.

Materials and methods: This cross-sectional study reviewed medical records of all mothers who had delivered at Yas hospital, Tehran, Iran between August and December 2022. A total of 120 women with term, singleton pregnancies ( $\ge$ 37 wk) who were candidates for vaginal delivery were included. FHR monitoring was conducted on admission and 30 min before delivery. Umbilical cord arterial blood gas analysis was performed immediately after birth. Neonates were grouped based on cord pH $<$ 7.2 (acidosis) vs. $\ge$ 7.2 (non-acidosis).

Results: 17 neonates (14.2%) had pH $<$ 7.2. The acidosis group had significantly lower beat-to-beat variability at both time points (p = 0.002 and p $<$ 0.001) and greater variability reduction during labor (p $<$ 0.001). Cesarean rates and lower Apgar scores were significantly more frequent. Multiple regression analysis confirmed associations between reduced variability, neonatal acidosis, and lower Apgar scores.

Conclusion: Even within normal limits, reduced FHR variability may signal fetal compromise. Monitoring variability trends could enhance intrapartum care and neonatal outcomes.