Intrapartum fetal monitoring and perinatal risk factors of neonatal hypoxic-ischemic encephalopathy

Background: Neonatal hypoxic-ischemic encephalopathy (HIE) in term infants, is a major cause of neonatal mortality and severe neurologic disability.

Objectives: To identify in labor fetal monitoring characteristic patterns and perinatal factors associated with neonatal HIE.

Study design: Single-center retrospective case-control study between 2010 and 2017. Cases clinically diagnosed with neonatal HIE treated by therapeutic hypothermia according to strict criteria (HIE-TH) were compared to a group of neonates born in the same period, gestational age-matched diagnosed with fetal distress according to fetal monitoring interpretation that was followed by prompt delivery, without subsequent HIE or therapeutic hypothermia (No-HIE). The primary outcome of the study was the electronic fetal monitoring (EFM) pattern during 60 min prior to delivery; the secondary outcome was the identification of perinatal associated factors.

Results: 54 neonates with HIE were treated by therapeutic hypothermia. EFM parameters most predictive of HIE-TH were indeterminate baseline heart rate OR = 47.297, 95% (8.17-273.76) p < 0.001, bradycardia OR = 15.997 95% (4.18-61.18) p < 0.001, low variability OR = 10.224, 95% (2.71-38.45) p < 0.001, higher baseline of the fetal heart rate calculated for each increment of 1 BPM OR = 1.0547, 95% (1.001-1.116) p = 0.047. Rupture of a previous uterine cesarean scar and placental abruption were characteristic of the HIE-TH group 14.8% vs. 1% p < 0.05; and 16.7% vs. 6% p < 0.05, respectively. Adverse neonatal outcomes also differed significantly: HIE-TH had a higher rate of neonatal seizures 46.2% vs. 0% p < 0.001 and mortality 7.7% vs. 0% p < 0.001.

Conclusions: Characteristic fetal monitoring pattern prior to delivery together with acute obstetric emergency events are associated with neonatal HIE, neurological morbidity, and mortality.

Keywords: Bradycardia; Indeterminate baseline heart; Low variability; Obstetric emergency; Perinatal hypoxia; Placental abruption; Tachysystole; Uterine rupture.