Fetal heart rate evolution and brain imaging findings in preterm infants with severe cerebral palsy

Abstract

Background: Cerebral palsy is more common among preterm infants than among full-term infants. Although there is still no clear evidence that fetal heart rate monitoring effectively reduces cerebral palsy incidence, it is helpful to estimate the timing of brain injury leading to cerebral palsy and the causal relationship with delivery based on the fetal heart rate evolution patterns. Understanding the relationship between the timing and the type of brain injury can help to identify preventive measures in obstetrical care.

Objective: This study aimed to examine the relationship between the timing of insults and the type of brain injury in preterm infants with severe cerebral palsy.

Study design: This longitudinal study was based on a nationwide database for cerebral palsy. The data of infants with severe cerebral palsy (equivalent to levels 3-5 of the Gross Motor Function Classification System-Expanded and Revised), born between 2009 and 2014 at 28 to 33 weeks of gestation, were included. The intrapartum fetal heart rate evolution patterns were evaluated by 3 obstetricians blinded to clinical information other than gestational age at birth, and these were categorized after agreement by at least 2 of the 3 reviewers into (1) continuous bradycardia, (2) persistently nonreassuring (prenatal onset), (3) reassuring-prolonged deceleration, (4) Hon's pattern (intrapartum onset), (5) persistently reassuring (pre- or postnatal onset), and (6) unclassified. Infant brain magnetic resonance imaging findings at term-equivalent age were assessed by a pediatric neurologist blinded to the background details, except for gestational age at birth and corrected age at image acquisition, and these were categorized as (1) basal ganglia-thalamus, (2) white matter, (3) watershed cortex or subcortex, (4) stroke, (5) normal, and (6) unclassified based on the predominant site involved. The risk factors for the basal ganglia-thalamus group were compared with those of the combined white matter and watershed injuries group.

Results: Among 1593 infants with severe cerebral palsy, 231 were born at 28 to 33 weeks of gestation, and 140 met the eligibility criteria. Fetal heart rate evolution patterns were categorized as bradycardia (17% [24]); persistently nonreassuring (40% [56]); reassuring-prolonged deceleration (7% [10]); reassuring-Hon (6% [8]); persistently reassuring (7% [10]); and unclassified (23% [32]). Cerebral palsy was presumed to have an antenatal onset in 57% of infants and to have been caused by intrapartum insult in 13% of infants. Magnetic resonance imaging showed that 34% (n=48) of infants developed basal ganglia-thalamus-dominant brain injury. Of the remaining 92 infants, 43% (60) showed white matter injuries, 1% (1) showed watershed injuries, 4% (5) showed stroke, 1% (1) had normal findings, and 18% (25) had unclassified findings. Infants with continuous bradycardia (adjusted odds ratio, 1033.06; 95% confidence interval, 15.49-68,879.92) and persistently nonreassuring fetal heart rate patterns (61.20; 2.09-1793.12) had a significantly increased risk for basal ganglia-thalamus injury.

Conclusion: Severe cerebral palsy was presumed to have an antenatal onset in 57% of infants and to have been caused by intrapartum insult in only 13% of infants born at 28 to 33 weeks of gestation. Although the white matter-watershed injury was predominant in the study populations, severe acute hypoxia-ischemia may be an important prenatal etiology of severe cerebral palsy in preterm infants.

Keywords: basal ganglia; brain injuries; cardiotocograph; cerebral palsy; hypoxia-ischemia; infant; perinatal; preterm; thalamus; white matter.