Determination of the timing of fetal brain damage from hypoxemia-ischemia

Objective: This study analyzed the cases of 55 children with cerebral palsy to evaluate methods for determination of the time before birth at which antenatal hypoxemia-ischemia damaged the brain. Study Design: In primate fetuses persistent fetal bradycardia develops close to the time that hypoxemia-ischemia damages basal ganglia structures in the brain. The same proved true in children in this study, so this time was thereafter used as a baseline to test the values of other proposed timers of hypoxemicischemic brain damage. Results: Basal ganglia lesions predominated when bradycardia lasted <30 minutes before birth. As the bradycardia duration lengthened, white matter and eventually watershed brain lesions predominated. Lymphocytosis appeared 25 minutes after the bradycardia began, and thrombocytopenia appeared at 20 to 28 hours. The lymphocytosis disappeared 14 to 18 hours after it first appeared. Conclusions: Counting back from the time that lymphocytosis ended and thrombocytopenia began can sometimes identify the time when hypoxemia-ischemia damaged the fetal brain. (Am J Obstet Gynecol 2001;184:217-24.)