Abstract
Cesarean birth needs emergency coding according to the severity of the fetal or maternal condition at risk. For this purpose, many obstetricians use electronic fetal heart rate (FHR) monitoring to estimate the fetal acid-base balance. The emergency code decided upon by the attending obstetrician should be matched well with that of the anesthesiologist for the best neonatal outcome. To establish inter-professional understandings of emergency coding for cesarean births, I would like to provide some fundamentals on fetal physiology as background to understanding some FHR monitoring patterns.
A simple 3-tier classification has been widely accepted: normal (normal rate, normal variability, and no deceleration), abnormal (absent variability with decelerations or bradycardia), and intermediate. The majority of clinical cases belong to the intermediate group in which the temporal changes of the 4 FHR parameters (baseline, baseline variability, acceleration, and deceleration) are important in assessing the fetal acid-base balance. Among them, decreased variability and loss of acceleration are markers to suggest that the fetus is approaching borderline acidemia (pH=7.2). Decelerations also play central roles in FHR interpretation. Some important animal experiments and clinical evidence are presented.
