Observation on validity of the five-tier system for fetal heart rate pattern interpretation proposed by Japan Society of Obstetricians and Gynecologists

Abstract

Objective: To evaluate the five-tier classification of fetal heart rate (FHR) tracings recently proposed by Japan Society of Obstetricians and Gynecologists (JSOG). Methods: The database between January and June 2009 was reviewed for women in active labor at ≥36 + 0 gestational weeks, with singleton fetuses in cephalic presentation and with umbilical artery blood gas analyses. Continuous FHR tracings were assessed according to the five-tier classification proposed by JSOG, where level 1 is normal, level 2 is subnormal and levels 3–5 are abnormal patterns. Results: A total of 341 parturient women were eligible for this study protocol. The median (range) of the levels in the first and the second stage of labor were 1 (1–4) and 2 (1–4), respectively (p < 0.001). Both pH and base excess of umbilical artery decreased with higher levels of FHR tracings interpretation (p < 0.01). Interventions resulting in delivery were more necessary in the first stage of labor than in the second stage of labor in cases of levels 3 and more. Conclusions: Five-tier system for FHR tracing interpretation proposed by JSOG intercorrelates with the fetal acid-base balance well. Categorization of FHR tracings by uniform diagnostic criteria will be useful to standardize therapeutic strategy by sharing common perception among obstetrical staff.