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

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.