Fetal distress evaluation using and analyzing the variables of antepartum computerized cardiotocography

In this study, we tried to establish cut-off values for more than one parameters of computerized cardiotocography (c CTG) in the prediction of fetal distress during labor, using a group of pregnant women with low-risk pregnancies.

A retrospective study was performed. Data were collected from 167 patients for measurements of fetal heart rate (FHR) variables and perinatal outcome. Computerized CTG was performed with an Oxford Sonicaid monitor with connection to a 8000 system for CTG spontaneous analysis. The following c CTG variables were considered: FHR, number of accelerations, the presence and the number of episodes of high and low variation, the number of decelerations, short-term variation (STV), peaks of contractions (per hour) and fetal movements assessed by maternal perception (per hour). Computerized CTG recordings started not earlier than the beginning of week 38 of gestation. Immediately after delivery, blood sample was collected from umbilical artery for umbilical artery blood gas analysis (UBGA). The main UBGA parameter in cord umbilical artery that was considered for analysis was pH. pH values<7.25 were considered as suspicious for acidemia and pH values>or=7.25 as normal.

Women suspicious for fetal distress during labor presented significantly lower fetal movements (P=0.026), accelerations (P=0.018), variability (P<0.001), number of high episodes (P<0.001), higher values of FHR baseline (P<0.001) and low episodes (P<0.001). Only the number of decelerations did not differ significantly between the two groups (P=0.545). The cut-off points of 5.00 for STV and 3.00 for high episodes were determined to classify women with fetal distress, which yielded high sensitivities (34 and 52%) and specificities (96.6 and 94.9%), with positive predictive values of 81.0 and 81.3% and negative predictive values of 77.4 and 82.2%, respectively.

In conclusion, we believe that not only STV but also other components of the cCTG, mainly the presence and the number of episodes of high variation, are related to pregnancy's outcome as measured by an umbilical artery pH.