249: Deceleration area-time ratio as predictor of acidemia in fetuses with early onset growth restriction

Abstract

There is little existing literature to guide the interpretation of fetal heart rate tracings in growth restricted fetuses with abnormal Doppler studies remote from term. This study sought to determine fetal heart rate parameters associated with fetal acidemia. Data was collected prospectively on 14 pregnancies diagnosed with early-onset intrauterine growth restriction with abnormal umbilical artery Dopplers. All women included in this analysis delivered at less than 32 weeks gestation and had an umbilical artery pH obtained at time of delivery. An investigator blinded to the umbilical cord pH analyzed the last 60 minutes of fetal heart rate tracing prior to delivery and recorded baseline, variability, presence of accelerations, number of decelerations, maximum depth of deceleration, total time spent in deceleration, and total deceleration area (TDA). TDA was defined as area below the fetal baseline in units of 10 beats per 10 seconds. From these data, the ratio of TDA over total deceleration time (TDA/time) was calculated (see Figure 1). Receiver operating characteristic (ROC) curves were used to analyze the ability of each of these parameters to predict umbilical cord pH less than 7.00 and less than 7.10. A p-value < .05 was considered significant. Of the 14 women, 2 had umbilical cord pH values less than 7.00 and 5 with pH less than 7.10. The area under the curve for TDA-time ratio was 1.00 for pH less than 7.00 and .80 for pH less than 7.10. The areas under the curve showed poor predictive value of maximum depth of decelerations, number of decelerations, time spent in deceleration, and TDA (Table 1). A TDA/time cut-off of .15 had a 100% specificity and sensitivity for predicting pH less than 7.0 and a 100% specificity and 40% sensitivity for predicting pH less than 7.10. In this cohort, the TDA/time ratio was the strongest predictor of an abnormal umbilical artery pH, suggesting long, shallow decelerations are of greatest concern in these patients. This represents a novel technique for quantifying these decelerations.View Large Image Figure ViewerDownload Hi-res image Download (PPT)