Comparison of five classification systems for interpreting eletronic fetal monitoring in predicting neonatal status at birth

OBJECTIVE: The aim of our study was to compare the accuracy of diagnosis of not normal cardiotocography (CTG) in predicting neonatal status at birth, as determined by umbilical cord ph using five different classification systems for interpreting electronic fetal monitoring (EFM). STUDY DESIGN: 43 CTG traces considered “not normal” in the last 30 minutes of labor from full term singleton patients were retrospectively interpreted by an expert obstetrical provider following five different classification systems: the one used in the Dublin fetal heart rate monitoring trial (DFHRM), RCOG Guidelines EFM; SOCG clinical practice guideline on fetal health surveillance, Parer & Ikeda framework, 2008 NICHHD on EFM. For each five classification system, specificity, sensibility, predictive positive and negative values in predicting neonatal outcome (umbilical cord ph 7.15) were calculated. Accuracy in the interpretation of EFM classification systems was also calculated (proportion of agreements).RESULTS: The Ph value was never 7. It was 7.15 in 13 (33%) cases. Using DFHRM or RCOG classifications no traces resulted normal. In contrast normal traces were found using SOCG (6 cases: 14%), Parer (11 cases: 26%) and NICHHD (4 cases: 9%) classification. When considering ph 7.15cut off, we observed the following sensitivity and specificity values: 1 and 0 (DFHRM); 1 and 0 (RCOG); 0,5 and 0 (SOGC); 0 and 0.8 (Parer & Ikeda); 0 and 1 (NICHHD). In almost one half of the cases CTG resulted non reassuring or suspicious (DFHRM), suspicious (RCOG), atypical (SOGC) or yellow (Parer & Ikeda). The percentage rices to 91% when adopting NICHHD (indeterminate). Proportion of agreements index ranged from 2.8 (RCOGParer & Ikeda) to 8.8 (RCOG-DFHRM). CONCLUSIONS: There is fair agreement in the interpretation of EFM classification systems. Parer & Ikeda and NICHHD classifications have a better specificity in detecting umbilical cord ph7.15, but Parer & Ikeda is the one that showed the best predictor value of low levels of umbilical cord ph.