Intrapartum cardiotocography and its correlation with umbilical cord blood pH in term pregnancies: a prospective study

Abstract

Background: The purpose of intra-partum fetal monitoring is to identify early signs of developing hypoxia. Electronic fetal monitoring is performed using cardiotocograph, which is a paper record of the fetal heart rate (FHR) patterns plotted simultaneously in relation to uterine activity. In low resource settings umbilical cord artery blood gas analysis can provide important information about the foetuses exposed to intrapartum hypoxaemic events and can distinguish the infant at high risk for asphyxia and related sequelae. The aim of this study was to correlate intrapartum CTG findings with umbilical cord blood pH at birth in term pregnancies in labour and thus evaluate the success of CTG in predicting fetal acidosis during labour.Methods: The present study included 301 consecutive women with term singleton pregnancies in labour. Intrapartum CTG was taken and classified into normal (category I trace), indeterminate (category II trace) and abnormal (category III trace) according to NICHD 2008 Classification (Adapted by ACOG 2013). Umbilical cord arterial blood was taken immediately after birth, in a pre-heparinised syringe and sent to the laboratory for pH study to detect acidosis. Cord blood pH <7.2 was taken as acidosis and cord blood pH ≥7.2 was taken as normal.Results: In this study, 50.2% of the women had normal CTG, 36.5% had indeterminate CTG and 13.3% had abnormal CTG. 18.3 % of the babies had acidosis. Out of the subjects with abnormal intrapartum CTG, 52.5% had acidosis, of the subjects with normal intrapartum CTG trace, 7.3% had acidosis and of the 110 subjects with indeterminate intrapartum CTG, 22.7% had acidosis. A statistically significant association was found between intrapartum CTG and umbilical cord arterial pH (p <0.001).Conclusions: From the analysis of this study, it can be concluded that an abnormal CTG should be managed appropriately, without delay, in order to prevent acidosis in the neonate and adverse long-term sequelae. The obstetrician should be more vigilant in cases of indeterminate CTG tracings and monitor such labours closely.