Association between Intrapartum Cardiotocography and Umbilical Cord Blood pH in Term Pregnancies: A Cross-sectional Study in a Tertiary Care Centre, Kolkata, India

Introduction: Labour, a physiological process for majority of foetuses, often acts as a challenge to foetal reserves causing foetal hypoxia. Foetal monitoring with intrapartum cardiotocography is an important tool to enable timely intervention to reduce adverse neonatal outcomes like postnatal cerebral palsy.

Aim: To determine an association between cardiotocography tracing and umbilical artery cord blood pH in term pregnancies in labour where the influence of drugs and the presence of other co-morbid medical/obstetric adverse outcomes have been ruled out.

Materials and Methods: This cross-sectional, hospital-based, observational study involved singleton uncomplicated term pregnancies with a normal baseline cardiotocography and spontaneous labour onset and progression admitted to the Labour Ward of the Department of Obstetrics and Gynaecology, of R.G. Kar Medical College and Hospital, Kolkata, West Bengal, India. Intrapartum continuous cardiotocography traces were recorded and those showing abnormal traces were documented and delivery expedited within two hours. Total of 90 such consecutive women were included in the study and umbilical arterial cord blood sample was taken for all these pregnancies immediate postpartum. Cardiotocography traces were then statistically compared with cord blood parameters and the findings were computed using Statistical Package for the Social Sciences (SPSS) software version 22.0.

Results: Out of 90 participants, the mean age was 24.21±3.43 years, most (43, 47.8%) of them were in between 21 to 25 years. Of the abnormal traces, 51 (56.7%) were NICE Category II (suspicious) and 39 (43.3%) were NICE category III (pathological). Cord blood analysis revealed that 40% had a pH value <7.0, 44.4% had blood lactate levels above 6 mmol/L and another 47.7% had a base deficit ≥12 mmol/L. On cross-tabulation and Chi-square analysis, these were all found to be statistically significant (p-value <0.05). Abnormalities of Foetal Heart Rate (FHR) and baseline variability had higher Odds ratio of predicting umbilical artery acidemia with Odd’s ratio for baseline variability abnormality as high as 2.768.

Conclusion: Although there has been a rising trend towards operative deliveries, the overall incidence of neonatal morbidity due to cerebral palsy is still on the rise. Cardiotocography can be a very important tool to identify neonatal acidosis in “at risk” foetuses and helps in timely intervention giving long term best outcomes.