Background: Fetal surveillance in labour is performed mostly to identify fetuses at risk of hypoxia in order to reduce neonatal morbidity and mortality by initiating timely intervention. While normal and abnormal fetal heart rate (FHR) patterns have been well recognised and characterized for the first stage of labour, FHR patterns during the second stage of labour commonly showed some forms of abnormalities leading to problems in interpretation, particularly in predicting fetal hypoxia and acidosis. This study aims to identify patterns of FHR tracing during the second stage of labour associated with neonatal acidosis. Methods: A prospective cross sectional study was conducted in the Labour Ward of a state referral hospital. The study population were patients with low-risk
singleton pregnancies between 37 to 42 weeks gestation who had normal cardiotocograph (CTG) tracing in the first stage of labour. CTG was recorded during the second stage of labour and neonatal umbilical cord blood was obtained for acid-base analysis immediately after birth prior to the delivery of placenta. FHR patterns were grouped according to modified Melchior and Barnard’s
classification and matched with neonatal acid-base status. Patients with normal FHR pattern in the second stage acted as control. Results: A total of 111 matched pairs were analysed. Ninety nine (89.2%) second stage FHR tracings showed abnormal features when compared to control. There were significantly more neonatal acidosis and hypercapnia in type 1b, type 2a, type 2b and type 3 CTG patterns compared to control, in increasing order of severity. In addition, types 2b and 3 showed significant difference in the base excess. Conclusion: Certain second stage fetal heart rate
patterns were found to be associated with neonatal acidosis.