Predictive accuracy of intrapartum cardiotocography in terms of fetal acid base status at birth.

OBJECTIVE: To find out the predictive value of intrapartum Cardiotocograph (CTG) in terms of fetal acid base status at birth in women undergoing emergency caesarean section for a suboptimal CTG trace.

STUDY DESIGN: Observational study.

PLACE AND DURATION OF STUDY: At the MCH Centre, Pakistan Institute of Medical Sciences, Islamabad, from June 2004 to July 2005.

METHODOLOGY: All women undergoing emergency caesarean section for a suboptimal intrapartum CTG were recruited in the study. Immediately after the delivery of the baby a segment of umbilical cord was doubly clamped at a distance of 10 cm, and 2 ml of arterial cord blood was taken in a heparinized syringe for arterial blood gas indices analysis. All CTG tracings were reviewed using FIGO guidelines and compared for fetal arterial blood gas indices.

RESULTS: Of the 57 patients who underwent cesarean section due to suboptimal CTG, 51 (89%) had suspicious trace while 6 (11%) had pathological trace. Positive predictive value of CTG was 18% for fetal hypoxia, 21% for fetal hypercarbia., 26% for fetal acidosis and 37% for base excess. Predictive value of suspicious trace for similar blood indices was 13%, 13%, 17% and 35% respectively. For pathological trace, predictive value was 50%, 83 %, 100% and 66% and respectively.

CONCLUSION: Based on the results, it is concluded, that the suspicious CTG trace has low predictive value in terms of fetal acid base status at birth and needs to be complemented with other diagnostic modalities before undertaking any operative intervention. Pathological CTG on the other hand is highly predictive of fetal acidosis at birth warranting immediate intervention.