Correlation between Intrapartum Cardiotocogram Findings and Cord Blood pH in Term and Preterm Labours Abstract

Sarah SC CHAN, William WK TO

Objectives:
To compare the correlation between abnormal intrapartum cardiotocogram findings and cord arterial blood pH values in high-risk labours that occurred before and after 34 weeks’ gestation.

Methods:
Data from preterm labours of singleton pregnancies of between 24 and 34 weeks’ gestation (preterm group) were retrospectively collected over a 36-month period and were compared with high-risk labours that occurred at or after 34 weeks’ gestation (term group) during the same period. The incidence of abnormal cardiotocogram findings (scored using the Royal College of Obstetricians and Gynaecologists 2001 guidelines), immediate pregnancy outcomes, and cord arterial blood pH values at delivery, were compared.

Results:
Data from a total of 68 preterm labours were compared with those from 128 matched term high-risk labours. Suspicious cardiotocograms were more common in the preterm group than in the term group (31% vs 9%; p<0.001) while pathological cardiotocogram patterns were more common in the term group as compared to the preterm group (22% vs 7%; p<0.025). Despite the higher incidence of pathological patterns in the term group, the incidence of a low cord arterial blood pH value below 7.15 was higher in the preterm group (9%) than the term group (2%) [p<0.05].

Conclusion:
The correlation between abnormal intrapartum cardiotocogram patterns and cord blood pH appeared to be different in term and preterm fetuses. The correlation with low cord blood pH was apparently better in term fetuses than in preterm ones.

Hong Kong J Gynaecol Obstet Midwifery 2009; 9:36-42

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