Predictive value of fetal scalp pH and base excess for fetal acidosis and poor neonatal outcome

Abstract

Objective: The objective of this study is to assess retrospectively the predictive value of fetal scalp pH and base excess (BE) for fetal acidosis and poor neonatal outcome in term, low-risk, spontaneous deliveries with suspicious or pathological intrapartum cardiotocography (CTG) tracings.

Methods: Umbilical artery pH and BE values obtained immediately after delivery and Apgar score were the outcomes under consideration. Statistics included receiver-operating characteristic curve (ROC) and multiple logistic regression analysis.

Results: Four hundred and six deliveries were included in the study. Scalp pH < 7.20 predicted umbilical pH ≤7.1 with 64.3% sensitivity and 92.9% specificity (p < .001). The corresponding positive-predictive value (PPV) was 24.3% and the negative-predictive value (NPV) was 98.6%. Scalp BE ≤ −7 mmol/l (a cut-off value provided by ROC curve analysis) predicted Apgar score ≤ 7 at 5 min with 61.9% sensitivity and 91.7% specificity (p < .001). The corresponding PPV and NPV were 29.5 and 97.7%, respectively. Neither scalp pH nor BE was significantly associated with umbilical BE values. Infants with intrapartum BE ≤ −7 mmol/l were 30 times on an average more likely to get a low Apgar score, independently of intrapartum pH values.

Conclusion: Our study supports the consideration of both scalp pH and BE values, when fetal blood sampling (FBS) is used.

Keywords:

• Apgar score
• fetal blood sampling
• fetal blood sampling (FBS)
• fetal monitoring

Disclosure statement

The authors report no declarations of interest.