29: Predicting acidemia with intrapartum electronic fetal monitoring (EFM)


      The wide-spread use of EFM persists despite lacking evidence to demonstrate that patterns can predict acidemia. We aimed to estimate the ability of EFM patterns, alone and in combination, compared to the Category system to predict acidemia in term infants.

      Study Design

      This was a prospective cohort study of all consecutive women in labor at ≥ 37 weeks gestation with a singleton cephalic fetus between 2010-2014. Continuous EFM and arterial cord gas (ACG) were inclusion criteria, both universal at the study site. EFM patterns during the 2 hours prior to delivery were interpreted in 10-minute epochs by trained obstetric research nurses, blind to clinical data including pH, with previously published high reproducibility. Interpretation included the Category system, individual EFM patterns per the NICHD criteria and total deceleration area (each area = ½ depth x duration of deceleration, added over a given time). Final regression models adjusted for nulliparity, pregestational diabetes, and advanced maternal age. Area under the receiver-operator characteristic curves (AUC) was used to estimate and compare the predictive efficiency of EFM patterns


      Of 8,580 women in labor, 149 (1.7%) delivered infants with acidemia. Compared to the Category, combinations of EFM features were significantly more discriminatory for acidemia; specifically, baseline and deceleration features were the most predictive. The model with total deceleration area and tachycardia (AUC=0.759) and 1 or more prolonged and tachycardia (AUC=0.767) had the greatest predictive ability, followed by the model with number of decelerations and tachycardia (AUC=0.735). Category II (AUC=0.645) or Category III (AUC=0.613) alone had the lowest predictive ability (Table). Heart rate variability was not a significant predictor in multivariable analysis.


      Specific EFM patterns, alone and in combination, are superior to Category II or III alone in discriminating between term infants with acidemia and those without. Tachycardia combined with either prolonged decelerations or deceleration area in the 2 hours prior to delivery were the most efficient models.
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