Electronic fetal monitoring: what's reassuring?

Background. To determine which combinations of fetal heart rate pattern abn ormalities are associated with normal outcome in term pregnancies. Methods. A cohort of 2200 consecutive deliveries was examined and the fetal heart rate tracings analyzed. Singleton, term patients without chorioamnio nitis or serious malformations were used to perform logistic regression ana lysis to select those FHR patterns associated with increased risk for Apgar <7 and cord pH<7.15, or immediate adverse outcome. Results. Patients having no fetal heart rate abnormalities, mild variable d ecelerations, decreased variability, mild bradycardia, or accelerations pre sent, constituted 84% of all fetal heart rate tracings. These tracings alon e, or in combination, predicted 5 minute Apgar score greater than or equal to 7 in 99.7%, cord pH greater than or equal to 7.15 in 96.9% and no advers e neonatal sequelae in 96.2% of cases. Accelerations were reassuring regard less of FHR pattern. When these patterns were not present, non-reassuring t racings, the risk for immediate adverse outcome increased 50%. The non-reas suring tracings were both without accelerations and had tachycardia, prolon ged bradycardia, severe variable or late decelerations, or a combination of these patterns. This increased risk was independent of the risk of confoun ders: i.e. thick meconium (1.8-fold), prolonged second stage of labor (>50 min., 1.5-fold), maternal disease (e.g. kidney, respiratory, 3-fold), or hy pertensive disease (1.9-fold). Conclusions. The great majority of fetal heart rate pattern abnormalities c an be considered reassuring as they are within normal variations of a healt hy fetus. The non-reassuring ones identify infants that truly require furth er evaluation by fetal scalp, vibroacoustic stimulation, or fetal scalp blo od sampling.