Abnormal fetal heart rate tracing patterns during the first stage of labor: Effect on perinatal outcome

OBJECTIVE: The purpose of this study was to evaluate perinatal outcomes of infants who had pathologic fetal heart rate tracings during the first stage of labor, in comparison with pregnancies with normal tracings. STUDY DESIGN: The perinatal outcomes of 301 infants born at 37 to 42 weeks of gestation with pathologic fetal heart rate patterns during the first sta ge of labor were compared with 300 infants with normal fetal heart rate tra cing patterns. The data were collected prospectively. Tracings were interpr eted with the use of the National Institute of Child Health and Human Devel opment fetal heart rate monitor guidelines. RESULTS: Hydramnios (odds ratio, 7.68; 95% Cl, 1.75%-33.63%), oligohydramni os (odds ratio, 2.74; 95% Cl, 1.01 %-7.39%), and the presence of meconium-s tained amniotic fluid (odds ratio, 1.91; 95% Cl, 1.03%-3.3%) were independe nt factors that were associated with pathologic fetal heart rate monitoring during the first stage of labor in a multivariable analysis. The occurrenc es of umbilical arterial pH of <7.20, a 1 -minute Apgar score of <7, a base deficit of 12 mmol/L or higher, and operative deliveries were significantl y higher in the study group as compared with subjects with normal fetal hea rt rate monitoring. Late decelerations and severe variable decelerations (< 70 bpm) during the first stage of labor were independent risk factors (odd s ratio, 17.5; 95% Cl, 1.61%-185.7% and odds ratio, 3.9; 95% Cl, 1.36%-11.7 %, respectively) that were associated with fetal acidosis (determined by bo th pH of <7.2 and a base deficit of 12 mmol/L or higher) in a multiple logi stic model, controlled for hydramnios, oligohydramnios, meconium-stained am niotic fluid, augmentation by oxytocin, nulliparity, duration of first stag e of labor, and birth weight. CONCLUSION: The operative delivery rate was higher among patients with abno rmal first-stage fetal heart rate patterns. Late decelerations and severe v ariable decelerations were significant factors associated with fetal acidos is.