Incidence of Intrapartum Abnormal Fetal Heart Rate Pattern in Siriraj Hospital

Abstract

Objectives: To determine the incidence of intrapartum abnormal fetal heart rate (FHR), possible associated factors and pregnancy outcomes.Materials and Methods: A total of 900 low-risk pregnant women were enrolled in this retrospective cohort study. Obstetric, labor and delivery data were collected. Incidence of intrapartum abnormal FHR pattern was determined, according to the National Institute of Child Health and Human Development (NICHD) classification. Comparisons were made between those with and without abnormal FHR pattern to evaluate possible associated factors and pregnancy outcomes.Results: Mean maternal age was 29.1 years, 55.7% were nulliparous, and mean gestational age at delivery was 38.1 weeks. Incidence of abnormal FHR pattern was 30.7% (30.3% and 0.4% in NICHD category II and III, respectively). Among these, 46.6% and 39.7% occurred in active and deceleration phase of labor, respectively. Univariate analysis showed that rate of abnormal FHR pattern was more common among nulliparous women (RR 1.22, 95% CI 1.003-1.5, p = 0.045). Cesarean delivery was required in 28.9% of cases with abnormal FHR pattern. Birth asphyxia was significantly more common among those with abnormal FHR pattern (7.2% vs. 3.7%, p = 0.016). Multivariate analysis demonstrated that only nulliparity was significantly associated with abnormal FHR pattern (adjusted OR 1.35, 95%CI 1.01-1.82, p = 0.045).Conclusion: Incidence of intrapartum abnormal FHR pattern was 30.7% and nulliparity was the only independent associated factor. The condition significantly increased the risk of birth asphyxia.

Keywords

• Abnormal fetal heart rate pattern
• electronic fetal monitoring
• incidence