Oral Concurrent Session 5 - Clinical Obstetrics
Oral Concurrent Sessions
Nandini Raghuraman, MD, MSCI (she/her/hers)
Associate Professor
Washington University School of Medicine
Washington University School of Medicine, Missouri, United States
Antonina I. Frolova, MD, PhD (she/her/hers)
Assistant Professor of Ob&Gyn
Washington University School of Medicine
St. Louis, Missouri, United States
Megan L. Lawlor, MD (she/her/hers)
Asst Prof of Ob & Gyn
Washington University School of Medicine
St. Louis, Missouri, United States
Amanda C. Zofkie, MD
Assistant Professor
Washington University School of Medicine
St. Louis, Missouri, United States
Roxane Rampersad, MD
Washington University School of Medicine
St. Louis, Missouri, United States
Jeannie C. Kelly, MD, MS (she/her/hers)
Associate Professor
Washington University School of Medicine
Washington University School of Medicine, Missouri, United States
Steve Porter, MD
Clinical Instructor
Case Western Reserve University, University Hospitals MacDonald Women's Hospital
Cleveland, Ohio, United States
Susan Mann, MD
Assistant Professor
Beth Israel Deaconess Medical Center, Harvard Medical School
Boston, Massachusetts, United States
George A. Macones, MD, MS, MSCE
Chair & Professor, Department of Women’s Health
Department of Women’s Health, Dell Medical School at the University of Texas at Austin
Austin, Texas, United States
Alison G. Cahill, MD, MSCI
Assoc. Dean, Translational Research; Prof, Women’s Health; Dir, Health Transformation Research Inst.
Department of Women’s Health, Dell Medical School at the University of Texas at Austin
Department of Women’s Health, Dell Medical School at the University of Texas at Austin, Texas, United States
Although Category II (Cat II) fetal heart rate (FHR) tracings are considered indeterminate for predicting acidemia, little is known about risks of Cat II accumulation over time. We evaluated the association between the proportion of labor in Cat II and the risk of elevated umbilical artery (UA) lactate, a marker of fetal hypoxia and metabolic acidosis.
Study Design:
This retrospective cohort included all laboring patients from 3/2023–2/2025 with continuous FHR monitoring on a single unit with universal cord gases. FHR category was documented every 30 minutes in the EHR by bedside nurses and extracted via an integrated clinical decision support tool. The primary exposure was percent time in Cat II (Cat II %), defined as the duration of Cat II over the duration of labor, calculated overall and by labor phase. The outcome was elevated UA lactate (≥6.5 mmol/L). Multivariable logistic regression was used to estimate adjusted odds ratios (aORs) and predicted probabilities, adjusting for labor duration, nulliparity, and preterm birth. Stepwise models assessed cumulative associations across labor phases.
Results:
Among 4191 patients with EFM documentation and cord gases, 600 (14.3%) had an elevated UA lactate. Mean Cat II % was 42±33%. Increasing Cat II % was significantly associated with elevated UA lactate (p< 0.001). Predicted probabilities demonstrated a progressive rise in odds of elevated UA lactate as Cat II % increases. When examining Cat II % across labor phases, each 1% increase during the latent phase was associated with a 0.6% increase in odds (aOR 1.006, 95% CI 1.003–1.008); this association strengthened with the addition of Cat II in the active phase (aOR 1.008, 95% CI 1.006–1.011), and further with inclusion of the second stage (aOR 1.009, 95% CI 1.007–1.012), suggesting a cumulative association across labor.
Conclusion:
Higher Cat II % is independently associated with a small but significant increase in odds of elevated UA lactate. Findings across labor phases suggest that prolonged presence of Cat II may confer increasing risk.