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Intrapartum Resuscitation Interventions for Category II Fetal Heart Rate Tracings and Improvement to Category I


Reddy, Uma M.; Weiner, Steven J.; Saade, George R.; Varner, Michael W.; Blackwell, Sean C.; Thorp, John M., Jr.; Tita, Alan T. N.; Miller, Russell S.; Peaceman, Alan M.; & McKenna, David S., et al. (2021). Intrapartum Resuscitation Interventions for Category II Fetal Heart Rate Tracings and Improvement to Category I. Obstetrics & Gynecology, 138(3), 409-416. PMCID: PMC8506980


OBJECTIVE: To evaluate intrapartum resuscitation interventions and improvement in category II fetal heart rate (FHR) tracings.
METHODS: This secondary analysis of a randomized trial of intrapartum fetal electrocardiographic ST-segment analysis included all participants with category II FHR tracings undergoing intrauterine resuscitation: maternal oxygen, intravenous fluid bolus, amnioinfusion, or tocolytic administration. Fetal heart rate pattern-recognition software was used to confirm category II FHR tracings 30 minutes before intervention and to analyze the subsequent 60 minutes. The primary outcome was improvement to category I within 60 minutes. Secondary outcomes included FHR tracing improvement to category I 30-60 minutes after the intervention and composite neonatal outcome.
RESULTS: Of 11,108 randomized participants, 2,251 (20.3%) had at least one qualifying intervention for category II FHR tracings: 63.7% improved to category I within 60 minutes and 50.5% improved at 30-60 minutes. Only 3.4% underwent cesarean delivery and 4.1% an operative vaginal delivery for nonreassuring fetal status within 60 minutes after the intervention. Oxygen administration was the most common intervention (75.4%). Among American College of Obstetricians and Gynecologists-defined subgroups that received oxygen, the absent FHR accelerations and absent-minimal FHR variability subgroup (n=332) was more likely to convert to category I within 60 minutes than the FHR accelerations or "moderate FHR variability" subgroup (n=1,919) (77.0% vs 63.0%, odds ratio [OR] 2.0, 95% CI 1.4-2.7). The incidence of composite neonatal adverse outcome for category II tracings was 2.9% (95% CI 2.2-3.7%) overall; 2.8% (95% CI 2.0-3.8%) for improvement to category I within 60 minutes (n=1,433); and 3.2% (95% CI 2.1-4.6%) for no improvement within 60 minutes (n=818). However, the group with improvement had 29% lower odds for higher level neonatal care (11.8% vs 15.9%, OR 0.71, 95% CI 0.55-0.91).
CONCLUSION: Nearly two thirds of category II FHR tracings improved to category I within 60 minutes of intervention with a relatively low overall rate of the composite neonatal adverse outcome.


Reference Type

Journal Article

Year Published


Journal Title

Obstetrics & Gynecology


Reddy, Uma M.
Weiner, Steven J.
Saade, George R.
Varner, Michael W.
Blackwell, Sean C.
Thorp, John M., Jr.
Tita, Alan T. N.
Miller, Russell S.
Peaceman, Alan M.
McKenna, David S.
Chien, Edward K.
Rouse, Dwight J.
El-Sayed, Yasser Y.
Sorokin, Yoram
Caritis, Steve N., for the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) Maternal-Fetal Medicine Units (MFMU) Network

Article Type




Data Set/Study

STAN Trial


United States of America




Thorp - 0000-0002-9307-6690