(727) Three-Tiered Fetal Heart Rate Interpretation System and Adverse Outcomes: A Systematic Review and Meta-Analysis

Per ACOG guidelines, a three-tiered interpretation (category I, II or III) should be used for intrapartum fetal heart rate tracing (FHRT), though the associated adverse outcomes among the categories is sparse. The objective was to compare the rate of adverse neonatal and maternal outcomes among the categories in term neonates.

Study Design:

We included all observational studies (published by Sep 2021) describing adverse outcomes with the three categories. The co-primary outcomes were the rates of either Apgar score < 7 at 5 minutes or umbilical artery (UA) pH < 7.00. Secondary outcomes included adverse neonatal (e.g., seizure, death within 27 days) and maternal outcomes (e.g., transfusion). Random-effect meta-analyses of proportions was used to estimate each outcome's pooled rate in the three categories. Random-effect head-to-head meta-analyses was used to compare each outcome in categories I vs II, I vs III, and II vs III. Results were expressed as summary odds ratios or mean differences with a 95% confidence interval (CI). PROSPERO#CRD42021269360

Results:

Of 2,611 abstracts reviewed, 3 studies met inclusion criteria (N=47,648 singletons at >37 wks). FHRT interpretation was performed by nurses in 2 studies and by a physician in the third. Tracings within last 1 to 2 hrs., were interpreted as category I in 27.0%, II in 72.9%, and III in 0.1%. The rate of Apgar score < 7 at 5 min (0.65% for category I, 1.14% for II, and 13.46% for III) and UA pH < 7.00 (0.08% for category I, 0.22% for II, and 36.53% for III) increased with each category and varied significantly, albeit with wide 95% CI (Table 1). Though the rate of neonatal seizure did not differ, the rates of hypoxic-ischemic encephalopathy, need for hypothermic therapy, and neonatal death were significantly different between the groups. Cesarean birth rate differed between categories, while postpartum hemorrhage and transfusion rates did not (Table 2).

Conclusion:

While the odds of adverse neonatal outcomes are increased with category III, the absolute risks are low and 99% of newborns with category II and ~65% of category III do not have pH< 7.00.