Three-tiered fetal heart rate interpretation system and adverse neonatal and maternal outcomes: a systematic review and meta-analysis

Abstract

To evaluate the rate of adverse neonatal or maternal outcomes in parturients with fetal heart rate tracings (FHRT) categorized as I, II or, III within the last 30-120 minutes of delivery. Medline OVID, Scopus, Embase, CINAHL, and Clinicaltrials.gov databases were searched electronically up to May 2022, utilizing combinations of the relevant medical subject heading (MeSH) terms, keywords, and word variants that were considered suitable for the topic. Only observational studies of term infants reporting outcomes of interest with category I, II, or III FHRT, were included. The co-primary outcome was the rate of either Apgar score < 7 at 5 minutes or umbilical (UA) artery pH < 7.00. Secondary outcomes were divided into neonatal and maternal adverse outcomes. Quality assessment of the included studies was performed using the Newcastle-Ottawa Scale. Random-effect meta-analyses of proportions was used to estimate the pooled rates of each categorical outcome in FHRT category I, II, and III pattern, and random-effect head-to-head meta-analyses to directly compare FHRT category I vs. II and FHRT category II vs. III, expressing the results as summary odds ratio (OR) or as mean difference with relative 95% confidence interval (CI). Of the 671 articles reviewed, 3 publications met the inclusion criteria. Among them there were 47,648 singletons at > 37 weeks, FHRTs in the last 30-120 min before delivery were characterized in the following manner: category I in 27.0%, category II in 72.9%, and category III in 0.1%. A single study, rated as of poor quality, provided 82.1% of the data and it did not provide any data for category III FHR tracings. Compared to category I (0.74%), Apgar score < 7 at 5 min occurred significantly more often with category II (1.51%; OR 1.56, 95% CI 1.23, 1.99) and with category III (14.63%; OR 14.46; 95% CI 2.77-75.39); compared to category II, III also had a significantly higher likelihood of low Apgar at 5 min (OR 14.46; 95% 2.77-75.39). UA pH < 7.00 occurred at similar rate among those with category I versus II (0.08 versus 0.24%; OR 2.85; 95% CI 0.41, 19.55). Compared to category I, UA pH below 7.00 was significantly more common with category III (31.04%; OR 161.56; 95% CI 25.18-1036.42); likewise, compared to category II, category III had a significantly higher likelihood of pH < 7.00 (OR 42.29, 95% CI 14.29-125.10). Hypoxic-ischemic encephalopathy occurred with similar frequency in categories I and II (0 versus 0.81%; OR 5.86, 95% CI 0.75-45.89) but was significantly more common in category III (0 vs. 18.97%; OR 61.43, 95% CI 7.49, 503.50).Cesarean delivery occurred with similar frequency between category I (13.41%) and II (11.92%; OR 0.87, 95% CI 0.72-1.05) but was significantly more common with category III (14.28%; OR 3.97, 95% CI 1.62-9.75); compare to category II, cesarean delivery was more common with category III (OR 4.55, 95% CI 1.88-11.01). Though Apgar score < 7 at 5 min and UA pH < 7.00 increases significantly from Category I to III of FHRT, about 98% of newborns with category II tracing do not have these adverse outcomes. The three-tiered FHR interpretation system provides an approximate but imprecise measurement of neonatal prognosis.