(262) Fetal Heart Rate Tracing Characteristics Among Preterm Birth at 22.0-31.6 Weeks and Adverse Neonatal Outcomes

Objective: There is a paucity of evidence on the characteristics and significance of fetal heart rate tracings (FHRT) in the very preterm (22.0-31.6 weeks) period. We sought to address this and the associated neonatal outcomes.

Study Design: A retrospective review of all deliveries from January to December 2023 at a tertiary referral hospital. Criteria for inclusion were non-anomalous singleton deliveries at 22.0-31.6 weeks, where at least 10 minutes of FHRT was available, and neonatal resuscitation was initiated. A physician—blinded to all outcomes—reviewed the FHRT (0-120 min proximal to delivery, at 20 min epochs), and outcome data was obtained from chart review. The primary outcome was long term neonatal morbidity or mortality (LTNMM); the secondary outcomes were 5-min Apgar score of 4-6 and short-term neonatal morbidity or mortality (STNMM). Descriptive statistics with 95% confidence intervals (CI) were calculated with non-overlapping CI as significant.

Results: Among the 6,521 deliveries, 169 (2%) occurred at 22.0-31.6 weeks, of which 99 (58%) met the inclusion criteria. Intrapartum magnesium sulfate was administered in 97% of deliveries and antenatal corticosteroids in 98%. Moderate variability preceded delivery in 37.9% (95% CI 28.2-48.7%) of those with LTNMM; in 14.9% (95% CI 8.8-24.2%) of those with a 5-min Apgar score of 4-6; in 42.6% (95% 32.5 to 53.2%) of those with STNMM. Individuals with all types of decelerations – variable, late, and prolonged – had overlapping CI for all outcomes (Table 1). There were no cases of bradycardia or sinusoidal rhythm. Of the 38 newborns who met criteria for LTNMM, 20 (52.6%) also experienced STNMM while only 8 (21.1%) had Apgar of 4-6 at 5 min (Fig 1).

Conclusion: Among newborns delivered at 22.0-31.6 weeks, the likelihood of Apgar score 4-6 at 5 minutes and short- or long-term morbidity or mortality were similar irrespective of presence of moderate variability or decelerations. If confirmed, the reliance on moderate variability as a reassuring aspect to identify neonatal well-being at 22.0 to 31.6 weeks should be revisited.