(272) Accelerations or Variable Decelerations Among Preterm Birth at 22.0-31.6 Weeks: Associated Neonatal Composite Adverse Outcomes

There is a paucity of data on the association of adverse neonatal outcomes with accelerations or variable decelerations in fetal heart rate tracings (FHRT) in the very preterm (22.0-31.6 weeks) period. We sought to address this knowledge gap.


Study Design:

A retrospective review of all deliveries (Jan to Dec 2023) at a tertiary hospital. Inclusion criteria were non-anomalous singletons delivered at 22.0-31.6 weeks, where at least 10 minutes of FHRT was available, and neonatal resuscitation was initiated. An obstetrician—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 short-term neonatal morbidity or mortality (STNMM); the secondary outcome was long-term neonatal morbidity or mortality (LTNMM). 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%. Accelerations of any type were present in 61% (95% CI 51-71%) of FHRT. Accelerations of 10x10 beats per minute (BPM) occurred in 41% (95% CI 31-52%) of FHRT and were associated with a significantly lower likelihood of STNMM (32%; 95% CI 18-48%) than no acceleration (74%; 95% CI 54-89%). Variable decelerations occurred in 59% (95% CI 48-68%), and the likelihood of STNMM was similar for those without deceleration. The LTNMM did not significantly differ among those with or without accelerations, nor those with and without variable decelerations (Table 1).


Conclusion:
Among singletons delivered at 22.0-31.6 weeks, accelerations and variable decelerations occur in the majority, and while accelerations of at least 10x10 bpm significantly lowered the likelihood of STNMM, they are not associated with LTNMM. The presence of variable decelerations was not associated with STNMM or LTNMM.