Reconceptualizing Intrauterine Resuscitation and Its Short-Term Impact
Authors: Devoe Lawrence D , Britt David W , Macedonia Christian R , Worth Jaqueline M , Mussallli George M , Mondestin-Sorrentino Myriam , Evans Mark I 
Published: December 2024

Objective: Intrauterine resuscitation (IR) may be employed during labor to reduce emergency deliveries with concerns for fetal wellbeing emanating mostly from increased uterine contraction frequency and/or intensity. However, there is no standard definition of what constitutes IR and how its impact is assessed. Here, we have created two measures of relative IR effectiveness, determined over a two-hour time frame after Pitocin (PIT) was first initiated, and ask how fetal risk severity at the time of its initiation impacted IR effectiveness.
Study Design: We analyzed 118 patients receiving PIT who underwent IR at least once during labor. Retrospectively, we assessed risk levels using our Fetal Reserve Index version 2 (FRI v2) scores that were calculated in 20-minute timeframes. FRIv2 scores include various maternal, obstetric, and fetal risk factors, uterine contraction frequency and FHR baseline rate, variability, accelerations, and decelerations. We define 3 IR scenarios to assess relative IR effectiveness. [1] no reduction of PIT infusion rates (PIT), [2] decreased PIT infusion rates (DPIT), or [3] PIT turned off (PIT OFF). Maternal repositioning and oxygen administration are nearly universal across all types, and therefore are not considered in groupings. We then created three measures of IR effectiveness by classifying changes in FRI v2 scores over six 20-minute windows coincident with and following IR use as: (1) “Improvement” (FRI score improvement), (2) “Stabilization,” (no further decrease in FRI score) and (3) failure. We evaluated the relative effectiveness of the three PIT options, and to test whether the level of fetal risk at the time of IR initiation affected its short-term effectiveness, FRI v2 risk scores were assigned to one of three groups (Green [1.00-0.625]; Yellow [0.50-0.25]; Red 0.25-0.0]). Higher scores indicate lower risk. Statistical analysis was performed with ANOVA and t- tests.
Results: Overall, the first and/or the only initiation of IR resulted in improvement in 71% of cases and stabilization in 78% of cases. The remaining 22% were failures, meaning that the FRIv2 score in the 7th 20-minute period was lower than the score at the time of initiation. There were modest, but not statistically significant, differences in effectiveness (improvement or stabilization) by type of IR. There was a trend toward lower IR effectiveness of PIT OFF during IR initiation when compared to PIT continuation or decreased groups.
Conclusions: IR initiation or type did not vary significantly by retrospectively calculated levels of fetal risk showing that wide variation in clinician practices determine how IR was used. The FRI provides contextualization of FHR elements by adding maternal, fetal, and obstetric risk factors and increased uterine activity enables a more rigorous and reproducible approach to analysis of emerging fetal compromise and IR effectiveness. FRIv2 further improves its physiologic underpinnings. Thus, we propose a new approach to the overall assessment of IR practice.