369: Impact of amnioinfusion on uterine tone and contractions

Abstract

We sought to assess whether the use of amnioinfusion (AI) during the first stage of labor impacts contraction pattern and uterine tone. We performed a secondary analysis of laboring women within a prospective cohort study of all consecutive births at or beyond 37 weeks. Formally trained obstetric nurses blinded to clinical data and outcome evaluated the contraction patterns of 200 women in the 60 minutes following initiation of AI for Category II tracings with recurrent variable decelerations. The primary outcomes were changes in frequency of contractions, rates of tachysystole, average Montevideo units, and baseline tone compared between the first 30 minutes and the second 30 minutes following AI initiation. Of the 200 women who received an AI, the average contraction frequency was 11.6 (± 3.3) in the first 30 minutes and 11.5 in the second 30 minutes (± 3.3), which was not significantly different (p=0.80). Furthermore, there were no significant differences in rates of tachysystole (11.0% vs 8.5%, p=0.20), adequacy of uterine contractions, as defined by Montevideo units, (380.0 ± 420.8 vs 391.7 ± 443.8, p= 0.79), or mean uterine resting tone (21.2 ± 7.0 vs 21.7 ± 6.5, p=0.19). Our study suggests that after initiation of AI there were no significant differences in frequency or adequacy of uterine contracts, rates of tachysystole, or baseline uterine tone.