Intrapartum transperineal ultrasound for evaluating uterine contraction intensity in the second stage of labor

Purpose

To clarify whether intrapartum transperineal ultrasound (ITU) can be used to evaluate uterine contraction intensity, and whether the intensity is associated with the duration of the second stage.

Methods

A prospective observational study was performed involving 86 women with a normal singleton term fetus and more than three contractions every 10 min. ITU was performed for contractile and non-contractile periods of labor at the beginning of the second stage, and one representative “angle of progression (AoP)” image was selected for each period. The Mann–Whitney U test was used to compare ?AoP, the difference between the two angles, depending on the duration of the second stage. Receiver operating characteristic curves were used to evaluate the probability of duration of the second stage ≤50 min in nulliparous women.

Results

Among nulliparous women, ΔAoP differed significantly according to the duration of the second stage (52.5° ± 5.0° for ≤50 min vs. 30.9° ± 2.1° for >50 min; P < 0.001). Receiver operating characteristic curve analysis showed that approximately 85% of nulliparous women with ΔAoP greater than 40° delivered within 50 min.

Conclusion

These findings could be utilized in the evaluation of uterine contraction intensity, and ?AoP measurement could be used to predict the duration of the second stage of labor in nulliparous women.