Uterine electric activity during the third stage of labor; a look into the physiology of a deserted stage.

OBJECTIVE To evaluate uterine activity during the third stage of labor and compare it to that observed in the second stage of labor. STUDY DESIGN Uterine electric activity was prospectively measured using electrical uterine myography (EUM) in 44 women with singleton pregnancy at term during the final 30 min of the second stage and throughout the third stage of labor. Results are reported using a scoring index of 1-5 mWS (micro-Watt-Second). Patients were stratified into two groups based on the duration of the third stage (<15 min and >=15 min) RESULTS The mean durations of the second and third stages were 51.9 ± 63.5 and 15.4 ± 7.5 minutes, respectively. During the third stage, uterine activity (contractions peaks) was similar to that observed during the second stage of labor (3.43 ± 0.64 mWS versus 3.42 ± 0.57 mWS, p = 0.8). No correlation was found between the duration of the third stage and EUM measurements during the third (p = 0.9) or the second (p = 0.2) stages of labor. No association was found between EUM measurements during the third stage and parity, maternal age, fetal weight, duration of labor, gestational age, gravity or BMI. The rate of oxytocin use during the second stage and EUM measurements during the second or third stage did not differ among women with short versus long duration of the third stage. CONCLUSION Uterine activity during the third stage is comparable and as intense as that occurring during the second stage. Third stage length cannot be predicted by contraction intensity during the second or third stage of labor.