Study of the third stage of labor by color Doppler sonography.

We wanted to evaluate whether improvement in ultrasound equipment in the last 5 years altered our perception of the phases of placental separation during the third stage of labor. We also investigated the influence of active management on the third stage of labor after sonographically verified placental separation. Between January and November 2001, the third stage of labor was examined in 55 women at 37-41 weeks of gestation by color Doppler sonography. The duration of blood flow between the myometrium and the placenta, the latent phase, the detachment phase, and the expulsion phase were measured and compared with the corresponding values of an earlier cohort of 57 patients investigated between November 1994 and August 1995. In the later cohort, both the duration of maternal blood flow and the detachment phase were significantly longer than in the earlier cohort (33 s +/- 48 s vs 0 s, P<0.0001 and 56 s+/-45 s vs 37 s+/-21 s, P<0.01, respectively), whereas the latent phase was significantly shorter (101 s+/-87 s vs 213 s+/-180 s, P<0.0001). There was no statistically significant difference in the length of the expulsion phase or the third stage of labor. The later cohort showed a statistically significantly more frequent multiphasic placental detachment ( P<0.05). Improvement in ultrasound equipment resulted in an earlier detection of the onset of placental separation, leading to a shorter latent phase and consecutively increased duration of the detachment phase, whereas the total duration of the third stage of labor remained unchanged. Furthermore, increased sensitivity of Doppler sonography led to a longer visualization of blood flow between the myometrium and the placenta in the normal third stage of labor.