Sonographic assessment of the lower uterine segment during active labor in women with or without a uterine scar - a prospective study.

OBJECTIVES

No study thus far has evaluated the LUS thickness in active labor. In this study, we endeavored to assess the LUS during active labor.

METHODS

Using transabdominal sonography in the mid-sagittal position with a full urinary bladder, the thickness of the LUS was measured during active labor phase in women with or without a history of a previous cesarean section.

RESULTS

A total of 28 women with a previous cesarean delivery were compared to 29 women without a history of uterine surgery. The median LUS was significantly thinner in women with a uterine scar both during (4 versus 5 mm, p = .001) and between contractions (5 versus 7 mm, p = .011). Paired comparison of LUS thickness between and during contractions within each group showed that thinning of LUS during contraction was significant for both the previous CS group (p < .001) and the control group (p < .001). We found no correlation between LUS thickness and chances of successful TOLAC.

CONCLUSIONS

In this study, we characterized for the first time the LUS during active labor. We found that LUS was significantly thinner in women after a previous CS and that the LUS was significantly thinner during contraction.