ABSTRACT
During labor, the uterus is transformed into two distinct segment. The active upper segment which becomes thick and the relatively passive lower segment which becomes thin with the progress of labor. The ratio between both segments used to indicate the progress of labor and imminent delivery. The safety of vaginal delivery depends mainly on the thickness of the lower uterine segment especially in patients with previous uterine scare or high risk pregnancy. Evaluation of progress of labor by measurement of the uterine wall thickness sonographyically to identify the safety of vaginal delivery in the our aim. 43 full term pregnant women early in labor mean age 24.93, DS 4.03 years, 10 primigravida and 33 multigravida [Parity < 3] vertex presention, with no risk factors or uterine scar. Repeted measurement of upper and lower uterine segments thickness sonographically were done in relation to cervical dilation which also measured. The result shows a statistically significant progressive increase in upper uterine segment wall thickness in relation to cervical dilatation and the lower uterine segment shows progressive thinning, the ratio was 1.05 in late pregnancy, 1.37 at the beginning of active phase of labor and 9.03 at full cervical dilator. We conclude that labor is imminent when the mean lower uterine segment thickness was < 0.35 cm and mean upper uterine segment thickness > 3.0 cm this should be considered in high risk pregnancies when digital examination carries the risk of ascending infection in cases of PROM or ante partum hemorrhage