Hypertonic uterine contraction o Localized abnormalities of uterine action constriction ring pathological retraction ring localized rings or constrictions of the uterus develop in led labol result of obstructed labor with marked streching and thinning of the lower uterine segment. The ring may be seen clearly as an abdominal indentationand signifies impending rupture of the lower uterine segmentHypertonic uterine contraction Localized abnormalities of uterine action ◼ constriction ring ◼ pathological retraction ring  localized rings or constrictions of the uterus develop in association with prolonged labors, which is often the result of obstructed labor, with marked streching and thinning of the lower uterine segment. The ring may be seen clearly as an abdominal indentationand signifies impending rupture of the lower uterine segment