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Rupture of the unscarred uterus

James F Smith, MD, MA
Joseph R Wax, MD
Section Editor
Charles J Lockwood, MD, MHCM
Deputy Editor
Vanessa A Barss, MD, FACOG


Rupture of the pregnant uterus, similar to rupture of any internal organ, can be life-threatening for the mother and fetus. Most ruptures occur in women who have had a previous transmyometrial surgical incision, typically for cesarean delivery. Rupture of the unscarred uterus is rare, but the incidence is increasing. It is associated with higher major maternal and neonatal morbidity than cases of rupture of the scarred uterus [1].

This topic will review issues related to rupture of the unscarred uterus. Rupture of the scarred uterus is discussed separately. (See "Uterine rupture after previous cesarean delivery".)


Rupture of the unscarred pregnant uterus is a rare event, estimated to occur in 1/5700 to 1/20,000 pregnancies [2-5]. In a study of uterine ruptures in The Netherlands, the incidence of rupture in unscarred and scarred uteri was 0.7 and 5.1 per 10,000 deliveries, respectively; ruptures of unscarred uteri accounted for 13 percent of all ruptures [5]. A study from the United States reported rupture of the unscarred uterus in 4.54 per 100,000 deliveries, or about 1 in 22,000 deliveries [1]. The incidence of rupture in both scarred and unscarred uteri has increased in recent decades [6].

Rupture of the unscarred uterus occurs more frequently in resource-limited countries where prompt access to cesarean and instrument-assisted vaginal delivery is not widely available for management of obstructed labor [7-10]. Higher parity and frequency of contracted pelvises may also play a role.


Rupture of an unscarred uterus may be caused by trauma or congenital or acquired weakness of the myometrium. Sources of trauma include motor vehicle accidents and obstetric maneuvers (eg, internal or external version). The myometrium may be inherently weak because of a congenital disorder, such as Ehlers-Danlos type IV [11-14], or it may become weakened from protracted labor or use of strong uterotonic drugs (eg, misoprostol), which place prolonged stress on the myometrium [15,16]. Overdistension of the uterine cavity, whether absolute or relative to the size of the cavity, may be the major physical factor provoking rupture when the myometrium is weakened for any reason.

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Literature review current through: Nov 2017. | This topic last updated: Sep 26, 2017.
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