Rupture of the uterus during pregnancy or labor is a serious emergency that can be fatal to both mother and fetus. Uterine rupture results in:
- rupture of the amniotic sac (bag of waters);
- partial or full delivery of the fetus into the abdominal cavity; and
- loss of oxygen delivery to the fetus.
Classic symptoms of rupture include:
- pain above and beyond normal labor pain;
- discontinuation of uterine contractions;
- signs of fetal heart rate abnormalities;
- hemorrhage; and
While uterine rupture is uncommon, it is most likely to occur during labor in a patient who has had a certain type of previous cesarean section?the cesarean section scar in the uterus tears open. If severe, the fetus may pass into the mother's abdomen. Other causes of uterine rupture include:
- history of surgery to remove uterine fibroids or other uterine surgery;
- trauma to the abdomen; and
- performance of external cephalic version (manipulation to reposition the fetus from a breech or transverse presentation to a cephalic-head-first-presentation); though, this is quite unusual.
Uterine rupture is a rare event, occurring in less than 1% of women with a low transverse cesarean section scar. For patients who have had a low vertical scar the rate of occurrence is approximately 2 to 4%. Women who have had a previous classical cesarean incision (an incision that is up and down across the whole uterus) have a significantly higher risk of rupture during subsequent pregnancies, approximately 4 to 8%, and are therefore advised to deliver any future pregnancies by cesarean section. Of note, the type of scar that is seen on the mother's abdomen does not necessarily reflect the type of scar that was made on the uterus. For this reason, obtaining operative records from a previous cesarean section is very important.
Dehiscence is the bursting open of a suture line. It is important to distinguish between uterine rupture and dehiscence. Dehiscence in pregnancy refers to separation of a uterine scar without the fetal membranes rupturing and without the fetus slipping into the abdominal cavity. Dehiscence occurs more commonly than actual rupture; bleeding can be minimal or absent. These scars can be separated for some time during the latter part of pregnancy and may not cause any difficulty during labor. A dehiscence is sometimes noted upon manual inspection of the uterine cavity after removal of the placenta. In a small percentage of cases, however, dehiscence may suddenly lead to rupture.