Rupture of the uterus is one of the most feared complications of pregnancy. You may have heard of uterine rupture in discussions of major childbirth complications, particularly in the context of vaginal birth after caesarean, or VBAC.

What is uterine rupture?

The term "uterine rupture" is used for anything in a continuum of events, from a weak spot in the uterine wall noticed by the surgeon at the time of caesarean to the catastrophe of the uterus tearing open and the fetus, placenta, and a lot of blood extruding into the mother's abdomen usually with the loss of the baby and the mother's life is in jeapordy.

Who is at risk for uterine rupture?

Women who have had previous surgery on the uterus, particularly on the upper muscular portion (caesareans that werenot low transverse) are at increased risk for uterine rupture. Previous classical caesareans, where the incision is near the top of the uterus, prior removal of fibroid tumors if the incision extended through the full thickness of the uterine wall, any other uterine surgery that went through the full depth of the muscular portion of the uterus, ormultiple (three or more) prior low transverse caesareans all put a pregnant woman at increased risk. Even without prior surgery, having had more than five full-term pregnancies, having an overdistended uterus (as with twins or other multiples), abnormal positions of the baby such as transverse lie, and the use of oxytocin and prostaglandins may increase the risk. There is no evidence that DandC, first-trimester abortion, removal of superficial fibroids, or pelvic surgery that did not involve the uterus increase the risk.

What is the risk?

Most uterine ruptures occur without symptoms and do not cause problems for the mother or fetus. This mild type is only noticed when surgery is required for other reasons. In the most severe form of uterine rupture, where the tear is large or it cuts across the uterine blood vessels, the mother may haemorrhage and require a blood transfusion, the uterus may not be repairable and must be surgically removed (hysterectomy), the baby may not survive the lack of oxygen, and (rarely) the mother's life, too, cannot be saved. The majority of women who have had a severe uterine rupture will be advised not to get pregnant again, due to the risk of repeated rupture.

The uterus can rupture before or during labour. In a large study of mothers who had one previous low transverse caesarean, the risk of uterine rupture was 1 per 625 women who chose repeat caesarean without labour, 1 per 192 women who went into labour and tried for VBAC, 1 per 129 for those who had their labour induced without prostaglandins (usually with oxytocin), and 1 per 41 when prostaglandin medications were used for induction. When the uterus did rupture, 1 in 18 babies died, and 1 in 23 of the women required a hysterectomy.

To put these sobering numbers in some perspective, assuming the risk of losing the baby is the same in these different situations, of the women who tried for VBAC and didn't use prostaglandins, 1 baby in 3,500 labours would be lost, instead of 1 in 11,000 elective repeat caesareans. While this is a four-fold increase in the risk, the actual chances are small, and may be outweighed by other risks of surgery to the mother and her babies.

Signs of uterine rupture

In most cases, significant uterine rupture is signaled by severe, localized pain and abnormalities of the fetal heart rate. There may be vaginal bleeding, and the vaginal examination may show that the baby is not as low in the birth canal as he had been earlier. When uterine rupture is diagnosed during labour, an emergency caesarean is performed. Usually the baby's life can be saved. When uterine rupture occurs outside a hospital setting, it is more likely to lead to disastrous consequences, even if the mother is transported quickly to the emergency room for stabilization and emergency surgery.