A tear in the uterus is a serious condition that can lead to numerous complications, including urologic injury, amniotic-fluid embolism (AFE), the need for a blood transfusion, hysterectomy, maternal death, and perinatal problems including neurological impairment or death of the baby. Causes of uterine rupture include multiple pregnancy (with twins, triplets, etc.), numerous previous pregnancies, labor with an unusually large baby, trauma, vaginal birth after cesarean section (VBAC), and the use of drugs intended to induce birth or an abortion, which is what this article elaborates on.
There are several drugs that can increase the risk of a uterine rupture in certain circumstances. The more notable ones are prostaglandins, including misoprostol (Cytotec), and oxytocin (Pitocin, Syntocinon). Epidural anesthetics may not increase the risk of uterine rupture in-and-of themselves, but they may do so indirectly by increasing the risk of oxytocin augmentation.
Prostaglandins are a group of drugs, such as dinoprostone (Cervidil, Prepidil, Prostin E2, Propess), which are derived from fatty acids originally found in prostate glands, although they are present in nearly all tissues and organs. They serve many functions, depending on their type and the cell receptors they chemically bind to. They are used as vasodilators (to relax the smooth muscle in blood vessels, causing them to dilate), bronchodilators (to dilate airways in the lungs by relaxing surrounding muscles), bronchoconstictors, or to constrict the uterus, among many other applications.
Some prostaglandins can be used to induce labor or abortion by “ripening” the cervix, a process in which cervical smooth muscle is relaxed, allowing for dilation, and myometrial muscle (the middle layer of the uterine wall) contracts. The increased risk of uterine hyperstimulation, however, also increases the possibility of changes in the fetal heart rate (FHR). There is also an increased risk of uterine rupture in VBACs.
Actually a synthetic prostaglandin, this drug is commonly used for cervical ripening despite it not having been approved for this use by the US Food and Drug Administration (FDA). In fact, an FDA alert issued in May 2005 warns, “there can be serious side effects, including a torn uterus (womb)”. Additional risks include hyperstimulation syndrome (more than five contractions in ten minutes or contractions lasting longer than 90 seconds), tachysystole (six or more contractions in 10 minutes for two consecutive ten-minute periods), and hypersystole (a single uterine contraction lasting longer than two minutes).
Oxytocin is a mammalian hormone made in the brain that also acts as a neurotransmitter. It stimulates contraction of the uterus during childbirth and secretion of breast milk during nursing. But unlike oxytocin, which is naturally secreted in bursts, synthetic forms of the hormone such as Pitocin are introduced into the body intravenously in a steady flow. The resulting contractions differ from natural contractions both in strength and effect.
With both natural and induced contractions, blood flow to the uterus decreases. But during the longer induced contractions, which are also closer together, blood flow may decrease even further, reducing oxygen to the baby. Other potential detriments to inducing labor with oxytocins include a greater likelihood in the need for pain medications such as epidurals, which are discussed below. But among the more serious hazards the more vigorous contractions Pitocin and Syntocinon can present are a premature separation of the placenta, laceration of the cervix, postbirth hemorrhage and, of course, rupture of the uterus.
The safety of anesthetic (decrease in sensation) and analgesic (decrease in pain) epidurals is a controversial topic. Epidurals are arguably safer than narcotics in that they do not comparatively slow labor or increase the risk of a cesarean. But compared to natural birth, the use of epidurals does pose certain risks.
With regard to the risk of uterine rupture, several studies have shown that analgesic epidurals increase the incidence of oxytocin augmentation. And while there is not much evidence that epidurals mask the signs of uterine rupture, it may be advisable for the obstetrician to insert an intrauterine pressure catheter when the expectant mother receives an epidural, especially if she is also receiving Pitocin and/or attempting a VBAC.
Signs of Uterine Rupture
A searing suprapubic pain is NOT the most common sign of uterine rupture during labor. Not only have studies shown that most uterine ruptures were revealed by abnormal FHR patterns, such patterns are the earliest and most common indication of a uterine rupture. The most commonly seen patterns are repetitive, deep variable decelerations and prolonged decelerations. FHR changes in a home VBAC should be interpreted with caution and quick transport to the hospital should be considered.
Other signs and symptoms of uterine rupture include:
- Intrapartum vaginal bleeding
- Postpartum hemorrhage
- Maternal instability in pulse and blood pressure
- Changes in maternal mental status (stupor, confusion, etc.)
- Maternal shock
- Fluid in the mother’s abdomen beyond the margins of her uterus
- Loss of fetal station
- Unusual pain in the region of the uterine incision (VBAC)
In most cases, an emergency exploratory laparotomy or coeliotomy (Ex-Lap), in which an incision through the abdominal wall allows access to the abdominal cavity, a cesarean delivery, and fluid and blood transfusions are indicated for the management of a uterine rupture. If the uterus cannot be repaired, or if the condition of the patient does not warrant it, a cesarean hysterectomy (removal of the uterus) may be necessary.