Your uterus nourishes your growing baby for nine months. Once your baby is born, many of the blood vessels in your uterus break. The muscles of your uterus contract and squeeze them shut.
Uterine atony occurs when the muscles don't contract, allowing bleeding to continue. This is a medical emergency. Uterine atony can be fatal.
What Is Uterine Atony?
During pregnancy, your growing baby gets oxygen and nutrition from the blood vessels of your uterus. Spiral arteries, which develop during pregnancy, provide blood to your baby.
After the baby's born, these spiral arteries are left broken. The muscles of your uterus — called the myometrium — contract and squeeze them shut. If they don't, uterine atony may occur, causing enormous blood loss.
Uterine atony is a known complication of both vaginal birth and cesarean section. It can occur after miscarriages and medical abortions, too.
What Causes Uterine Atony?
Soon after delivery, your pituitary gland releases oxytocin. This hormone stimulates uterine muscle contractions and stops the bleeding.
The basic cause of uterine atony is that the muscles of the uterus don't contract.
What Are the Risk Factors for Uterine Atony?
Certain factors put you at high risk for developing uterine atony. They include:
- A prolonged and difficult labor
- Excessive stretching of the uterus, which happens if you deliver a very large baby, multiple babies, or have excessive water collection (polyhydramnios)
- Using oxytocin to induce labor for a prolonged period
- Using drugs like magnesium sulfate
- The presence of fibroids, or benign growths in the uterus
- Having chorioamnionitis, or an infection of the membranes covering the baby
- Obesity
What Are the Symptoms of Uterine Atony?
The most significant symptom of uterine atony is prolonged bleeding from the uterus. This may cause you to lose a dangerous amount of blood.
Some bleeding after childbirth is expected. But if you feel you're bleeding heavily or having to change pads frequently, you should alert your doctor. Losing a lot of blood can cause:
- Low blood pressure (hypotension)
- Fast heartbeat
- Pale appearance
- Reduced urination
- Dizziness
- Unconsciousness
How Is Uterine Atony Diagnosed?
Your doctor diagnoses uterine atony by the feel and size of your uterus. If you have delivered a baby by cesarean section, your doctor will feel your uterus after closing the incision. If you deliver vaginally, your doctor will feel your uterus by vaginal examination.
Usually, the uterus contracts and shrinks soon after a baby is born. If you have uterine atony, the uterus remains large and feels soft.
Sometimes, the atony affects only the lower part of the uterus. The upper part — or fundus — may feel normal. While your doctor will feel for the softness typical of uterine atony around your entire uterus, they may focus on this lower area if the fundus feels normal.
About three-quarters of postpartum hemorrhage — or heavy bleeding after childbirth — is caused by uterine atony. To be sure, your doctor may also examine you for:
- Tears of the cervix, vagina, or uterus
- Incomplete delivery of the placenta, which may also cause heavy bleeding
What Is the Treatment for Uterine Atony?
Uterine atony needs urgent treatment. Once the blood loss is stopped, you may need one or more blood transfusions to recuperate. Your doctor may also give you intravenous infusions, oxygen, and other drug treatments if your blood pressure is low. This can include:
- Oxytocin (Pitocin). Usually given slowly in an intravenous infusion, oxytocin stimulates the uterine muscles so they'll contract. This squeezes the uterine spiral arteries and stops the bleeding.
- Methylergonovine (Methergine). This drug can reverse the atony and stop blood loss. Your doctor won't use it, though, if you have hypertension (high blood pressure).
- 15-methyl-PGF2, misoprostol, and dinoprostone. These are prostaglandins, or chemicals that have biological actions. They're given as injections or as vaginal or rectal suppositories.
- Surgery. If you're losing blood even after medical treatment, your doctor may use surgical methods, including:
●Uterine packing with gauze. This method tries to stop the bleeding of uterine atony by applying direct pressure on the bleeding arteries.
●Uterine balloons. Special balloons are placed into your uterus and inflated with air or saline solution. This method also relies on direct pressure.
●Uterine artery ligation. Your doctor ties off the artery that carries blood to the uterus. This will stop the blood loss. Your doctor may have to do this if other methods have failed.
Hysterectomy. If nothing else stops the bleeding, your doctor may have to remove your uterus to save your life. This major surgery is called a hysterectomy and is only done as a last resort. After a hysterectomy, you can't have babies again.
