What is Uterine Atony?
Uterine atony is a condition where the muscle cells in the main body of the uterus, called myometrial cells, don’t contract properly in response to a natural hormone called oxytocin that’s released during childbirth. When this happens, it can cause heavy bleeding after childbirth, known as postpartum hemorrhage.
Normally, after the placenta is delivered, broken blood vessels called spiral arteries need to contract to stop the bleeding. However, these blood vessels lack muscle tissue and rely on the contraction of the uterus to squeeze them and prevent bleeding. When the uterus doesn’t contract enough, as in uterine atony, these blood vessels can’t close properly, which leads to excessive bleeding.
Uterine atony is a leading cause of postpartum hemorrhage, which can quickly become a serious emergency in childbirth. Around the world, this condition is one of the top five reasons why mothers might die during childbirth.
What Causes Uterine Atony?
Uterine atony, a condition where the uterus does not contract properly after childbirth, can be caused by several factors. These include a long labor, very fast labor, an overly large uterus due to multiple babies, excessive amniotic fluid, or a very large baby. Additionally, having a uterus with non-cancerous growths (fibroids), an infection of the amniotic fluid and membranes surrounding the baby (chorioamnionitis), receiving magnesium sulfate infusions, or long-term use of a hormone called oxytocin can also lead to uterine atony.
Problems with the uterus contracting, either in one specific area or throughout the entire uterus, can also happen due to a variety of reasons. One such reason is having parts of the placenta still in the uterus after childbirth. Other potential causes; disorders of the placenta itself such as when the placenta grows too deeply into the uterine wall (morbidly adherent placenta), when the placenta covers the cervix (placenta previa), or when the placenta detaches from the uterine wall too early (abruption placentae); disorders affecting the blood’s ability to clot properly (coagulopathy); and when the uterus turns inside out (uterine inversion).
It’s also worth noting that individuals with a body mass index (BMI) over 40, which falls into the category of severe obesity, also have a higher risk of uterine atony after childbirth.
Risk Factors and Frequency for Uterine Atony
In the United States, a problem arises in 1 out of 40 births when the uterus doesn’t contract properly after delivery. This issue is the reason for at least 75% of cases of heavy bleeding after giving birth, also known as postpartum hemorrhage.
Signs and Symptoms of Uterine Atony
When a woman is pregnant, it’s super important that health professionals keep an eye out for certain risk factors which might make it likely for her to experience heavy bleeding after childbirth. Detecting these risks in advance means doctors can be prepared and have the right resources available, like extra staff, necessary medications and equipment, IV access, and blood products. Doctors are especially cautious if a woman has certain conditions, such as a complicated placenta, a significantly high BMI before pregnancy, a serious bleeding disorder, or other serious health risks. In these cases, it’s advisable for the baby to be delivered in a center equipped to deal with these potential complications.
Once the baby is delivered, the doctors can tell if the woman is experiencing heavy post-birth bleeding by checking during the delivery itself, whether it’s a natural delivery or a c-section. They would typically feel for an unusually large and soft uterus– and investigate any excess bleeding. They’ll also quickly rule out if there are any leftover pregnancy tissue or trauma from childbirth. If things look suspicious, further tests might be performed, such as an ultrasound.
Testing for Uterine Atony
If your doctor suspects diffuse uterine atony, the diagnosis could be triggered by detecting more blood loss than usual. Uterine atony refers to a condition where the uterus, the womb where a baby grows, fails to contract properly after childbirth. During an examination, your doctor might find that your uterus is softer and larger than normal and may contain a significant amount of blood.
In the case of focal localized atony, the upper part of your uterus may be contracting well while the lower part is expanded and weakly contracting. This might be hard to detect during a regular stomach examination, but might become noticeable during a vaginal examination.
To confirm the condition, your doctor may perform a digital exploration of the uterine cavity – this means they might manually investigate your uterus. However, this can only be done if you have received adequate anesthesia to avoid discomfort or pain. An alternative is a bedside obstetric ultrasound imaging – a safe scan that uses sound waves to create an image of your uterus. And to rule out any cuts or tears, your doctor might perform a promptly executed examination with sufficient lighting.
Treatment Options for Uterine Atony
Before giving birth, it’s important for doctors to recognize if a woman is at medium or high risk for excessive bleeding, also known as postpartum hemorrhage (PPH). Factors for medium risk include previous uterine surgery, carrying multiple babies at once, having had many pregnancies, previous PPH, large noncancerous growths called fibroids, macrosomia (a very large baby), a body mass index over 40, anemia, chorioamnionitis (an infection of the uterus), a prolonged second stage of labor, use of the hormone oxytocin for more than 24 hours, and having been given magnesium sulfate. High-risk factors include placenta previa or accreta (conditions where the placenta is abnormally placed or attached), a bleeding disorder, or having two or more medium risk factors. A machine that collects and returns blood lost during surgery, known as a cell saver, may be considered for women at high risk of PPH, but it is not used routinely because of cost.
To prevent excessive bleeding during birth, healthcare providers follow what’s called the active management of the third stage of labor. This involves massaging the uterus and gently pulling on the umbilical cord while giving oxytocin, a hormone that can help the uterus contract and deliver the placenta.
If a woman’s uterus isn’t contracting well after childbirth, healthcare providers should be ready for initial medical treatment. This includes using medications to improve tone and induce uterine contractions, massaging the uterus and making sure the uterus is empty of all afterbirth, and giving intravenous (IV) fluids. A whole team of healthcare providers is on standby to help if needed. Medications to treat uterine atony (lack of muscle tone in the uterus) include oxytocin, methylergonovine, and several others.
If medications don’t work to control the bleeding, then surgical methods may be used. Doctors can place a tamponade, or blockage, using gauze or a balloon to stop the bleeding. Procedures can also be done, like uterine curettage (removal of the lining of the uterus) or uterine artery ligation (tying off the blood vessels to the uterus), among others. In severe cases, a hysterectomy (removal of the uterus) may be necessary.
What else can Uterine Atony be?
If a woman’s uterus turns inside out and extends into the vagina, a condition known as uterine eversion, it becomes more difficult to diagnose through the usual physical checks. This condition often happens after a vaginal childbirth and makes it harder to detect the usual signs of a softened and enlarged uterus. Instead, an abnormally colored mass might appear in the vagina. The standard procedure for this would be to immediately put the uterus back into its original position. After this, steps are taken to ensure that the uterus returns to its normal state, which will prevent the condition from happening again.
What to expect with Uterine Atony
Women who have previously had Postpartum Hemorrhage (PPH), which is heavy bleeding after giving birth, could face as much as a 15% risk of experiencing it again in a future pregnancy. It’s important to note that this risk is partially dependent on the underlying cause of the PPH. For example, women with class 3 obesity, which is regarded as severe obesity, could face a higher risk of experiencing PPH again.
Recovery from Uterine Atony
Postpartum anemia, a condition where the body lacks enough healthy red blood cells, is a common problem after a woman experiences uterine atony (a condition where the uterus loses muscle tone) and postpartum hemorrhage (excessive bleeding after childbirth). In severe cases, depending on the anemia’s seriousness and symptoms directly tied to anemia, a blood transfusion may be needed. Usually, transfusions are given to women having serious symptoms and a hemoglobin (a protein in red blood cells that carries oxygen) level less than 7 g/dL.
In many cases of postpartum hemorrhage due to uterine atony, the iron lost is not fully compensated by the transfused blood, so taking oral iron can also be a useful consideration. Iron injections can speed recovery and is an option; however, most women with mild-to-moderate anemia recover sufficiently quickly with oral iron alone, so injections aren’t typically necessary.
