Uterine atony is the failure of the uterus to contract adequately following delivery. Contraction of the uterine muscles during labor compresses the blood vessels and slows flow, which helps prevent hemorrhage and facilitates coagulation. Therefore, a lack of uterine
muscle
Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...
contraction can lead to an acute
hemorrhage
Bleeding, hemorrhage, haemorrhage or blood loss, is blood escaping from the circulatory system from damaged blood vessels. Bleeding can occur internally, or externally either through a natural opening such as the mouth, nose, ear, urethra, vag ...
, as the vasculature is not being sufficiently compressed.
[ Text was copied from this source, which is available under ]
Creative Commons Attribution 4.0 International License
Uterine atony is the most common cause of
postpartum hemorrhage
Postpartum bleeding or postpartum hemorrhage (PPH) is often defined as the loss of more than 500 ml or 1,000 ml of blood following childbirth. Some have added the requirement that there also be signs or symptoms of low blood volume for ...
, which is an emergency and potential cause of fatality. Across the globe, postpartum hemorrhage is among the top five causes of maternal death.
Recognition of the warning signs of uterine atony in the setting of extensive postpartum bleeding should initiate interventions aimed at regaining stable uterine contraction.
Risk factors
There are many risk factors for uterine atony and several are due to the type of labor a mother experiences such as prolonged labor, labor lasting less than 3 hours, uterine inversion, the use of magnesium sulfate infusions, and extended use of oxytocin. Uterine distention caused by things like more than one fetus present,
polyhydramnios
Polyhydramnios is a medical condition describing an excess of amniotic fluid in the amniotic sac. It is seen in about 1% of pregnancies. It is typically diagnosed when the amniotic fluid index (AFI) is greater than 24 cm.
There are two clin ...
,
fetal macrosomia
Large for gestational age (LGA) is a term used to describe infants that are born with an abnormally high weight, specifically in the 90th percentile or above, compared to other babies of the same developmental age. Macrosomia is a similar term tha ...
,
uterine fibroid
Uterine fibroids, also known as uterine leiomyomas or fibroids, are benign smooth muscle tumors of the uterus. Most women with fibroids have no symptoms while others may have painful or heavy periods. If large enough, they may push on the bl ...
s,
chorioamnionitis
Chorioamnionitis, also known as intra-amniotic infection (IAI), is inflammation of the fetal membranes ( amnion and chorion), usually due to bacterial infection. In 2015, a National Institute of Child Health and Human Development Workshop expert ...
can also lead to decreased uterine function and atony. Retained placental tissue or placental disorders, such as an adherent placenta,
placenta previa
Placenta praevia is when the placenta attaches inside the uterus but in a position near or over the cervical opening. Symptoms include vaginal bleeding in the second half of pregnancy. The bleeding is bright red and tends not to be associated wi ...
, and
abruption placentae increase the mother's risk of PPH. Body mass index (BMI) above 40 and
coagulopathies are known risk factors.
Magnesium sulfate
Magnesium sulfate or magnesium sulphate (in English-speaking countries other than the US) is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, ...
is used often in patients with
preeclampsia
Pre-eclampsia is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. When it arises, the condition begins after 20 weeks of pregnancy. In severe cases of the disease ...
and
eclampsia
Eclampsia is the onset of seizures (convulsions) in a woman with pre-eclampsia. Pre-eclampsia is one of the hypertensive disorders of pregnancy that presents with three main features: new onset of high blood pressure, large amounts of protein in ...
, can inadvertently inhibit uterine contractions. In addition, preeclampsia can lead to blood disorders such as
thrombocytopenia
Thrombocytopenia is a condition characterized by abnormally low levels of platelets, also known as thrombocytes, in the blood. It is the most common coagulation disorder among intensive care patients and is seen in a fifth of medical patients an ...
, platelet abnormalities, and
disseminated intravascular coagulation
Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
. Cesarean delivery, especially after prolonged labor, may cause the muscles of the uterus to become tired and stop contracting or contraction can be inhibited at the surgical site.
Epidemiology
Uterine atony occurs during 1 in 40 births in the United States and is responsible for at least 80% of cases of postpartum hemorrhage.
Pathophysiology
The uterus is composed of an interconnected muscle fibers known as the
myometrium
The myometrium is the middle layer of the uterine wall, consisting mainly of uterine smooth muscle cells (also called uterine myocytes) but also of supporting stromal and vascular tissue. Its main function is to induce uterine contractions.
Struc ...
. The blood vessels that provide the blood supply to the placenta pass through this muscle.
After labor it is the contraction of these muscles that physically squeeze the blood vessels so that
hemostasis
In biology, hemostasis or haemostasis is a process to prevent and stop bleeding, meaning to keep blood within a damaged blood vessel (the opposite of hemostasis is hemorrhage). It is the first stage of wound healing. This involves coagulation, whi ...
can occur after the delivery of the fetus and the placenta.
Local hemostatic factors like
tissue factor type-1 plasminogen activator inhibitor and platelets and clotting factors aid in stopping the blood flow.
This physiological contraction does not occur if the myometrium becomes atonic.
Oxytocin
Oxytocin (Oxt or OT) is a peptide hormone and neuropeptide normally produced in the hypothalamus and released by the posterior pituitary. It plays a role in social bonding, reproduction, childbirth, and the period after childbirth. Oxytocin ...
is released continuously during labor to stimulate uterine muscle contraction so the that the fetus can be delivered and it is continued to be released after delivery to stop blood flow.
If the oxytocin receptors become desensitized and no longer respond to the hormone then the uterus does not contract.
The uterus can also be structurally damaged or distended to prevent contraction. Therefore, as placenta is delivered
arteries
An artery (plural arteries) () is a blood vessel in humans and most animals that takes blood away from the heart to one or more parts of the body (tissues, lungs, brain etc.). Most arteries carry oxygenated blood; the two exceptions are the pu ...
are damaged and without the muscle contractions hemostasis cannot be reached.
Blood loss is an expected part of labor and less than 500 mL is considered normal. Generally, primary PPH is classified as being more than 500 mL of blood lost in the first 24 hours following delivery.
Those who have a caesarean section typically have more blood loss than a vaginal birth; so 1000 mL is commonly used to determine excessive blood loss. It is easy to underestimate maternal blood loss because the primary method of assessment is visual observation.
Evaluation and diagnosis
Identifying risk factors early in the pregnancy is essential in managing uterine atony and PPH. This allows for planning and organizing the necessary resources including staff, medicines, assistive devices, and the proper blood products. The delivery plan should also be cognizant of the ability of the hospital or facility to provide an appropriate level of care if any complications occur.
Most diagnosis of uterine atony are made during the physical exam directly upon completion of the delivery. Diffuse uterine atony is typically diagnosed by patient observation rather than blood loss. The uterus can be directly palpated or observed indirectly using a
bimanual examination post delivery. An atonic uterus can feel soft, "boggy" and/or enlarged.
Bleeding from the
cervical os
The cervical canal is the spindle-shaped, flattened canal of the cervix, the neck of the uterus.
Anatomy
The cervical canal communicates with the uterine cavity via the internal orifice of the uterus (or internal os) and with the vagina via the ...
is also common. If the atony is localized to one area of the uterus, the
upper, fundal region may be still be squeezing while the lower uterine segment is non functional. This can be difficult to see with a cursory abdominal examination and easily overlooked. Therefore, a comprehensive vaginal, abdominal, and rectal examination should be performed. The physical examination may include
ultrasound
Ultrasound is sound waves with frequency, frequencies higher than the upper audible limit of human hearing range, hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hea ...
imaging for rapid visualization of the uterus and other causes of bleeding.
Expulsion of gestational products such as the
placenta
The placenta is a temporary embryonic and later fetal organ that begins developing from the blastocyst shortly after implantation. It plays critical roles in facilitating nutrient, gas and waste exchange between the physically separate mater ...
and rapid identification of obstetric lacerations, helps exclude other causes of PPH.
Laboratory tests can be drawn if coagulopathies are suspected.
Treatment and management
Prevention
Before delivery all patients should be screened for risk factors and then assigned a postpartum hemorrhage risk stratification based on the
American College of Obstetricians and Gynecologists
The American College of Obstetricians and Gynecologists (ACOG) is a professional association of physicians specializing in obstetrics and gynecology in the United States. Several Latin American countries are also represented within Districts of ...
recommendations. If the woman is at a medium risk, blood should be
typed and screened. Those assessed to be high risk should be
typed and cross-matched.
Active management of the
third stage of labor is routinely implemented and is considered the standard for patient care. It can be utilized to reduce the risk of PPH. Active management of the third stage includes uterine massage and a IV low dose oxytocin. Whether it is given just before or after the delivery of the placenta is subject to provider preference.
It is suggested that using an
uterotonic
A uterotonic, also known as ecbolic, are pharmacological agents used to induce contraction or greater tonicity of the uterus. Uterotonics are used both to induce labor and to reduce postpartum hemorrhage.
Labor induction in the third trimester of ...
, such as oxytocin, prophylactically will help reduce blood loss and the need for a blood transfusion after delivery.
A uterine massage is performed by placing a hand on the lower abdomen and using repetitive massaging or squeezing movements in attempt to stimulate the uterus. It is theorized, the massaging motion stimulates uterine contraction and may also trigger the release of local
prostaglandin
The prostaglandins (PG) are a group of physiologically active lipid compounds called eicosanoids having diverse hormone-like effects in animals. Prostaglandins have been found in almost every tissue in humans and other animals. They are derive ...
s to help hemostasis.
Treatment
If uterine atony occurs even after all preventative measures have been taken, medical management should be implemented. Uterine
fundal massage
Fundal massage, also called uterine massage, is a technique used to reduce bleeding and cramping of the uterus after childbirth or after an abortion. As the uterus returns to its nonpregnant size, its muscles contract strongly, which can cause pai ...
and compression should be maintained, while drugs are administered.
An intravenous catheter should also be started to administer fluids, medications, and blood products
There are several different types of uterotonic drugs that may be given, and the each has its own advantages and disadvantages. Moreover, the use of combination uterotonic therapy is a common practice and might be more effective at controlling bleeding than monotherapy. Some combinations might include oxytocin plus misoprostol, oxytocin plus ergometrine, and carbetocin.
Medications used for PPH include the following:
# Oxytocin (
Pitocin
Synthetic oxytocin, sold under the brand name Pitocin among others, is a medication made from the peptide '' oxytocin''. As a medication, it is used to cause contraction of the uterus to start labor, increase the speed of labor, and to stop ...
) Stimulation of oxytocin receptors in the uterine muscle leads to contractions. The number of these receptors increases during pregnancy and with labor. There are also more in the fundus than in the lower uterine segment. Oxytocin has a quick onset of action, within a few minutes, but also loses effectiveness quickly because of a short half-life. The medicine is given in a rapid infusion and may cause hypotension. Oxytocin alone is the usually treatment of atony in the US. However, if bleeding is uncontrolled after administration of oxytocin, then a second uterotonic is given.
#
Carbetocin
Carbetocin, sold under the brand names Pabal among others, is a medication used to prevent excessive bleeding after childbirth, particularly following Cesarean section. It appears to work as well as oxytocin. Due to it being less economical than ...
: A synthetic analog of oxytocin, works similarly to oxytocin but the half-life is much longer. It binds to smooth muscle receptors of the uterus, like oxytocin and has been reported to produce a stable uterine contraction, followed by rhythmic contractions. It is not available in the US but is available in many countries for the prevention of uterine atony and hemorrhage.
#
Methylergonovine
Methylergometrine, also known as methylergonovine and sold under the brand name Methergine, is a medication of the ergoline and lysergamide groups which is used as an oxytocic in obstetrics and in the treatment of migraine. It reportedly produces ...
: This is an ergot alkaloid and has multiple mechanisms of action to induce fast, regular uterine contractions which leads to sustained uterine contraction. It can cause peripheral vasoconstriction and is contraindicated in patients with hypertension or pregnancy related hypertension.
# 15-methyl-PGF2-alpha (
Hemabate
Carboprost ( INN, trade names for the tromethamine salts Hemabate, Tham) is a synthetic prostaglandin analogue of PGF2α (specifically, it is 15-methyl-PGF2α) with oxytocic properties.
Carboprost's main use is in the obstetrical emergency of p ...
,
Carboprost
Carboprost (INN, trade names for the tromethamine salts Hemabate, Tham) is a synthetic prostaglandin analogue of PGF2α (specifically, it is 15-methyl-PGF2α) with oxytocic properties.
Carboprost's main use is in the obstetrical emergency of po ...
) Highly effective but it is expensive. It can cause bronchospasm and it should be avoided in asthmatics. May cause diarrhea, fevers, or tachycardia.
#
Misoprostol
Misoprostol is a synthetic prostaglandin medication used to prevent and treat stomach and duodenal ulcers, induce labor, cause an abortion, and treat postpartum bleeding due to poor contraction of the uterus. Misoprostol is taken by mouth wh ...
(Cytotec): A synthetic
prostaglandin E1 analog oral medication that can stimulate uterine contractions. Misoprostol does not need to be refrigerated because it is heat stable. It is easy to administer compared with oxytocin and ergot alkaloids in low-resource areas where refrigeration and sterile needles are not available. May cause a low-grade fever.
#
Dinoprostone
Prostaglandin E2 (PGE2), also known as dinoprostone, is a naturally occurring prostaglandin with oxytocic properties that is used as a medication. Dinoprostone is used in labor induction, bleeding after delivery, termination of pregnancy, and ...
(Prostin E2): An alternative prostaglandin to misoprostol.
After the medication is administered, the mother should be closely observed for to confirm the bleeding has stopped. If the bleeding has not stopped or physical exam does not show signs of restored uterine function within 30 minutes of medication administration, immediate invasive interventions are recommended.
Tamponade
Tamponade () is the closure or blockage (as of a wound or body cavity) by or as if by a tampon, especially to stop bleeding.
Tamponade is a useful method of stopping a hemorrhage. This can be achieved by applying an absorbent dressing directl ...
techniques include uterine packing (extending into the vagina) with gauze that also has a Foley catheter in place to allow for bladder drainage. It is inexpensive and readily available.
Balloon tamponade is the suggested method of tamponade in guidelines for management of PPH. A
bakri balloon
The Bakri Balloon is a medical device invented and designed by Dr. Younes Bakri in 1999.
The obstetrical balloon is a 24 French, 54 cm-long, silicone catheter with a filling capacity of 500 mL. The device is used for the temporary control a ...
to tamponade (also with vaginal packing) can be used with Foley catheter insertion to facilitate bladder drainage.
Vacuum-induced uterine tamponade is newer technique that uses low-level vacuum to evacuate blood from the uterine cavity and facilitate uterine contraction
Surgical management techniques include:
* Compression sutures such as the
B-Lynch
*
Uterine curettage to remove retained placental products
* Uterine artery ligation, with or without ligation of the tubo-ovarian vessels.
Ligation of the uterine and utero-ovarian arteries can decrease uterine bleeding by reducing the pressure of arterial blood flow in the uterus. It will not completely control the bleeding but may decrease blood loss while other interventions are being attempted.
*
Hypogastric artery
The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis.
Structure
The internal iliac artery supplies the walls and viscera of the pelvis, the buttock, the reproductive organs, and the medial compart ...
ligation. Bilateral ligation of the internal iliac arteries reduces the pulse pressure of blood flowing to the uterus similar to uterine artery ligation. However, it is not a common procedure because of the degree of difficulty and risks.
*
Hysterectomy
Hysterectomy is the surgical removal of the uterus. It may also involve removal of the cervix, ovaries (oophorectomy), Fallopian tubes (salpingectomy), and other surrounding structures.
Usually performed by a gynecologist, a hysterectomy may b ...
Complications
PPH can cause a multitude of complications including:
* death
*
hypovolemic shock
Hypovolemic shock is a form of shock caused by severe hypovolemia (insufficient blood volume or extracellular fluid in the body). It could be the result of severe dehydration through a variety of mechanisms or blood loss. Hypovolemic shock is a ...
*
disseminated intravascular coagulopathy
Disseminated intravascular coagulation (DIC) is a condition in which blood clots form throughout the body, blocking small blood vessels. Symptoms may include chest pain, shortness of breath, leg pain, problems speaking, or problems moving parts o ...
* renal failure
* hepatic failure
*
adult respiratory distress syndrome
Acute respiratory distress syndrome (ARDS) is a type of respiratory failure characterized by rapid onset of widespread inflammation in the lungs. Symptoms include shortness of breath (dyspnea), rapid breathing (tachypnea), and bluish skin color ...
In low‐income countries there are several other factors that play a role in PPH risk. Poor nutritional status, lack of healthcare access, and limited blood product supply are additional factors that increase morbidity and mortality.
Postpartum anemia is common after an episode of uterine atony and postpartum hemorrhage.
Severe anemia due to PPH may require red cell transfusions, depending on the severity of anemia and the degree of symptomatology attributable to anemia. A common practice is to offer a transfusion to symptomatic women with a hemoglobin value less than 7 g/dL. In most cases of uterine atony-related postpartum hemorrhage, the amount of iron lost is not fully replaced by the transfused blood. Oral iron should thus be also considered. Parenteral iron therapy is an option as it accelerated recovery. Most women with mild to moderate anemia, however, resolve the anemia sufficiently rapidly with oral iron alone and do not need parenteral iron.
Prognosis
Women with a history of PPH have a 2 to 3 times higher risk of PPH in their following pregnancies.
References
External links
{{Pathology of pregnancy, childbirth and the puerperium
Health issues in pregnancy