Introduction

Uterine atony refers to a weak uterus that occurs as a result of inadequate contraction during and after childbirth. This means the muscles of the uterus do not contract enough to clamp the placental blood vessel shut after the baby is delivered.

It is a known complication of caesarean and vaginal delivery and can also occur after a miscarriage or medical abortion. It is important to understand uterine atony as it is a major cause of postpartum bleeding and one of the top five causes of maternal mortality. It is a life-threatening condition that requires immediate medical attention.

Understanding the uterus

The uterus (also known as a womb) is a vital reproductive organ. It undergoes many changes during pregnancy to nurture and house the growing foetus before birth. It also plays several key roles during pregnancy including growing with the foetus, implantation, supporting the placenta, protection from infection and childbirth.

Anatomically, the uterus is divided into three (3) parts; the upper (the fundus), the main (the body) and the lower (the cervix) part. The uterine wall is made of three (3) layers; the outer (perimetrium), middle (myometrium) and inner (endometrium) layer. The spinal arteries supply the endometrium with blood. During labour, regular, strong uterine muscle contractions cause the cervix to change in preparation for the baby to be delivered.

After delivery, the myometrium muscles continue to contract to stop bleeding from these arteries. These contractions reduce blood flow and in return increase the chances of blood clotting which can prevent heavy bleeding after childbirth.

What is uterine atony?

Uterine atony refers to the inadequate contraction of the uterine muscles in response to oxytocin released during labour. It is caused by the inability of the myometrium to contract and retract sufficiently in response to a hormone called oxytocin, following childbirth. Oxytocin is released before labour and during childbirth to stimulate the uterus to contract. Effective myometrial contractions are important to minimise bleeding. It is a major cause of postpartum haemorrhage (PPH), a life-threatening condition and an obstetric emergency.¹ It has been linked to 70 percent of cases and is the major cause of maternal morbidity and mortality.²

Several known risk factors may increase the chances of developing uterine atony, some include:

• prolonged labour
• primiparity (first time having a baby)
• multiple babies at birth (especially five or more)
• prolonged exposure or excessive use of labour-inducing medications like synthetic oxytocin
• use of drugs like general anaesthesia during childbirth
• a body mass index of 40 or above and
• history of previous postpartum haemorrhage

Other risk factors include:

• maternal age above 35
• an overdistended uterus
• larger than usual uterus

Uterine distention often occurs when a foetus is very large, when there are multiple foetuses or when an excess accumulation of amniotic fluid occurs. Existing pathological conditions may be additional risk factors for uterine atony.

For example, the presence of fibroids (non-cancerous growths that are made of muscle and fibrous tissue that develop in and around the uterus), and chorioamnionitis (a bacterial infection that may occur before or during delivery) may weaken the contractions of the uterine muscles. There are higher risk factors for developing uterine atony, these include placental disorders and bleeding diathesis (an increased tendency for a pregnant woman to bleed or bruise).

Women with one of the risk factors are classified as at medium risk of developing uterine atony while those with two or more are classified as high risk. For pregnant women with known risk factors, uterine atony can be anticipated in advance of childbirth.

Signs and symptoms

The major sign of uterine atony is prolonged or excessive blood loss from the uterus after childbirth. This results from a uterus that remains relaxed without signs of tension or tightness after delivery.

Other signs include:

• low blood pressure
• a fast heart rate
• feeling of dizziness
• lower back pain
• pale appearance
• losing consciousness and
• being unable to pee

If left untreated, there are potential complications. These include:

• anaemia
• extreme fatigue
• low blood pressure causing dizziness or light-headedness and
• an increased risk of haemorrhaging in future delivery

Early detection and intervention can lead to a full recovery. The risk of morbidity increases when there are delays in transporting the patient to the appropriate medical facility, diagnosing the condition, and receiving the proper treatment. Complications usually do not occur if proper, prompt treatment is given. 

Diagnosis

Uterine atony is normally diagnosed when the uterus appears relaxed and soft as well as excessive bleeding after childbirth. This typically involves the doctor placing one hand on the abdomen while the other hand is used to examine the vagina. Blood loss can be estimated by weighing the pad or sponge used to absorb the blood. The medical doctor will perform a physical examination to eliminate other causes of bleeding such as a tear in the vagina or cervix or leftover pieces of the placental tissue in the uterus.

Treatment and management

Uterine atony is a medical emergency and treatment should aim to stop bleeding and replace the lost blood immediately. This includes

• Manual uterine massage – this involves a doctor placing one hand in the vagina to push against the uterus while the other compresses the uterus through the abdomen to promote stronger contractions
• Medications to help the uterus contract and control bleeding (called uterotonic drugs) – including but not limited to oxytocin, prostaglandins, ergot alkaloids, and misoprostol⁵
• When other complications accompany uterine atony, other treatments may be required to replace the blood lost. These treatments include intravenous fluids, blood transfusion and blood products
• Very severe uterus atony may require surgery to tie off the affected blood vessels, uterine artery embolisation (cutting off blood flow to the uterus) and hysterectomy (surgical removal of the uterus) as the last measure, for cases of continuous, severe bleeding or dramatic blood loss

Prevention of uterine atony may not always be possible. For this reason, all stages of labour for women at risk must be properly monitored by doctors. The babies of such women should be delivered in a medical facility where appropriate equipment is available to deal with blood loss.

Well-trained health professionals should always be available. Vital signs and the amount of bleeding that occurs should be continually monitored, to detect haemorrhage. Uterine massage immediately after delivery may reduce the risk of uterine atony.

Medications such as oxytocin given right after birth can help the uterus contract. Iron supplements and other prenatal vitamins can also reduce the complications of uterine atony such as anaemia. These supplements are therefore essential for every pregnant woman.

Complications

Uterine atony is an obstetric emergency that could lead to death if left unattended. Complications include postural hypotension, anaemia, and hypovolemic shock. Hypovolemic shock is a potentially life-threatening complication that involves low blood volume from blood loss.

Symptoms include profuse bleeding, pale skin, fast heart rate, profuse sweating, rapid breathing, and lethargy.

It can also have long-lasting impacts such as post-traumatic stress disorder (PTSD) symptoms and prolonged cardiovascular disease. Following childbirth, some women who experienced uterine atony have also reported the following

• Pain for up to a year after delivery, preventing them from performing simple daily tasks
• Interference with breastfeeding and bonding with their babies, including limited mobility, fatigue, posture problems, and delay in milk production
• Long-term recovery and symptoms of PTSD
• Lack of interest in having further babies in future
• Strain on relationships with their partners including avoidance of physical contact and loss of libido

There is a need for more research on the longer-term health impact of poorly managed uterine atony on the mother and her baby.

Summary

In summary, uterine atony is a critical obstetric condition characterised by the inadequate contraction of the uterine muscles during and after childbirth. This condition can lead to excessive postpartum bleeding, making it one of the top causes of maternal mortality. Understanding the importance of a well-functioning uterus during pregnancy and delivery is crucial in recognizing the risks and signs of uterine atony.

Various risk factors can increase the likelihood of uterine atony, including prolonged labour, multiple pregnancies, the use of certain medications, and existing medical conditions. Prompt diagnosis is essential, as untreated uterine atony can result in severe complications, including anaemia, hypovolemic shock, and even death.

Fortunately, early detection and intervention, such as manual uterine massage and uterotonic medications, can effectively manage uterine atony and prevent severe consequences. In severe cases, surgical interventions may be required. Prevention measures involve careful monitoring during labour, delivering in well-equipped medical facilities, and the administration of uterine-contracting medications.

Additionally, more research is needed to better understand the long-term health impacts of poorly managed uterine atony on mothers and their babies. By raising awareness, improving monitoring, and enhancing medical interventions, we can mitigate the risks associated with uterine atony and ultimately improve maternal and infant health outcomes.