Uterine Atony (Atonia uteri)

Uterus atony(Atonia uteri) is a tone disorder that develops when the uterine muscle fibers lose their ability to contract and recoil after placental separation. In the physiological process, uterine contractions following placental delivery compress the spiral arteries to stop bleeding; however, when this mechanism fails, the myometrium becomes flaccid and bleeding becomes uncontrollable. Postpartum hemorrhage (PPH) is defined as blood loss exceeding 500 ml after vaginal delivery and 1000 ml after cesarean delivery. Uterus atony is the most common cause of postpartum hemorrhage, responsible for approximately one quarter of all maternal deaths worldwide. In the literature, causes of postpartum hemorrhage are classified according to the "4T" rule—Tone, Trauma, Tissue, and Thrombin—with uterus atony falling under the category of tone loss and accounting for 75 to 90 percent of all postpartum hemorrhage cases.^【1】

Risk factors that predispose to uterus atony include excessive uterine distension, uterine muscle fatigue, or impaired contractility. Conditions such as multiple pregnancy, polyhydramnios, fetal macrosomia, and high parity increase the risk of atony by causing excessive uterine stretching. Additionally, precipitous labor or prolonged labor can lead to uterine muscle fatigue and subsequent atony. Other risk factors include induction of labor, infections such as chorioamnionitis, uterine fibroids, and a history of atony in previous deliveries. Furthermore, halogenated agents such as halothane used during general anesthesia can relax the uterus and contribute to atony.

^{Uterus Atony (Generated by Artificial Intelligence)}

The characteristic clinical finding of uterus atony is a soft, flaccid, and boggy uterus on palpation. Although bleeding is typically expelled vaginally, it may sometimes accumulate within the uterine cavity, causing the uterus to appear larger than expected and the fundus to rise. Due to the physiological hypervolemia of pregnancy, signs of hypovolemic shock such as tachycardia, hypotension, and decreased urine output may not manifest until blood loss exceeds 1000 ml. During diagnosis, if bleeding persists despite a firm and well-contracted uterus, atony must be ruled out and genital tract trauma must be investigated. The shock index, calculated from the ratio of pulse rate to systolic blood pressure, is a parameter used to assess the severity of bleeding and the need for transfusion.

The most effective approach to preventing uterus atony is active management of the third stage of labor. International guidelines and the World Health Organization recommend three key components of active management:^【2】

• Uterotonic Administration: Administration of oxytocin immediately after delivery of the baby reduces the risk of atony.
• Controlled Cord Traction: While one hand applies counterpressure to the fundus, the other gently pulls the umbilical cord to facilitate placental expulsion during uterine contractions.
• Uterine Massage: Fundal massage is recommended until the uterus is confirmed to be firm. Additionally, immediate skin-to-skin contact and initiation of breastfeeding after delivery stimulate endogenous oxytocin release, aiding uterine involution.

When atony develops, treatment proceeds in a stepwise manner, with medical therapy as the first-line option.

• Oxytocin: The first-line agent for both prevention and treatment of atony; can be administered intravenously or intramuscularly.
• Ergot Alkaloids: Ergot derivatives such as methylergonovine are used when oxytocin is ineffective; however, they are contraindicated in hypertensive patients.
• Prostaglandins: Misoprostol, administered rectally, sublingually, or orally, is effective especially when oxytocin is unavailable or as an adjunct therapy.
• Other Agents: Long-acting oxytocin agonists such as carbetocin and the antifibrinolytic agent tranexamic acid are included in protocols to reduce bleeding. In cases of severe hemorrhage, fibrinogen concentration replacement is administered if levels fall below 2 g/L.^【3】

When medical treatment fails to control bleeding, mechanical methods are employed.

• Uterine Massage and Compression: Bimanual uterine compression, in which one hand forms a fist in the vagina and the other compresses the fundus from the abdomen, is the first mechanical intervention.
• Balloon Tamponade: Balloons such as the Bakri balloon, inserted into the uterine cavity and inflated with sterile fluid, aim to stop bleeding by applying hydrostatic pressure.
• Non-Pneumatic Anti-Shock Garment (NASG): Applies pressure to the lower extremities and abdomen to redirect blood flow to vital organs and aid stabilization.

When conservative measures fail, surgical intervention is required.

• Compression Sutures: Techniques such as B-Lynch, Hayman, and Acar sutures are used to preserve the uterus and avoid hysterectomy. The Acar technique has been reported to reduce blood loss and shorten hospital stay.^【4】
• Arterial Ligation: Bilateral hypogastric or uterine artery ligation is performed to reduce blood flow to the uterus.
• Uterine Artery Embolization: In centers with interventional radiology units, angiographic techniques can be used as an alternative to surgery to occlude bleeding vessels.
• Hysterectomy: As a last resort when all other methods have failed and the mother’s life is at risk, surgical removal of the uterus is performed.

The role of nurses and midwives in cases of uterus atony is critical, from early identification of risk factors to emergency intervention management. Care includes monitoring vital signs every 15 minutes, assessing the firmness and height of the uterine fundus, evaluating blood loss, and ensuring bladder emptying. Within frameworks such as the Human Caring Model, psychological support should be provided to alleviate patient anxiety and establish trusting communication. Coordination with a multidisciplinary team is essential during fluid resuscitation and preparation and administration of blood products.^【5】

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