What is uterine atony and what are the first‑line management steps for postpartum hemorrhage caused by uterine atony?

Uterine Atony: Definition and First-Line Management

Uterine atony is the failure of the uterus to contract adequately after delivery, presenting as a soft, boggy uterus, and is the most common cause of postpartum hemorrhage (accounting for 70-80% of cases); immediate management begins with vigorous bimanual uterine massage followed by oxytocin administration. 1, 2, 3

Definition and Clinical Presentation

Uterine atony is a clinical diagnosis characterized by:

• A soft, boggy uterus that fails to contract properly after delivery 3
• The primary physiologic mechanism to control bleeding from the placental bed is sustained myometrial contraction, not the hemostatic system 1
• Accounts for >75% of postpartum hemorrhage cases and is the leading cause of early PPH (within first 24 hours) 1, 2, 3

First-Line Management Algorithm

Step 1: Immediate Physical Intervention

Begin with vigorous bimanual uterine massage to stimulate uterine contractions when a soft fundus is encountered 2, 3. This is the immediate first action before any pharmacologic intervention.

Step 2: First-Line Pharmacologic Treatment

Oxytocin is the cornerstone first-line uterotonic agent for both prevention and treatment of uterine atony 4, 5, 6:

Dosing for postpartum hemorrhage treatment 7:

• Intravenous infusion: Add 10-40 units of oxytocin to 1,000 mL of non-hydrating diluent and run at a rate necessary to control uterine atony 7
• Intramuscular administration: 10 units can be given after delivery of the placenta 7

Oxytocin is more effective than misoprostol and has fewer adverse effects 6.

Step 3: Second-Line Uterotonic Agents

If uterine atony is refractory to oxytocin, administer second-line agents early 2, 5:

Methylergonovine (Methergine) 8, 5:

• Indicated for routine management of uterine atony, hemorrhage, and subinvolution 8
• CRITICAL CONTRAINDICATION: Do not use in hypertensive patients due to risk of severe vasoconstriction and hypertensive crisis 2

Carboprost (15-methyl PGF2α) 5, 9:

• Likely superior to misoprostol as a second-line agent 5
• Can be given as intramyometrial injection (250 micrograms), but must be used early to obtain maximum effect 9

Misoprostol 5, 6:

• Alternative prostaglandin option, particularly useful in resource-poor settings 4
• Less effective than methylergonovine or carboprost 5

Advanced Non-Surgical Interventions

Step 4: Uterine Tamponade

For refractory uterine atony unresponsive to uterotonic agents, use intrauterine balloon tamponade or packing 2, 5. This mechanical intervention can be life-saving before proceeding to surgery.

Step 5: Surgical Options

If medical management and tamponade fail, surgical interventions include 2:

• Bilateral uterine artery ligation
• B-Lynch compression suture or three vertical compression sutures 10
• Hysterectomy for extreme cases 2

Uterine artery embolization may be considered in hemodynamically stable patients who have failed medical management 2.

Critical Concurrent Actions

Active management of the third stage of labor with uterotonics (oxytocin) should be routine to prevent uterine atony 1, 6.

Rule out other causes of bleeding 2, 3:

• Thoroughly inspect cervix and vagina for lacerations (especially if uterus is firm) 2, 3
• Verify complete placental delivery to exclude retained products 3
• Assess for coagulopathy with PT/PTT, fibrinogen, and platelet count 2, 3

Implement massive transfusion protocol early if hemorrhage is severe (>1,500 mL), using packed red cells, fresh-frozen plasma, and platelets at a 1:1:1 ratio 2, 6.

Common Pitfalls to Avoid

• Never use methylergonovine in hypertensive patients - this is an absolute contraindication due to risk of severe hypertension from vasoconstriction 2
• Do not delay second-line agents - they should be administered early when atony is refractory to oxytocin, not after prolonged attempts with oxytocin alone 5, 9
• Do not assume atony is the cause if the uterus is firm - a firm, well-contracted uterus effectively rules out atony, and genital tract laceration becomes the most likely cause 3
• Avoid misdiagnosing amniotic fluid embolism based solely on hemorrhage from persistent atony with secondary coagulopathy 2