What are the steps to identify the cause of postpartum hemorrhage?

Identifying the Cause of Postpartum Hemorrhage

Begin by systematically evaluating the "Four T's" (Tone, Trauma, Tissue, Thrombin) through a structured clinical assessment that prioritizes uterine tone evaluation first, followed by genital tract inspection, placental completeness verification, and coagulopathy assessment. 1, 2, 3

Initial Clinical Assessment Algorithm

Step 1: Assess Uterine Tone (TONE)

• Palpate the uterus immediately to determine if it is firm and well-contracted versus soft and boggy 2
• Uterine atony accounts for 70-80% of all postpartum hemorrhage cases and is the leading cause of early PPH 2
• A soft, boggy uterus that fails to contract properly confirms atony as the cause 2
• If the uterus is firm, uterine atony is effectively ruled out and you must proceed to evaluate other causes 2

Step 2: Inspect for Genital Tract Trauma (TRAUMA)

• When PPH occurs with a firm, well-contracted uterus, genital tract trauma becomes the leading cause 2
• Perform thorough visual inspection of the cervix, vagina, and perineum for lacerations 1, 2
• Palpate for perineal or vaginal hematomas 1
• Trauma-related hemorrhage (lacerations, uterine rupture, incision extensions) is the second leading cause of PPH overall 2
• Infralevator or perineal hemorrhage can be evaluated on visual inspection, while intra-abdominal hemorrhage may require imaging 1

Step 3: Verify Complete Placental Delivery (TISSUE)

• Examine the delivered placenta for completeness to identify retained products of conception (RPOC) 2, 3
• RPOC complicates approximately 1% of third-trimester deliveries and is the second most common etiology for PPH after uterine atony 2
• Retained placenta is defined as spontaneous placental delivery occurring more than 30 minutes after fetal expulsion 2
• Consider manual exploration of the uterine cavity if placental fragments are suspected 4

Step 4: Assess for Coagulopathy (THROMBIN)

• Evaluate for inherited or acute coagulopathy (amniotic fluid embolism, placental abruption, severe pre-eclampsia, HELLP syndrome) 1
• Coagulopathy is less common but potentially life-threatening 1, 2
• Check for clinical signs: persistent oozing from IV sites, surgical incisions, or mucosal surfaces 3
• Patients with PPH are at high risk for hypofibrinogenemia, with fibrinogen levels <2 g/L occurring in 17% of cases with blood loss exceeding 2000 mL 5

Advanced Diagnostic Imaging (When Clinical Diagnosis is Unclear)

Indications for CT Abdomen/Pelvis with IV Contrast

• Use CT in hemodynamically stable patients when conventional medical treatment has been unsuccessful 1
• CT determines whether active ongoing hemorrhage is present, localizes the bleeding, and identifies the source 1
• There is little clinical utility in noncontrast CT in the setting of active ongoing hemorrhage 1
• CT identifies surgical causes that will not benefit from empiric embolization (uterine rupture, genital tract laceration) 1

CT Findings by Cause

• Uterine atony: Hematoma within the cavity of an enlarged uterus (though this is primarily a clinical diagnosis) 1
• Vascular complications: Bladder flap, subfascial, or perivaginal space hematomas 1
• Uterine dehiscence: >5 cm bladder flap hematoma with disruption of endometrial and myometrial layers but intact serosal layer 1
• Uterine rupture: Gas in the myometrial defect extending from endometrium to parametrial tissue with hemoperitoneum 1

When to Use CTA Abdomen/Pelvis

• Persistent hemorrhage after empiric embolization is an indication for CTA 1
• Active extravasation is seen in 41-74% of PPH cases on CTA 1
• Multiphasic CT (noncontrast, arterial, and portal venous phases) has 97% accuracy for detecting the site of active extravasation 1
• CTA enables comprehensive evaluation of abdominopelvic vasculature including ovarian and inferior epigastric arteries 1

Role of MRI Pelvis

• MRI is not commonly used in significant life-threatening early PPH due to access limitations and time required 1
• MRI is superior to CT and ultrasound in detecting myometrial defects with intact serosal layer in uterine dehiscence 1
• Consider MRI for distinguishing/confirming uterine dehiscence versus rupture when ultrasound or CT findings are inconclusive 1

Common Pitfalls to Avoid

• Do not assume a firm uterus rules out all causes of hemorrhage—systematically evaluate all Four T's 2, 3
• Do not interpret hypodense edema at the cesarean incision site as dehiscence in the first postpartum week—this has low correlation with clinical findings 1
• Do not order noncontrast CT for active hemorrhage—it provides little clinical utility 1
• Do not delay evaluation for coagulopathy if bleeding persists despite addressing tone, trauma, and tissue 3
• Small (<4 cm) subfascial and bladder flap hematomas may not be clinically significant and should not distract from other causes 1