The pregnant uterus, vagina, and vulva have rich vascular supplies that are at risk of trauma during the birth process, and trauma may result in formation of a hematoma. Puerperal hematomas occur in 1:300 to 1:1500 deliveries and, rarely, are a potentially life-threatening complication of childbirth [1,2].
Most puerperal hematomas arise from bleeding lacerations related to operative deliveries or episiotomy; however, a hematoma may also result from injury to a blood vessel in the absence of laceration/incision of the surrounding tissue (eg, pseudoaneurysm, traumatic arteriovenous fistula) [1,3-6]. Women at increased risk of developing puerperal hematomas include those who are nulliparous or who have an infant over 4000 grams, preeclampsia, prolonged second stage of labor, multifetal pregnancy, vulvar varicosities, or clotting disorders [3,7-9].
The most common locations for puerperal hematomas are the vulva, vaginal/paravaginal area, and retroperitoneum.
Vulva — Most vulvar hematomas result from injuries to branches of the pudendal artery (inferior rectal, perineal, posterior labial, and urethral arteries; the artery of the vestibule; and the deep and dorsal arteries of the clitoris) that occur during episiotomy or from perineal lacerations (figure 1) [1,3]. These vessels are typically located in the superficial fascia of the anterior (urogenital) or posterior pelvic triangle (figure 2). The superficial compartment of the anterior triangle communicates with the subfascial space of the lower abdomen below the inguinal ligament. Extension of bleeding in the anterior triangle is limited by Colles' fascia and the urogenital diaphragm, while the anal fascia limits extension of bleeding in the posterior triangle. As a result, bleeding is directed toward the skin where the loose subcutaneous tissues afford little resistance to hematoma formation. Superficial hematomas can extend from the posterior margin of the anterior triangle (at the level of the transverse perineal muscle) anteriorly over the mons to the fusion of fascia at the inguinal ligament. Necrosis caused by pressure and rupture of the tissue surrounding the hematoma may lead to external hemorrhage .
Vaginal/paravaginal area — Vaginal/paravaginal hematomas result from injuries to branches of the uterine artery, mainly the descending branch (figure 3) [1,9]. These hematomas are commonly associated with forceps delivery, but may also occur during spontaneous delivery.