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Postpartum hemorrhage caused by trauma to the birth canal is obvious in most cases. Important exceptions are unrecognized accumulations of blood within the uterus or vagina as well as uterine rupture with intraperitoneal bleeding. Initial assessment strives to differentiate uterine atony from genital tract lacerations. An understanding of predisposing risk factors shown in Table 30-1 can aid this discrimination. It is axiomatic that persistent bleeding despite a firm, well-contracted uterus suggests that hemorrhage most likely is from lacerations. Bright red blood further suggests arterial bleeding. To confirm that lacerations are a source of bleeding, careful inspection of the vagina, cervix, and uterus is essential.
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Sometimes bleeding may be caused by both atony and trauma, especially after forceps- or vacuum-assisted vaginal delivery. Importantly, if significant bleeding follows these types of deliveries, then the cervix and vagina should be carefully examined to identify lacerations. This is easier if epidural or spinal analgesia has been placed for labor and delivery. If no lower genital tract lacerations are found and the uterus is contracted yet supracervical bleeding persists, then manual exploration of the uterus is done to exclude a uterine tear. This is also done routinely after internal podalic version and breech extraction.
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INJURIES TO THE BIRTH CANAL
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Vulvovaginal Lacerations
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Childbirth is invariably associated with some trauma to the birth canal, which includes the uterus and cervix, vagina, and perineum. Injuries sustained during labor and delivery range from minor mucosal abrasions to lacerations that create life-threatening hemorrhage or hematomas.
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Small tears of the anterior vaginal wall near the urethra are relatively common even after the most uncomplicated deliveries, especially in nulliparas. They are often superficial with little or no bleeding, and suture repair is usually not necessary. That said, minor superficial perineal and vaginal lacerations occasionally require sutures for hemostasis. A fine-gauge absorbable suture such as 4-0 gauge plain or chromic gut is suitable. Adequate analgesia is necessary to repair such lesions.
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Deeper perineal lacerations are usually accompanied by varying degrees of injury to the outer third of the vaginal vault. Some extend to involve the anal sphincter or varying depths of the vaginal walls. The frequency of third- and fourth-degree lacerations in more than 87,000 deliveries from the Consortium on Safe Labor database is shown in Table 30-2. Some factors associated with an increased frequency of lacerations are also shown in the table. One of these is parity, and the frequency of these perineal lacerations was 5.7 percent in nulliparas but ...