Are Delayed and Misdirected Episiotomies Predisposing Factors for Pelvic Floor Muscle Dysfunction and Third-degree Tears?

Fabian Imoh-Ita, MD, Avril Fowler

Disclosures

Episiotomy has been one of the most common procedures in obstetrics practice. It is suggested that episiotomy generally increases postpartum blood loss and perineal pain, and, more precisely, midline episiotomies increase the risk of third-degree perineal tear.[1] Liberal as opposed to selective use of episiotomy has been shown to be unwarranted and probably harmful.[2] These concerns may have led to the significant reduction of episiotomy rates in the United States over the past 2 decades.[3]

Selective rather than routine episiotomy policies seem to have a number of benefits, such as less posterior perineal trauma and less suturing, but there is also an increased risk of anterior perineal trauma.[4] This has led to calls for selective episiotomy only when the perineum is threatening to tear in advanced second stage of labor.[5] However, on the basis of principles of elasticity, at that juncture the elastic limits of the pelvic floor tissues would have already been breached and permanently damaged, as demonstrated by stretch marks on overstretched skin. It has been suggested that women without stretch marks have good elasticity and are less likely to tear tissue at childbirth.[6] Awaiting imminent tear of the perineum before an episiotomy may be too late to protect the pelvic floor elastic tone, however, and this could subsequently lead to vaginal prolapse and urinary, fecal, and flatus incontinence. In addition, making an incision at this stage of labor predisposes to a larger tear at the site where the episiotomy was cut as a result of the creation of weak points by the overstretched perineum.

The anatomy of the vulva and pelvic floor is grossly distorted when the fetal head crowns spontaneously or during instrumental deliveries. The vagina is distended to at least 10 cm in diameter, and the anus and anal sphincter are also at full stretch. The vagina and anus at this stage are in closer proximity than during the first or early second stage of labor. As the perineum threatens to tear in the late second stage of labor, misdirected mediolateral episiotomies and midline episiotomies may cause iatrogenic third-degree tears.Selective mediolateral episiotomies done at fetal head crowning, especially with instrumental deliveries, should be at least 2.5 to 3 cm from the anal margin or, as rule of thumb, about 90° from the midline starting from the fourchette. Episiotomies directed at or less than 45° from the midline -- toward the ischial tuberosity or between the ischial tuberosity and midline, as traditionally recommended in an unstretched perineum, would most likely involve the anal sphincter because of the distorted vulva anatomy at this stage of labor.

Accoucheurs who give selective episiotomies as the fetal head crowns the perineum must take into consideration the distorted anatomy of the vulva and perineum in late second stage of labor if iatrogenic third-degree tears are to be avoided. All types of episiotomies should be used selectively, and more research is needed to determine the appropriate time to utilize them without compromising the elasticity of the perineum structures and the risk factors for extended perineal tear.

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