The perineum extends from the pubic arch to the coccyx and is divided into the anterior urogenital triangle and the posterior anal triangle. Anterior perineal trauma is injury to the labia, anterior vagina, urethra or clitoris and is usually associated with little morbidity. Posterior perineal trauma is any injury to the posterior vaginal wall, perineal muscles or anal sphincter (Fernando 2007; Kettle 2008).
Perineal trauma can occur spontaneously or result from a surgical incision of the perineum (episiotomy). The incidence of perineal trauma is reported to be 85% (McCandlish 1998) and the incidence of trauma that affect the anal sphincter is 0.5–7.0% (Sultan 1999), usually between 0.5 and 2.5% of spontaneous vaginal deliveries (Byrd 2005). Anal sphincter or mucosal injuries are identified following 3% to 5% of all vaginal births (Eke us 2008). Around 8% of women experience incontinence of stool and 45% suffer involuntary escape of flatus following anal sphincter injury (Eason 2002). Higher rates of perineal trauma are consistently noted in first vaginal births and with instrumental delivery (Christianson 2003).
There is considerable variation in the number of reported rates of perineal trauma between countries, partly due to differences in definitions and reporting practices (Byrd 2005). Studies with restrictive use of episiotomy report rates of perineal trauma that require suturing between 44% and 79% (Dahlen 2007; Soong 2005).
An episiotomy or perineotomy is a surgically planned incision on the perineum and the posterior vaginal wall during second stage of labor. The use of episiotomy has been said to decrease trauma to the fetus, decrease the frequency of extensive perineal tears, and protect the soft maternal tissues. Episiotomy is done as prophylaxis against soft-tissue-trauma.
There are four main types of episiotomy (Fig. 1.1):
- Mediolateral: The incision is made downward and outward from midpoint of fourchette either to right or left. It is directed diagonally in straight line which runs about 2.5 cm away from the anus (midpoint between anus and ischial tuberosity).
- Median: The incision commences from center of the fourchette and extends on posterior side along midline for 2.5 cm.
- Lateral: The incision starts from about 1 cm away from the center of fourchette and extends laterally. There is chance of injury to Bartholin's duct and thus some practitioners have totally condemned it.
- ‘J’ shaped: The incision begins in the center of the fourchette and is directed posteriorly along midline for about 1.5 cm and then directed downwards and outwards along 5 or 7 o'clock position to avoid the anal sphincter. This is also not done widely.