Pelvic peritoneum

This forms a smooth covering over the uterus and fallopian tubes. Anteriorly it forms the uterovesical pouch and covers the upper surface of the bladder. Posteriorly it forms the pouch of Douglas. Laterally it covers the fallopian tubes and forms the broad ligaments, which do not act as supports.

Pelvic fascia

This connective tissue fills the space between the pelvic organs lining the pelvic cavity walls. Its function is to provide support for the organs, whilst at the same time allowing them to move within the limits of normal function (Verralls 1993). In areas where extra support is needed, it thickens to form the pelvic ligaments:

• Transverse cervical ligaments:

form the principal direct supports of the uterus

are known as cardinal or Mackenrodt’s ligaments

are attached to the vaginal vault and supravaginal cervix

extend transversely in a fan-like way across the pelvic floor to the white line of fascia on the lateral pelvic walls.

• Uterosacral ligaments:

attach to the vaginal vault and supravaginal cervix

pass backwards and upwards from the cervix to the lateral border of the sacral body,

• Round ligaments:

originate just below the cornua of the uterus

pass through the inguinal canal and anterior abdominal wall to become inserted into each labium majus

assist in keeping the uterus in its normal anteverted (forward-tilted) anteflexed (bent on itself) position.

• Pubocervical ligaments:

attach to the inner part of the pubic bones

run posteriorly to form attachments to the bladder, vault of vagina and supravaginal cervix

provide support for the bladder (Verralls 1993).

Deep muscle layer

This is formed mainly from symmetrically paired muscles, varying in thickness, collectively known as the levator ani. They arise at the inner circumference of the true pelvis from the white line of the obturator fascia and decussate midline between the urethra, vagina, and rectum. The muscle fibres pass downwards and backwards and are inserted medially into the upper vagina, perineal body, anal canal, anococcygeal body, coccyx, and lower borders of the sacrum.

The main function is to provide a strong sling to support the pelvic organs and to counteract any increase in the intra-abdominal pressure during coughing and laughing. When the levator ani is contracted, the pelvic floor and perineum are lifted upwards – an important mechanism to maintain continence.

The deep muscles are named after the corresponding fused bones of the innominate bone (pubis, ilium and ischium) (Fig. 40.1):

• Pubococcygeus muscles:

arise from the inner surface of the pubic bones

pass posteriorly below the bladder on either side of the urethra, upper vagina and anal canal to the anococcygeal body and coccyx

fibres cross medially and join those from the opposite sides to form U-shaped slings around the urethra, vagina, and rectum

the puborectalis muscle forms a loop around the anorectal junction and its posterior fibres communicate with the external anal sphincter

medial part is attached to the vagina – no direct attachment to the urethra

on dissection, are paler in colour, suggesting they are fast-twitch muscle capable of rapid contraction (Benson 1992)

function is to provide support to the urethra, vagina, and rectum to control micturition and defecation.

• Iliococcygeus muscles:

arise from the inner border of the white line of fascia on the inner aspects of the iliac bones and the ischial spines

join midline and are inserted posteriorly into the anococcygeal raphe and coccyx

on dissection, are darker in colour, suggesting they are slow-twitch muscles (Benson 1992).

• Ischiococcygeus muscles:

are triangular sheets of muscle and fibrous tissue

arise from the ischial spines, pass downwards and inwards to be inserted into the coccyx and lower part of the sacrum

are sometimes known as the coccygeus muscles

main function is to stabilize sacroiliac and sacrococcygeal joints.

Figure 40.1 Muscles of the pelvic floor seen in the female perineum.

(From Principles of Anatomy and Physiology, 7th edn, by Tortora, G.J. and Grabowski, S.R.

Superficial perineal muscles

These are less important than the levator ani muscles; but contribute to the overall strength of the pelvic floor and likely to be damaged during vaginal delivery (Fig. 40.1):

• Bulbospongiosus muscles (previously Bulbocavernosus in older texts):

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extend from central point in the perineal body, and encircle the vagina and urethra before inserting anteriorly into the corpora cavernosa of the clitoris

posteriorly some fibres merge with the superficial transverse muscle and external anal sphincter

situated beneath bulbocavernosus are the vestibular bulbs anteriorly and Bartholin’s glands posteriorly

main function is to cause erection of the clitoris and contraction of the vagina during sexual activity.

• Ischiocavernosus muscles:

arise from ischial tuberosities

pass upwards and inwards along the pubic arch and are inserted into the corpora cavernosa of the clitoris

some fibres interweave with those forming the membranous sphincter of the urethra.

• Transverse perineal muscles:

arise from ischial tuberosities

pass transversely to converge at central point of the perineum

fibres of each transverse muscle unite and interweave with the superficial tissue of the perineal body and external anal sphincter

provide additional support transversely across the perineal region, helping fix the position of the perineal body.

Sphincters

• Membranous sphincter of the urethra:

arises from one pubic bone

passes above and below the urethra to the opposite pubic bone

not a true sphincter but capable of contracting to occlude the lumen of the urethra.

• External anal sphincter (EAS):

teardrop-shaped circle of muscle

surrounds the anus and is subdivided into three parts (not easily defined during dissection)

– subcutaneous

– superficial

– deep

in females, the EAS is shorter anteriorly and fuses with the bulbocavernosus and transverse perinei in the lower part of the perineum (Sultan et al 1994a)

the deep EAS is inseparable from the puborectalis muscle and posteriorly is attached to the coccyx by some of its fibres

the circular striated (voluntary) muscle of the EAS, when dissected or torn, looks similar to ‘dark red meat’

main function is to close the anal canal lumen and control voluntary passage of faeces and flatus.

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• Internal anal sphincter (IAS):

a condensation of the circular smooth muscle of the rectum

approximately 3–4 cm long and 2–3 mm thick in younger women

not easily defined

on dissection, is paler in colour than the external anal sphincter

main function is to close the lumen of the anus and to prevent involuntary passage of faeces and flatus (very important during sleep).

Ischiorectal fossa

is a deep wedge-shaped area, filled with fat, bounded by the gluteus maximus, anal sphincter, transverse perinei and bulbocavernosus muscles. It is a potential area for haematoma formation.

Subcutaneous fat and skin

Neither has any supporting function.

Prevalence

Over 85% of women who have a vaginal birth will sustain some form of perineal trauma (McCandlish et al 1998) and up to 69% of these will require stitches (McCandlish et al 1998, Sleep et al 1984).

Rates will vary considerably according to individual practices and hospital policies throughout the world, illustrated by wide variations in episiotomy rates internationally from 8% in the Netherlands, 13% in England and 43% in the USA, to 99% in the Eastern European countries (Graham & Graham 1997, Graves 1995, Statistical Bulletin 2003, Wagner 1994).

Certain intrapartum interventions or alternative forms of care may also affect the rate and extent of perineal trauma; including continuous support during labour, delivery position, epidural anaesthesia, style of pushing, restricted use of episiotomy and ventouse delivery (Kettle 1999, 2001).

Aetiology and risk factors

Perineal trauma occurs during spontaneous or assisted vaginal delivery and is usually more extensive after the first vaginal birth (Sultan et al 1996). Women who have no visible damage may be subject to transient pudendal or peripheral nerve injury due to prolonged active pushing or pressure exerted by the fetal head on the surrounding structures (Allen et al 1990).

Associated risk factors include:

Other maternal factors are:

Short- and long-term effects

In the UK, approximately 23–42% of women will have perineal pain and discomfort up to 10–12 days following vaginal delivery and 7–10% of these women will continue to have long-term pain up to 18 months post partum (Glazener et al 1995, Gordon et al 1998, Grant et al 2001, McCandlish et al 1998, Mackrodt et al 1998, Sleep et al 1984).

In terms of sexual function, 62–88% of women will resume intercourse by 8–12 weeks postpartum, though 17–23% of women experience superficial dyspareunia at 3 months after delivery and 10–14% will continue to have pain at 12 months (Barrett et al 2000, Glazener 1997, Gordon et al 1998, Grant et al 2001, Kettle et al 2002, Mackrodt et al 1998).

Estimation of the extent of urinary and faecal incontinence is difficult because of under-reporting of these problems due to the sensitive nature of the complaint (Sultan et al 1996). One survey found that 15.2% of participating women (number 1782) reported stress incontinence which started for the first time within 3 months of the baby’s birth, and 75% of these still had problems over a year later (MacArthur et al 1993). Sleep & Grant (1987) and MacArthur et al (1997) found that up to 4% of women reported occasional loss of bowel control.

Cervical tears

A cervical tear may result if an instrumental delivery (forceps or ventouse) is attempted before the cervix is fully dilated or the woman forcibly pushes the fetus through a cervix that is incompletely dilated (Oats & Abraham 2010).

Bleeding is usually very severe and will persist despite the uterus being well contracted. Postpartum haemorrhage (PPH) resulting from a cervical tear must be managed appropriately and efficiently according to guidelines (NICE 2007), as mismanagement can cause maternal mortality (see Ch. 68). Once the maternal condition has been stabilized, a skilled operator must repair the cervical tear in a theatre with good lighting, appropriate assistance, and adequate anaesthesia.

Timing of the incision

An episiotomy must only be made when the presenting part is distending the perineal tissues; otherwise it will fail to accelerate delivery and excessive bleeding may occur.

Indications

The following are not absolute, and clinical discretion must always be used:

NB: There is no scientific evidence to support the routine procedure of episiotomy to prevent intracranial haemorrhage in preterm deliveries (Woolley 1995).

Risks

NB: The risks are clearly increased with a high episiotomy rate.

Prior to performing the episiotomy, the midwife must prepare the delivery trolley and equipment according to the practice policies and guidelines of the individual employing policies. Safety glasses and gloves must be worn during all obstetric procedures, to protect the operator against HIV and hepatitis infection. The woman’s dignity and comfort must be maintained throughout the procedure (see Table 40.1). There is some debate about the incision to be used – please see website.

Table 40.1 Procedure for mediolateral episiotomy

Complications

Episiotomy rate

There seems to be no consensus as to the recommended episiotomy rate. The World Health Organization suggests that an episiotomy rate of 10%, for normal deliveries, would be ‘a good goal to pursue’ (WHO 1996).

Discussion

Episiotomy has been described as the unkindest cut, but with limited evidence about use and efficacy, has been introduced into maternity care in the UK (see website).

Major variations in current national rates indicate uncertain justification for this practice (Audit Commission 1997).

Some argue that episiotomy causes more pain, weakens pelvic floor structures, interferes with breastfeeding and increases sexual problems (Greenshields & Hulme 1993, Kitzinger & Walters 1981). Others argue that episiotomy reduces the incidence of severe perineal trauma and prevents overstretching of pelvic floor muscles, so reducing the risk of stress incontinence and uterine prolapse (Donald 1979, Flood 1982). However, research carried out by Klein et al (1994) found that women who delivered with an intact perineum or spontaneous perineal tear had less pain, stronger pelvic floor muscles, and better sexual function when compared to those with an episiotomy, at 3 months postpartum.

Midwives should restrict the use of episiotomy to specific fetal and maternal indications. Previous randomized controlled trials comparing restricted to liberal use of episiotomy found that a restricted policy is associated with lower rates of posterior perineal trauma, less suturing, and reduction in pain and healing complications (Carroli & Belizan 2001). This results in a lower rate of maternal morbidity and may have significant cost-saving implications for suture materials (Carroli & Belizan 2001, Sleep et al 1984).

Suture materials for primary repair of perineal trauma

The ideal suture material should cause minimal tissue reaction and be absorbed once it has served its purpose of holding the tissue in apposition during the healing process (Taylor & Karran 1996). Well-aligned perineal wounds heal by primary intention with minimal complications, usually within 2 weeks of suturing. However, if the stitches remain in the tissues for longer than this period, they act as a foreign body and may impair healing, causing irritation. Local infection of the stitches will prolong the inflammatory phase and cause further tissue damage, which will delay collagen synthesis and epithelialization (Flanagan 1997).

Perineal repair using absorbable synthetic material, such as polyglactin 910 (Vicryl) or polyglycolic acid (Dexon), reduces short-term pain, though long-term effects are less clear and there are some concerns regarding the need to remove sutures up to 3 months after delivery (Kettle & Johanson 2001).

Three randomized controlled trials (RCTs) – carried out by Gemynthe et al (1996), McElhinney et al (2000) and Kettle et al (2002) – compared rapidly absorbed polyglactin 910 (Vicryl Rapide) to standard polyglactin 910 (Vicryl) and found no overall difference in short-term perineal pain between groups, but a significant reduction in the need for suture removal up to 3 months following childbirth with the rapidly absorbed material. Two of the trials (Gemynthe et al 1996, Kettle et al 2002) found a significant reduction in ‘pain when walking’ at 10–14 days postpartum. One trial (McElhinney et al 2000) reported a reduction in superficial dyspareunia at 3 months postpartum. This evidence suggests that Vicryl Rapide is the ideal suture material for perineal repair (NICE 2007).

The arguments for recommended suture techniques for primary repair of perineal trauma are given on the website.

Non-suturing of perineal skin

Two RCTs compared suturing the vagina and perineal muscles, leaving the perineal skin unsutured, to the conventional method of suturing the vagina, perineal muscles and skin (Gordon et al 1998, Oboro et al 2003). The UK study found no significant difference in perineal pain at 10 days postpartum between groups (Gordon et al 1998), though the Nigerian study indicated a reduction in perineal pain at 48 hours, 14 days, 6 weeks, and 3 months following birth when the skin was left unsutured (Oboro et al 2003).

Tissue adhesive

Two small trials looked at the use of tissue adhesive for closure of perineal skin following second-degree tear or episiotomy (Adoni & Anteby 1991, Rogerson et al 2000). Both trials claim that this method is effective, but the results must be interpreted with caution owing to the poor methodological design of these studies and the small number of participants included.

Procedure (see Table 40.2)

Perineal tears and episiotomies are repaired under aseptic conditions with a good source of light and the mother in a comfortable position so that the trauma can be easily visualized. Lithotomy poles to support the woman’s legs during the repair are unnecessary and might bring back ‘locked in’ memories of sexual abuse, making the woman feel helpless and out of control (Walton 1994). Also, leg restraints (lithotomy poles) cause flexion and abduction of the woman’s hips which results in excessive stretching of the perineum, causing the episiotomy or tear to gape (Borgatta 1989). Apart from being uncomfortable for the woman, this can make the trauma difficult for the operator to realign and suture. There is no need to use a tampon.

Table 40.2 Procedure for continuous method of perineal repair

If the woman has a working epidural, it may be topped up to provide effective perineal area anaesthesia instead of injecting local anaesthetic. Khan & Lilford (1987) recommend that even if an epidural is used, the perineal wound should be infiltrated with normal saline or local anaesthetic to mimic tissue oedema and prevent overtight suturing.

Prior to performing the repair, the midwife must prepare the suturing trolley and check equipment according to individual employing authorities’ practice guidelines. The woman’s comfort and dignity must be maintained throughout the procedure.

The area should be cleaned according to the individual unit’s guidelines; however, a study by Calkin (1996) found that tapwater was just as effective as chlorhexidine antiseptic.

The method of performing the repair is shown in Figure 40.3 and the rationale for each stage of the process is given in Table 40.2.

Figure 40.3 Continuous non-locking method of perineal repair.

On completion of perineal repair, the woman should be given advice regarding:

Identification of anal sphincter injury

For further information on third- and fourth-degree repair, please see website.