Description of the condition
Vaginal deliveries are associated with perineal trauma that may be spontaneous (tears) or surgical (episiotomy). Spontaneous tears are defined as first degree and involve the perineal skin only; second degree involves the perineal muscles; third degree involves the anal sphincter complex (classified as 3a where less than 50% of the external anal sphincter (EAS) is torn; 3b where more than 50% of the EAS is torn; 3c where there is injury to the EAS and the internal anal sphincter (IAS)); fourth degree involves the anal sphincter complex (EAS and IAS) and the anal epithelium (RCOG 2007).
The rates of perineal trauma reported after vaginal deliveries vary considerably, partly due to different definitions and reporting practices. The incidence of perineal trauma has been reported to be 85% (McCandlish 1998). Studies indicate that, in vaginal deliveries with limited episiotomy, 51% to 77% of women experienced some form of genital tract trauma that required suturing (Albers 2006; Dahlen 2007; Mayerhofer 2002; McCandlish 1998). The prevalence of severe perineal trauma (third and fourth degree lacerations) in vaginal deliveries is reported to be from 0.5% to 7.0% (Kudish 2008; RCOG 2007), and mostly between 0.5% and 2.5% (Byrd 2005). Perineal trauma, especially third and fourth degree lacerations can result in substantial short- and long-term morbidities that affect large numbers of women worldwide. The morbidities include blood loss (Albers 2006), anal sphincter tears (Andrews 2006), urinary dysfunction (Boyles 2009; Fenner 2003), faecal incontinence (Sultan 2002), sexual problems (Barrett 2000; Radestad 2008; Williams 2007), persistent perineal pain requiring surgical or psychological treatment (Andrews 2007; Macarthur 2004; McCandlish 1998). Moreover, 3% to 5% of all vaginal deliveries sustained anal sphincter tears (Ekeus 2008), and 8% of women experienced faecal incontinence (Eason 2002).
Episiotomy is the surgical enlargement of the vaginal outlet to facilitate the baby's birth during the last part of the second stage of labour. Episiotomy was thought to avoid severe perineal tears (Dannecker 2004; Rodriguez 2008) and easier to repair than a ragged laceration (Carroli 2009). Episiotomy had been introduced around the world without sufficient evidence of its benefits. The episiotomy rate ranged widely worldwide, from 9.70% in Sweden to as high as 100% in Taiwan (Graham 2005; Raisanen 2011). Episiotomy is an important risk factor for perineal trauma, restricting the liberal use of episiotomy can decrease the occurrence of perineal lactations as well as its complications (Carroli 2009; Dannecker 2004; Hartman 2005; Rodriguez 2008).
Furthermore, other risk factors that contribute to perineal lacerations include nulliparity, operative vaginal delivery (particularly forceps delivery), macrosomia (large baby), malposition, epidural anaesthesia, persistent occipitoposterior position, prolonged second stage of labour, induction of labour and shoulder dystocia (Andrews 2006; Carroll 2003; Christianson 2003; Edwards 2006; Eskandar 2009; Fitzpatrick 2003; Goldberg 2003; Hirayama 2012; Kudish 2008; Lowder 2007; Mayerhofer 2002; Nakai 2006; Raisanen 2009; Samarasekera 2009; Soong 2005). Ethnicity (Dahlen 2007; Goldberg 2003) and physical activity (Voldner 2009) may also be associated with perineal trauma.
Description of the intervention
Many perineal techniques are used to prevent perineal trauma. Antenatal perineal massage may lower rates of genital tract trauma (episiotomy, third degree and fourth degree) and ongoing perineal pain (Attarha 2009; Davidson 2000; Kalichman 2008; Stamp 2001). The use of warm compresses on the perineum could decrease the occurrence of perineal lacerations (third degree and fourth degree) (Dahlen 2007; Dahlen 2009) and increase comfort during the second stage of labour (Albers 2006; Sanders 2005). Using vacuum extraction rather than forceps for instrumental deliveries (Fitzpatrick 2003; Weerasekera 2002) could decrease the occurrence of perineal trauma. Perineal guarding (Mayerhofer 2002; McCandlish 1998), active directed pushing (Albers 2006), controlling the fetal head (Downe 2003), maternal position (Altman 2007; Brement 2007; Thies-Lagergren 2011), planned home birth (Radestad 2008), intravaginal use of obstetric gel during the first stage of labour (Schaub 2008) and midwifery model of care (Albers 2005) may also be associated with a reduced occurrence of perineal trauma (Radestad 2008). However, no systematic reviews have been published evaluating perineal hyaluronidase (HAase) injection during the second stage of labour for reducing perineal trauma.
Perineal HAase injection had been widely used to reduce the occurrence of perineal trauma and perineal pain, as well as the need for episiotomy in the 1950s to 1960s (Chatfield 1966; Mink 1955; O'Leary 1965). Reports suggested that the administration of HAase was a simple, low risk, low cost and effective way to produce perineum relaxation, and decrease the necessity of episiotomy without adverse effects (O'Leary 1965). The appropriate dose of HAase for reducing perineal trauma is uncertain. One study found that perineal HAase injection during the second stage of labour with a dose of 20,000 turbidity-reducing units, which was the same as applied in cervical ripening (Spallicci 2007), might significantly decrease the occurrence and severity of spontaneous perineal lactations (Scarabotto 2008). The injection region can be the anterior region of the perineum, the posterior region of perineum, or both.
How the intervention might work
The mechanism of action of HAase has been extensively studied (Menzel 1998), HAase is a enzymatic complex that has the capacity to dissolve (depolymerize and hydrolyze) Hyaluronic acid (HA), which is the major component of the extracellular cement substance of connective tissue, reduce the viscosity of HA and temporarily alter the intercellular cement without permanent damage (Girish 2007). HAase can increase the permeability of cellular membranes and blood vessels (Menzel 1998), relax the connective tissue around the skin or subcutaneous muscles, and render them less vulnerable to mechanical stress or extension during the passage of the fetus through the vaginal canal (Scarabotto 2008).
HAase has been used in many branches of medicine. Previous studies in obstetrics (Spallicci 2007) have revealed that intracervical HAase injections could ripen the uterine cervix, benefit vaginal deliveries, and shorten the labour time, and the use of HAase in the perineum region helps the tissue achieve the necessary relaxation for fetal passage, minimising the numbers of episiotomies.
Why it is important to do this review
Given the high rate of perineal lacerations in primiparas vaginal deliveries and the subsequent morbidities, it is of high importance to identify alternative perineal techniques in order to reduce the perineal trauma and potential associated morbidity during childbirth. The question whether perineal HAase injection can decrease the perineal lacerations has not been satisfactorily answered. Our review aims to evaluate the available evidence about the benefits and side effects of perineal HAase injection for reducing perineal trauma in vaginal deliveries. Perineal HAase may be an efficient and economic method; thus, our review is essential to provide evidence.