To cut or not to cut? Episiotomy in vacuum extraction

Abstract

BACKGROUND AND AIMS: Obstetric anal sphincter injury (OASIS) may cause anal incontinence, as well as sexual dysfunction and psychological trauma. Mediolateral and lateral episiotomy have been shown to be protective against OASIS in nulliparous women delivered by vacuum extraction (VE). The technique and trigonometric properties of an episiotomy may be important for its protective effect.

The aim of the thesis was to explore episiotomy in Sweden. Firstly, we aimed at investigating the effect of episiotomy in nulliparous women at VE. Secondly, we aimed at exploring the attitudes towards, and knowledge about, episiotomy among doctors. Finally, we wanted to find out if an episiotomy might cause injury to the levator ani muscles (LAM). The impact of advanced maternal age on delivery outcome was also explored.

METHODS AND MAIN RESULTS: Study I and II are register-based cohort studies based on data from the Swedish Medical Birth Register. In study I delivery outcome in women ≥40 years was explored. We compared nulliparous women ≥40 years (n=7796) with nulliparous women 25-29 years (n=264 262) after spontaneous onset and induction of labor between 1992-2011. The rate of OASIS, episiotomy, and low Apgar score was also investigated. We found a significantly higher rate of intrapartum cesarean section among women ≥40 years, both after spontaneous onset of labor (adjusted odds ratio (aOR) 3.07, 95%CI 2.81-3.35) and induction of labor (aOR 2.51, 95%CI 2.24-2.81). The risk of VE was also increased in women ≥40 years, both after spontaneous onset (aOR 1.71 95%CI 1.59-1.85), and induction of labor (aOR 1.45, 95%CI 1.28-1.65). We found no significant difference in rate of OASIS, episiotomy or low Apgar score. Overall, 79% of women ≥40 years had a vaginal delivery compared with 93% of women 25-29 years.

In study II nulliparous women delivered by VE between 2000-2011 were included. Women without episiotomy (n=43 853) were compared to women with a lateral or mediolateral episiotomy (n=19 801). After statistical balancing using propensity score, episiotomy was associated with a reduction in OASIS from 15.5% to 11.8%, ie an average treatment effect -3.7% (95% CI -4.3 to -3.0). The numbers needed to treat (NNT) to prevent one OASIS was 27. The third-degree perineal injuries alone were reduced from 14.0% to 10.9% (-3.1, 95% CI -3.7 to -2.4) with NNT 32. The fourth-degree perineal injuries alone were reduced from 1.6% to 1.0 % (-0.6%, 95% CI -0.8 to -0.4). Fourth-degree perineal injuries required NNT 172.

Study III was a web-based questionnaire sent to the members of the Swedish Society of Obstetrics and Gynecology with a registered email in 2019 (n=2140). The response rate was 25% (n=432). The questionnaire addressed different aspects of VE and episiotomy and contained a picture of a crowning fetal head in which the respondents were asked to depict the episiotomy they would perform in the delivery room. The drawn episiotomies were translated into coordinates in a diagram. The episiotomies were categorized as lateral, mediolateral, midline or unclassifiable. In total, 57.8% (n=222) doctors reported performing episiotomy in less than 50% of VE deliveries. We found that only 54% of the doctors drew what could be considered a protective episiotomy. Furthermore, doctors in Sweden rated episiotomy as the least important measure to prevent OASIS in VE.

Study IV was a descriptive prospective cohort study, examining if lateral episiotomy causes an iatrogenic LAM injury. Sixty-three women delivered by VE who received a standardized lateral episiotomy were examined by 3D endovaginal ultrasound about one year after delivery. Five images were not possible to retrieve due to a broken hard drive, thus 58 women were included. Of these 58 women, 12 had a visible LAM injury (20.7%, 95%CI 10.9-32.9). This is a significantly lower proportion than the stipulated 50% (p<0.001) of women. Two (16.7%, 95% CI 2.1-48.4) of 12 women had an ipsilateral LAD (p=0.02, compared with the stipulated proportion of 50%).

CONCLUSION: In conclusion, trial of labor may be worthwhile in women ≥ 40 years. Episiotomy seems to have a protective effect of OASIS in a Swedish population of nulliparous women with VE. A small majority of doctors in Sweden could depict a protective episiotomy. Our studies support that doctors are able to continue performing lateral episiotomies without risk of cutting the LAM.