Objective: To emulate a randomized controlled trial investigating if lateral or mediolateral episiotomy compared to no episiotomy reduces the prevalence of obstetric anal sphincter injury (OASIS) in nulliparous women delivered with vacuum extraction. Design: A population-based observational study. Setting: Sweden. Population: 63 654 nulliparous women delivered with vacuum extraction derived from the Swedish Medical Birth Register 2000-2011, with a live singleton baby without known malformations in cephalic presentation in gestational week ≥34+0, and subject to lateral or mediolateral episiotomy or no episiotomy. Methods: The effect of episiotomy was calculated using a causal doubly robust estimation method based on propensity scores. Results are presented as the average treatment effect and numbers needed to treat (NNT). Main Outcome Measures: OASIS (third-and fourth-degree perineal injury) in nulliparous women delivered with vacuum extraction. Results: Episiotomy was associated with a reduction in OASIS from 15.5% to 11.8%, average treatment effect-3.66% (95% CI-4.31 to-3.01) and NNT 27. Third-degree perineal injuries were reduced from 14.0% to 10.9% (-3.08, 95% CI-3.71 to-2.42) with NNT 32. Fourth-degree perineal injuries were reduced from 1.6% to 1.0 % (-0.58%, 95% CI-0.79 to-0.37) with NNT 172. Conclusions: Lateral or mediolateral episiotomy reduced the prevalence of OASIS in nulliparous women delivered with vacuum extraction, compared to women with no episiotomy.

IntroductionObstetric anal sphincter injury (OASIS) occurs in 5%–7% of normal deliveries and increases with vacuum extraction (VE) to 12%–14% in nulliparous women in Sweden. Lateral/mediolateral episiotomy may reduce the prevalence of OASIS at VE in nulliparous women. The current use of episiotomy is restrictive. The protective effect and consequences are uncertain. This trial will investigate if lateral episiotomy can reduce the prevalence of OASIS and assess short-term and long-term effects.Methods and analysisThis is a multicentre randomised controlled trial of lateral episiotomy versus no episiotomy in nulliparous women with a singleton, live fetus, after gestational week 34+0 with indication for VE. A lateral episiotomy of 4 cm is cut at crowning, 1–3 cm from the midline, at a 60° angle. The primary outcome is OASIS by clinical diagnosis analysed according to intention to treat. To demonstrate a 50% reduction in OASIS prevalence (from 12.4% to 6.2%), 710 women will be randomised at a 1:1 ratio. Secondary outcomes are pain, blood loss, other perineal injuries, perineal complications, Apgar score, cord pH and neonatal complications. Web-based questionnaires at baseline, 2 months, 1 and 5 years will be used to assess pain, incontinence, prolapse, sexual function, quality of life and childbirth experience. A subset of women will receive follow-up by pelvic floor sonography and pelvic examination. Mode of delivery and recurrence of OASIS/episiotomy in subsequent pregnancies will be assessed at 5 and 10 years using register data.Ethics and disseminationThe trial is open for enrolment. The trial has received ethical approval from the Regional Ethical Review Board of Stockholm and full funding from the Swedish Research Council. Women are interested in participation. The predominant restrictive view on episiotomy may limit recruitment. Results are of global interest and will be disseminated in peer-reviewed journals and at international congresses.Trial registration numberNCT02643108; Pre-results.

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IntroductionThe number of women postponing childbirth until an advanced age is increasing. Our aim was to study the outcome of labor in nulliparous women ≥40 years, compared with women 25‐29 years, after both spontaneous onset and induction of labor.Material and methodsThe nationwide population‐based Swedish Medical Birth Register was used to study the perinatal outcome in nulliparous women with a singleton, term (gestational weeks 37‐44), live fetus in cephalic presentation and a planned vaginal delivery from 1992 to 2011. We included 7796 nulliparous women ≥40 years and 264 262 nulliparous women 25‐29 years. Prevalence and risk of intrapartum cesarean section, operative vaginal delivery, obstetric anal sphincter injury and a 5‐minute Apgar score <7 were calculated for women ≥40 years stratified for spontaneous onset and induction of labor, using women 25‐29 years as the reference in both strata. Crude and adjusted odds ratios (aOR) were calculated by unconditional logistic regression and presented with 95% confidence intervals (CI).ResultsOverall, 79% of women ≥40 years with a trial of labor reached a vaginal delivery. After spontaneous onset, intrapartum cesarean section was performed in 15.4% of women ≥40 years compared with 5.4% of women 25‐29 years (aOR 3.07, 95% CI 2.81‐3.35). Operative vaginal delivery was performed in 22.3% of women ≥40 years compared with 14.2% of women 25‐29 years (aOR 1.71, 95% CI 1.59‐1.85). After induction of labor, an intrapartum cesarean section was performed in 37.2% women ≥40 years compared with 20.2% women 25‐29 years (aOR 2.51, 95% CI 2.24‐2.81). Operative vaginal delivery was performed in 22.6% of women ≥40 years compared with 18.4% women 25‐29 years (aOR 1.45, 95% CI 1.28‐1.65). The risk of obstetric anal sphincter injury or a 5‐minute Apgar score <7 was not increased in women ≥40 years, regardless of onset of labor.ConclusionsTrial of labor ended in vaginal delivery in 79% of nulliparous women ≥40 years. The risks of intrapartum cesarean section and operative vaginal delivery were higher in women ≥40 years compared with women 25‐29 years, after both spontaneous onset and induction of labor. The risk of obstetric anal sphincter injury or a 5‐minute Apgar score <7 was not increased.