Obstetric anal sphincter injury in the second birth after perineal wound complication in the first birth: A nationwide register cohort study.

OBJECTIVE: To investigate whether perineal wound complications in the first birth, alone or in conjunction with obstetric anal sphincter injury (OASI), is associated with an increased risk of OASI in the second birth. DESIGN: Nationwide population-based cohort study. SETTING: Sweden. POPULATION: Women (n = 411 317) with first and second singleton vaginal births in Sweden, 2001-2019. METHODS: Data on diagnostic codes and surgical procedures were retrieved from the Swedish Medical Birth Register and the Swedish Patient Register. A perineal wound complication was defined as wound infection, dehiscence or perineal haematoma within 2 months of childbirth. MAIN OUTCOME MEASURES: Associations between wound complications in the first birth and OASI in the second birth were investigated with logistic regression and presented as adjusted odds ratios (aORs) with 95% confidence intervals (95% CIs). RESULTS: In total, 2619 (0.6%) women had a wound complication in the first birth, and 5318 (1.3%) had an OASI in the second birth. Women with a wound complication but no OASI in the first birth had more than doubled odds of OASI in the second birth (aOR 2.73, 95% CI 2.11-3.53). Women with OASI and a wound complication in the first birth had almost tenfold odds (aOR 9.97, 95% CI 6.53-15.24) of recurrent OASI. CONCLUSIONS: Perineal wound complication in the first birth increases the likelihood of OASI in a subsequent birth.

Pelvic floor dysfunction after intervention, compared with expectant management, in prolonged second stage of labour: A population-based questionnaire and cohort study.

OBJECTIVE: To investigate the effect of vacuum extraction (VE) or caesarean section (CS), compared with expectant management, on pelvic floor dysfunction (PFD) 1-2 years postpartum in primiparous women with a prolonged second stage of labour. DESIGN: A population-based questionnaire and cohort study. SETTING: Stockholm, Sweden. POPULATION: A cohort of 1302 primiparous women with a second stage duration of ≥3 h, delivering from December 2017 to November 2018. METHODS: The 1-year follow-up questionnaire from the Swedish National Perineal Laceration Register was distributed 12-24 months postpartum. Exposure was VE or CS at 3-4 h or 4-5 h, compared with expectant management. MAIN OUTCOME MEASURES: Pelvic floor dysfunction was defined as at least weekly symptoms of urinary incontinence, pelvic organ prolapse or a Wexner score of ≥4. The risk of PFD was calculated using Poisson regression with robust variance estimation, presented as crude and adjusted relative risks (RRs and aRRs) with 95% confidence intervals (95% CIs). The implication of obstetric anal sphincter injury (OASI) on pelvic floor disorders was investigated through mediation analysis. RESULTS: In total, 35.1% of women reported PFD. Compared with expectant management, the risk of PFD was increased after VE at 3-4 h (aRR 1.33, 95% CI 1.06-1.65) and 4-5 h (aRR 1.34, 95% CI 1.05-1.70), but remained unchanged after CS. The increased risk after VE was not mediated by OASI. CONCLUSIONS: Pelvic floor dysfunction was common in primiparous women after a prolonged second stage, and the risk of PFD increased after VE but was unaffected by CS, compared with expectant management. If a spontaneous vaginal delivery eventually occurred, allowing an extended duration of labour did not increase the risk of PFD.

Key outcomes in childbirth: Development of a perinatal core outcome set for management of labor and delivery at or near term.

INTRODUCTION: Consistency and relevance of perinatal outcome measures are necessary basics for obstetric research, audit, and clinical counseling. Still, there is an unwarranted variation in reported perinatal outcomes, which impairs research synthesis, validity, and implementation, as well as clinical benchmarking and longitudinal comparisons. The aim of this study was to develop a short-term perinatal (fetal and neonatal) Core Outcome Set to be used in research and quality assurance of management of labor and delivery at or near term. MATERIAL AND METHODS: The methods were guided by the Core Outcome Measures in Effectiveness Trials Initiative Handbook. The project was prospectively registered on July 2, 2020 in the Core Outcome Measures in Effectiveness Trials (COMET) data base (reference number 1593). A list of potential outcomes was created based on a systematic review of studies evaluating interventions for peripartum management at or near term (≥34 weeks of gestation), including decisions regarding timing and type of onset of labor, intrapartum care, and mode of delivery. The list was entered into a two-round Delphi survey with predefined consensus criteria. Participants (n = 67) included clinicians, researchers, lay persons with experience of childbirth (patient representatives), and other stakeholders. A consensus meeting was held to reach a final agreement. RESULTS: Response rates were 82.1% (55/67) and 92.7% (51/55) for the first and second Delphi rounds, respectively. In total, 17 outcomes were included in the final core outcome set, reflecting mortality, health or morbidity, including asphyxia, central nervous system status, infection, neonatal resuscitation and admission, breastfeeding and mother-infant interaction, operative delivery due to fetal distress, as well as birthweight and gestational age. Two of these outcomes were suggested by patient representatives. CONCLUSIONS: The Swedish Perinatal Core Outcome Set (SPeCOS) study involved a broad circle of relevant stakeholders and reached consensus on a minimal set of perinatal outcomes that should be collected and reported in a standardized way in all future studies on management of labor and delivery at or near term, regardless of the specific population or condition studied. This could improve obstetric research, evidence synthesis, uptake, implementation, and adherence, as well as clinical practice, audit, and comparisons in childbirth care.

The association between episiotomy or OASIS at vacuum extraction in nulliparous women and subsequent prelabor cesarean delivery: A nationwide observational study.

INTRODUCTION: Severe perineal injuries at childbirth affect women's postnatal health, including future childbirths. First births with vacuum extraction carry an increased risk of obstetric anal sphincter injuries (OASIS). Lateral or mediolateral episiotomy at vacuum extraction may decrease the risk of OASIS. Our aim was to assess whether lateral or mediolateral episiotomy, or OASIS, at vacuum extraction in nulliparous women is associated with prelabor cesarean delivery in the subsequent childbirth. MATERIAL AND METHODS: This is a nationwide observational study using data from the Swedish Medical Birth Register, including women having a first birth with vacuum extraction and a second birth in 2000-2014. Both births were live, single, cephalic, ≥34 gestational weeks without malformations. The association between episiotomy or OASIS in the first birth and prelabor cesarean delivery in the second birth was examined using univariate and multivariate logistic regression with inverse probability of treatment weighting, and interaction analysis. Main outcome measure was prelabor cesarean delivery in the second birth. RESULTS: In total, 44 656 women with vacuum extraction at their first birth were included. The rate of prelabor cesarean delivery in the second birth was 5.9% (824 of 13 950) in women with episiotomy, compared with 6.0% (1830 of 30 706) in women without episiotomy. Thus, women with episiotomy did not have an increased risk of prelabor cesarean delivery (adjusted odds ratio [aOR] 1.00, 95% confidence interval [95% CI] 0.83-1.20) compared with women without episiotomy. For comparison, the rate of prelabor cesarean delivery in the second birth was 20.6% (1275 of 6176) in women with OASIS, compared with 3.6% (1379 of 38 480) in women without OASIS (aOR 6.57, 95% CI 5.97-7.23). There was no interaction between episiotomy and OASIS. CONCLUSIONS: Lateral or mediolateral episiotomy at vacuum extraction in nulliparous women did not increase the risk of prelabor cesarean delivery in the subsequent childbirth. OASIS increased the odds of prelabor cesarean delivery more than sixfold.

Interpregnancy interval and maternal and neonatal morbidity: a nationwide cohort study.

This study aimed to assess the association between interpregnancy interval (IPI)-the time from childbirth to conception of the next pregnancy-and maternal and neonatal morbidity. The World Health Organization (WHO) currently recommends an IPI of at least 24 months after a live birth to reduce adverse birth outcomes. However, assessing the relationship between IPI and perinatal outcome is complicated by confounding factors. We conducted a nationwide population-based cohort study using Swedish registry data, allowing for adjustment of maternal characteristics and health at first birth. The study population consisted of all women with a singleton, live, and vaginal first birth with a second singleton birth within five years during 1997-2017, covering 327,912 women and 655,824 neonates. IPI was grouped into six-month intervals with 24-29 months as the reference. The association between IPI and morbidity was examined using multivariate logistic regression. For women having a vaginal delivery at their first birth, intervals < 24-29 months were associated with decreased maternal morbidity and unaffected neonatal morbidity. Intervals > 24-29 months were associated with increased maternal and neonatal morbidity. Our findings question the relevance of WHO's recommendation of an IPI of at least 24 months in a high-income country.

Comparing apples and oranges? Variation in choice and reporting of short-term perinatal outcomes of term labor: A systematic review of Cochrane reviews.

Obstetric research is often criticized for using surrogate or combined outcomes with a disproportionately heavy weight of less relevant components. The objective of this methodological systematic review was to assess the choice and reporting of short-term perinatal outcomes for management of labor at or near term and evaluate if there is any need and possibility to harmonize them. A systematic methodological review of Cochrane reviews was performed. The review was registered prospectively at International Prospective Register of Systematic Reviews (PROSPERO), registration number212954. The Cochrane Database of Systematic Reviews was searched by topics and group browsing and by combination of free-text words and standardized subject terms. Cochrane Systematic Reviews with focus on management of labor at or near term, including timing, type of labor onset, mode of delivery and intrapartum care were included while those focused on prenatal care, postnatal interventions, and preterm deliveries were excluded. Prespecified and reported non-prespecified short-term perinatal (foetal and newborn) outcomes were collected. The outcomes were grouped into domains and classified independently by two authors into five prespecified groups regarding their anticipated importance for patients. Outcomes reflecting how a patient feels, functions, and survives were deemed patient-important. We also evaluated whether any of the outcomes were salutogenic (reflecting positive health and well-being rather than illness or adverse event prevention or avoidance). Our search resulted in 806 Cochrane Systematic Reviews, of which we included 141 published between the years 1996 and 2020. We identified 348 unique outcomes, of which 15 (4.3%) were prespecified and 13 (3.7%) were reported in at least 10% of the reviews. Only half of the prespecified outcomes were reported. In total, 88 (25.3%) of the 348 outcomes were classified as patient important, reflecting how a patient feels, functions, and survives. Salutogenic outcomes were rare (3.4%). To conclude, variation in the choice of outcomes for management of term labor as well as the discrepancy between chosen and reported outcomes were large. Harmonization of perinatal outcome measures, based on consensus between researchers, clinicians, and families, is needed.

Anal incontinence after a prolonged second stage of labor in primiparous women.

The objective was to investigate the effect of delivery mode on anal incontinence 1-2 years after delivery in primiparous women with prolonged second stage of labor. This population-based cohort and questionnaire study performed in Stockholm Region, Sweden, included 1302 primiparous women with a second stage ≥ 3 h from December 1st, 2017 through November 30th, 2018. Background characteristics and outcome data were retrieved from computerized records. Questionnaires based on Wexner score were distributed 1-2 years after delivery. Risk of anal incontinence, defined as Wexner score ≥ 2, was calculated using logistic regression and presented as crude and adjusted odds ratios (OR and aOR) with 95% confidence intervals (CI). Compared with cesarean section, vacuum extraction was associated with anal incontinence (aOR 2.25, 95% CI 1.21-4.18) while spontaneous delivery was not (aOR 1.55, 95% CI 0.85-2.84). Anal incontinence was independently associated with obstetric anal sphincter injuries (aOR 2.03, 95% CI 1.17-3.5) and 2nd degree perineal tears (aOR 1.36, 95% CI 1.03-1.81) compared with no or 1st degree perineal tear. Obstetric anal sphincter injury at vacuum extraction inferred the highest risk of anal incontinence (aOR 4.06, 95% CI 1.80-9.14), compared with cesarean section. Increasing duration of the prolonged second stage did not affect the risk.

A step towards better audit: The Robson Ten Group classification system for outcomes other than cesarean section.

INTRODUCTION: The Robson Ten Group Classification System is widely used for the audit of cesarean section (CS) rates. However, CS rate alone is a poor quality indicator and should be balanced with other obstetric endpoints. The aim of this study was to evaluate whether Swedish national data on obstetric outcomes other than CS, stratified by the Robson classification, could be analyzed in a useful way. MATERIAL AND METHODS: All births in Sweden from 2017 through 2020 recorded in the nationwide Swedish Pregnancy Register were categorized using the Robson classification with subdivision of some groups. Five outcomes were explored: CS, operative vaginal delivery, postpartum hemorrhage, obstetric anal sphincter injury (OASIS) and Apgar score <7 at 5 minuteutes. Rates of each outcome and contribution of each group to the total outcome rate were calculated. RESULTS: The largest Robson groups were nulliparous and multiparous women with single-term cephalic pregnancies, unscarred uterus and spontaneous labor. Intrapartum CS rates were highest for multiple pregnancies, women with induced labor after previous CS, and nulliparous women with induced labor. Nulliparous women and multiparous women with a previous CS with attempted vaginal birth had the highest operative vaginal delivery and OASIS rates. The postpartum hemorrhage rate was highest for multiple pregnancies and transverse lie, followed by prelabor CS in nulliparous and multiparous women with single-term cephalic pregnancies and unscarred uterus. The highest rates of Apgar score <7 at 5 minute were observed in preterm deliveries, multiple pregnancies, transverse lie and breech presentation. The largest contribution to the total CS rate was made by women with previous CS delivered by prelabor CS, and nulliparous women with induced or spontaneous labor. The largest contribution to all other outcomes was made by nulliparous women with spontaneous or induced labor and, notably, multiparous women with spontaneous labor and unscarred uterus. CONCLUSIONS: The Robson classification provides a useful framework for analyzing CS rates along with rates of operative vaginal delivery, OASIS, postpartum hemorrhage and low Apgar score. Parallel interpretation of several outcomes allows a systematic and multidimensional audit, helpful for families and healthcare professionals, and can be used for comparisons, assessment of trends and subpopulations.

Delivery mode and severe maternal and neonatal morbidity among singleton term breech births: A population-based cohort study.

OBJECTIVE: The aim of this study was to examine the association between delivery mode and severe maternal and neonatal morbidity in singleton term breech births. STUDY DESIGN: This nationwide population-based cohort study includes 41 319 singleton term and post-term breech births (37 + 0-42 + 6 gestational weeks) in Sweden from 1998 to 2016. Data was retrieved from the Swedish Medical Birth Register. The primary outcomes were two separate composite outcomes, maternal and neonatal severe morbidity. Secondary outcomes were separate severe maternal and neonatal morbidity outcomes. Hospitalization and out-patient visits during childhood were also analyzed in ages 0-5 years. Logistic regression was used to estimate unadjusted and adjusted odds ratios (aOR) with 95% confidence intervals (CI) of severe maternal and neonatal morbidity in women with vaginal breech birth or intrapartum cesarean section. Women with a prelabor breech cesarean section was used as the reference group. RESULTS: No difference between vaginal delivery and prelabor cesarean section was seen regarding maternal morbidity. Intrapartum cesarean section was associated with elevated odds for maternal morbidity (aOR 1.27, 95% CI 1.10-1.47) compared with prelabor cesarean section. A similar result was observed for vaginal delivery and intrapartum cesarean section combined (aOR 1.29, 95% CI 1.11-1.50). Vaginal delivery was associated with higher odds for composite neonatal morbidity (aOR 1.85, CI 1.54-2.21) and most separate outcomes, as well as increased number of hospital nights and out-patient visits during first year of life, compared with prelabor cesarean section. CONCLUSIONS: Prelabor cesarean section in breech births improved short-term neonatal health without increasing risks for severe maternal short-term complications.

Attitudes and knowledge regarding episiotomy use and technique in vacuum extraction: A web-based survey among doctors in Sweden.

OBJECTIVES: Correct episiotomy use and technique may prevent obstetric anal sphincter injuries. We aimed to explore the attitudes, use, and technique regarding episiotomy among doctors in Sweden, and their willingness to contribute to a randomized controlled trial of lateral episiotomy or no episiotomy in vacuum extraction in nulliparous women. STUDY DESIGN: A web-based survey was sent to members of the Swedish Society of Obstetrics and Gynecology (n = 2140). The survey included 31 questions addressing personal characteristics, use of episiotomy, a two-dimensional picture on which the respondents drew an episiotomy, and questions regarding attitudes towards episiotomy and participation in a randomized controlled trial. We calculated the proportion of supposedly protective episiotomies (fulfilling criteria of a lateral or mediolateral episiotomy and a length ≥ 30 mm). We compared the results between obstetricians, gynecologists, and residents using Chi-square and Kruskal-Wallis tests for differences between groups, and logistic regression to estimate the odds ratio (OR) of drawing a protective episiotomy. RESULTS: We received 432 responses. Doctors without a vacuum delivery in the past year were excluded, leaving 384 respondents for further analyses. In all, 222 (57.8%) doctors reported use of episiotomy in<50% of vacuum extractions. We obtained 308 illustrated episiotomies with a median angle of 53°, incision point distance from the midline of 21 mm, and length of 36 mm, corresponding to a lateral episiotomy. Few doctors combined these parameters correctly resulting in 167 (54.2%) incorrectly drawn episiotomies. Residents drew shorter episiotomies than obstetricians and gynecologists. Doctors ranked episiotomy the least important intervention to prevent obstetric anal sphincter injuries in vacuum extraction. Doctors contributing to an ongoing randomized controlled trial of lateral episiotomy or no episiotomy in vacuum extraction were more able to draw a protective episiotomy (OR 3.69, 95% confidence interval 1.94-7.02). CONCLUSIONS: Doctors in Sweden reported restrictive use of episiotomy in vacuum extraction and depicted lateral type episiotomies, although the majority were incorrectly drawn. Preventive episiotomy was ranked of low importance. Our results imply a need for education, training, and guidelines to increase uptake of correct episiotomy technique, which could result in improved prevention of obstetric anal sphincter injuries.

Episiotomy or not? Midwives' experiences of recruiting to a randomized controlled trial during pregnancy and labor - A qualitative study.

OBJECTIVE: The performance of randomized controlled trials (RCTs) is dependent on recruitment. Recruiting women to RCTs regarding interventions during childbirth may be difficult due to time constraints and their vulnerable situation. Midwives play a major role in such recruitment. Few studies have investigated the views and experiences of recruiters. The aim of this study was to describe midwives' experiences of recruiting pregnant women regarding an RCT of lateral episiotomy or no episiotomy in vacuum-assisted delivery. METHODS: In this qualitative study, 19 midwives were interviewed regarding their experiences. The midwives worked at antenatal health care centers or labor wards. The transcribed interviews were analyzed using content analysis. RESULTS: Four categories appeared during the analysis, including "experiences and perceptions of providing trial information" and "the right timing in providing trial information," which varied among the midwives. Midwives' perceptions of how the women provided consent or declined participation, and the women's views and questions about the randomization and intervention, were summarized as "experiences of how the trial information was received by the women." In the final category, "perceived trial apprehensions and concerns," some midwives described ethical concerns related to the intervention and financial compensation to the staff involved. CONCLUSIONS: Midwives as recruiters would benefit from education and training in incorporating basic and advanced details of trial design and research methods, as well as training and support in recruitment. Awareness and management of the variation among potential recruiters is important when designing and performing an RCT.

COVID-19 in Pregnancy and Early Childhood (COPE): study protocol for a prospective, multicentre biobank, survey and database cohort study.

INTRODUCTION: There is limited knowledge on how the SARS-CoV-2 affects pregnancy outcomes. Studies investigating the impact of COVID-19 in early pregnancy are scarce and information on long-term follow-up is lacking.The purpose of this project is to study the impact of COVID-19 on pregnancy outcomes and long-term maternal and child health by: (1) establishing a database and biobank from pregnant women with COVID-19 and presumably non-infected women and their infants and (2) examining how women and their partners experience pregnancy, childbirth and early parenthood in the COVID-19 pandemic. METHODS AND ANALYSIS: This is a national, multicentre, prospective cohort study involving 27 Swedish maternity units accounting for over 86 000 deliveries/year. Pregnant women are included when they: (1) test positive for SARS-CoV-2 (COVID-19 group) or (2) are non-infected and seek healthcare at one of their routine antenatal visits (screening group). Blood, as well as other biological samples, are collected at different time points during and after pregnancy. Child health up to 4 years of age and parent experience of pregnancy, delivery, early parenthood, healthcare and society in general will be examined using web-based questionnaires based on validated instruments. Short- and long-term health outcomes will be collected from Swedish health registers and the parents' experiences will be studied by performing qualitative interviews. ETHICS AND DISSEMINATION: Confidentiality aspects such as data encryption and storage comply with the General Data Protection Regulation and with ethical committee requirements. This study has been granted national ethical approval by the Swedish Ethical Review Authority (dnr 2020-02189 and amendments 2020-02848, 2020-05016, 2020-06696 and 2021-00870) and national biobank approval by the Biobank Väst (dnr B2000526:970). Results from the project will be published in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04433364.

Characteristics and short-term obstetric outcomes in a case series of 67 women test-positive for SARS-CoV-2 in Stockholm, Sweden.

INTRODUCTION: The Stockholm region was the first area in Sweden to be hit by the pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The national guidelines on the care of women with a positive test for SARS-CoV-2 (detection with polymerase chain reaction [PCR]) recommend individualized antenatal care, mode of delivery based on obstetric considerations, and no routine separation of the mother and the newborn. Breastfeeding is encouraged, and although there is no specific recommendation regarding wearing a face mask to prevent viral transmission to the newborn while nursing, instructions are given to keep high hygiene standards. All studies based on cases tested on hospital admission will capture more women with pregnancy complications than in the general population. Our aim was to describe the clinical characteristics of SARS-CoV-2-positive women and their neonates, and to report short-term maternal and neonatal outcomes. MATERIAL AND METHODS: A retrospective case series with data from medical records including all test-positive women (n = 67) who gave birth to 68 neonates from 19 March to 26 April 2020 in Stockholm, Sweden. Means, proportions and percentages were calculated for clinical characteristics and outcomes. RESULTS: The mean age was 32 years, 40% were nulliparous and 61% were overweight or obese. Further, 15% had diabetes and 21% a hypertensive disease. Seventy percent of the women had a vaginal birth. Preterm delivery occurred in 19% of the women. The preterm deliveries were mostly medically indicated, including two women who were delivered preterm due to severe coronavirus disease 19 (COVID-19), corresponding to 15% of the preterm births. Four women (6%) were admitted to the intensive care unit postpartum but there were no maternal deaths. There were two perinatal deaths (one stillbirth and one neonatal death). Three neonates were PCR-positive for SARS-CoV-2 after birth. CONCLUSIONS: In this case series of 67 women testing positive for SARS-CoV-2 with clinical presentations ranging from asymptomatic to manifest COVID-19 disease, few women presented with severe COVID-19 illness. The majority had a vaginal birth at term with a healthy neonate that was negative for SARS-CoV-2.

Changing diagnostic criteria for gestational diabetes in Sweden - a stepped wedge national cluster randomised controlled trial - the CDC4G study protocol.

BACKGROUND: The optimal criteria to diagnose gestational diabetes mellitus (GDM) remain contested. The Swedish National Board of Health introduced the 2013 WHO criteria in 2015 as a recommendation for initiation of treatment for hyperglycaemia during pregnancy. With variation in GDM screening and diagnostic practice across the country, it was agreed that the shift to new guidelines should be in a scientific and structured way. The aim of the Changing Diagnostic Criteria for Gestational Diabetes (CDC4G) in Sweden ( www.cdc4g.se/en ) is to evaluate the clinical and health economic impacts of changing diagnostic criteria for GDM in Sweden and to create a prospective cohort to compare the many long-term outcomes in mother and baby under the old and new diagnostic approaches. METHODS: This is a stepped wedge cluster randomised controlled trial, comparing pregnancy outcomes before and after the switch in GDM criteria across 11 centres in a randomised manner. The trial includes all pregnant women screened for GDM across the participating centres during January-December 2018, approximately two thirds of all pregnancies in Sweden in a year. Women with pre-existing diabetes will be excluded. Data will be collected through the national Swedish Pregnancy register and for follow up studies other health registers will be included. DISCUSSION: The stepped wedge RCT was chosen to be the best study design for evaluating the shift from old to new diagnostic criteria of GDM in Sweden. The national quality registers provide data on the whole pregnant population and gives a possibility for follow up studies of both mother and child. The health economic analysis from the study will give a solid evidence base for future changes in order to improve immediate pregnancy, as well as long term, outcomes for mother and child. TRIAL REGISTRATION: CDC4G is listed on the ISRCTN registry with study ID ISRCTN41918550 (15/12/2017).

Lateral episiotomy versus no episiotomy to reduce obstetric anal sphincter injury in vacuum-assisted delivery in nulliparous women: study protocol on a randomised controlled trial.

INTRODUCTION: Obstetric 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 ANALYSIS: This 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 DISSEMINATION: The 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 NUMBER: NCT02643108; Pre-results.