Episiotomy Use Among Vaginal Deliveries and the Association with Anal Sphincter Injury: a Population-Based Retrospective Cohort Study

RESEARCH

Episiotomy use among vaginal deliveries and the association with anal sphincter injury: a population-based retrospective cohort study

Giulia M. Muraca PhD MPH, Shiliang Liu MB PhD, Yasser Sabr MD MHSc, Sarka Lisonkova MD PhD, Amanda Skoll MD, Rollin Brant PhD, Geoffrey W. Cundiff MD, Olof Stephansson MD PhD, Neda Razaz PhD MPH, K.S. Joseph MD PhD

n Cite as: CMAJ 2019 October 21;191:E1149-58. doi: 10.1503/cmaj.190366

ABSTRACT

BACKGROUND: The rate of obstetric anal otomy and obstetric anal sphincter trast, episiotomy was associated with sphincter injury has increased in recent injury among women with spontaneous lower rates of obstetric anal sphincter years, particularly among operative vag- and operative vaginal deliveries after injury among forceps deliveries in nul- inal deliveries. We sought to character- controlling for confounders. liparous women (adjusted RR 0.63, 95% ize temporal trends in episiotomy use CI 0.61–0.66), and women with vaginal and to quantify the association between RESULTS: The study population birth after cesarean (adjusted RR 0.71, episiotomy and obstetric anal sphincter included 2 570 847 deliveries. Episiot- 95% CI 0.60–0.85), but not among par- injury. omy use declined significantly among ous women without a previous cesarean operative vaginal deliveries (53.1% in (adjusted RR 1.16, 95% CI 1.00–1.34). METHODS: Using a population-based 2004 to 43.2% in 2017, p < 0.0001) and retrospective cohort study design of spontaneous vaginal deliveries (13.5% INTERPRETATION: Episiotomy use has hospital data from 2004 to 2017, we in 2004 to 6.5% in 2017, p < 0.0001). Epi- declined in Canada for all vaginal studied all vaginal deliveries of single- siotomy was associated with higher deliveries. The protective association ton infants at term gestation in Canada rates of obstetric anal sphincter injury between episiotomy and obstetric anal (excluding Quebec). Rates of obstetric among spontaneous vaginal deliveries sphincter injury among women who anal sphincter injury were contrasted (4.8 with episiotomy v. 2.4% without; gave birth by operative vaginal delivery between women who had an episi adjusted rate ratio [RR] 2.06, 95% confi- (especially forceps) warrants recon otomy and those who did not. Log- dence interval [CI] 2.00–2.11) and this sideration of clinical practice among binomial regression was used to association remained after stratification nulliparous women and those attempt- estimate the association between episi- by parity and obstetric history. In con- ing vaginal birth after cesarean.

bstetric anal sphincter injury, defined as third- and industrialized countries, including Canada,3 Sweden,4,5 Norway,6 fourth-degree perineal laceration, is a maternal morbid- the United Kingdom7,8 and Australia.9 Possible explanations for ity that may occur during vaginal delivery and lead to the increase in such injuries include the rise in maternal age at Oshort- and long-term complications including perineal pain, infec- first birth, which is linked to higher risk of perineal tears, and tion, diminished sexual function, incontinence, abscess formation improved case detection and recording of obstetric injuries.7 and rectovaginal fistulae.1 Obstetric anal sphincter injury is the The risk of obstetric anal sphincter injury differs by type of most common cause of fecal incontinence among women1,2 and, delivery. In 2015, 3.1% of Canadian women had anal sphincter while primary surgical repair after delivery can reduce pelvic floor injury after a spontaneous vaginal delivery.10 However, among dysfunction, the mean rate of anal incontinence reported after operative vaginal deliveries, the risk was substantially higher; primary repair is 39%.2 Over the last 15 years, the rate of obstetric 18.4% of Canadian women had anal sphincter injury after opera- anal sphincter injury has increased by up to 15% in several tive vaginal delivery in 2017.11,12 From 2015 to 2017, operative

© 2019 Joule Inc. or its licensors CMAJ | OCTOBER 21, 2019 | VOLUME 191 | ISSUE 42 E1149 RESEARCH labour). need forrapiddelivery(e.g.,withfetaldistressorprecipitous stage oflabour,previousobstetricanalsphincterinjuryandthe dystocia, breechdelivery,fetalmacrosomia,prolongedsecond results. Indications for episiotomy include nulliparity, shoulder and obstetric anal sphincter injury haveshown inconsistent association between episiotomy use in tially modifiableriskfactor,althoughpreviousstudiesonthe otomy inoperativevaginaldeliveryremainstobeestablished. guideline onintrapartumcareemphasizesthattheroleofepisi vaginal deliveries.Similarly,theWorldHealthOrganization2018 effects ofepisiotomyonanalsphincterinjuryamongoperative anal sphincterinjuryandthatthereisinsufficientevidenceonthe among among vaginaldeliveriesconcludedthatroutineepisiotomyuse E1150 Institute forHealthInformation. obtained fromtheDischargeAbstractDatabaseofCanadian all hospitaldeliveriesinCanada,excludingQuebec,usingdata We carriedoutapopulation-basedretrospectivecohort Methods the UKandAustralia. vaginal deliveryaccountedfor10%–13%ofdeliveriesinCanada, notably lowerintheUnitedStates,at3.1%2015, reduce cesareandeliveryratesareunderway. efforts toincreasetheuseofoperativedeliveryasastrategy tively, andspecificityforbothdiagnoses was99.9%). fourth-degree perineallacerations was97.1%and94.7%,respec- had a high sensitivity and specificity (sensitivity for third- and tors of maternal morbidity, such as obstetric anal sphincter injury, the accuracy of perinatal information in the database. ity assurancechecks.Previousvalidationstudieshaveconfirmed Interventions. prolonged second stage of labour. operative vaginaldeliveriesincludenulliparity,macrosomiaand minimize thenumberofwomenaffected. sphincter injuryamongoperativevaginaldeliveriesisessentialto aimed atreducingthehighandincreasingrateofobstetricanal 1 weeks’ gestation thatresultedin a singleton live birth 41 sphincter injurywithineachofthesestrata. tify theassociationsbetweenepisiotomyandobstetricanal obstetric history and mode of vaginal delivery, and also to quan- poral trends in episiotomy use in Canada, stratified by parity, 10th revision Statistical ClassificationofDiseasesandRelatedHealthProblems , coded usingtheenhancedCanadianversionofInternational notations inthemedicalchartmadebyphysiciansandwere procedures. Diagnosesandproceduresinthedatabaserepresent neonatal outcomesanddetailsofdiagnosesinterventions or maternal characteristics,medicalhistory,labouranddelivery, using standardized definitions. These data included details on nel abstracted information in this database from medical records, Factors associated with obstetric anal sphincter injury among Factors associatedwithobstetricanalsphincterinjuryamong Our studyincludedallvaginal deliveriesbetween37and The objectives of this study were 2-fold: to describe the tem- spontaneous vaginaldeliveriesresultsinhigherratesof 21 ArecentCochranereview 26 (ICD-10-CA) Dataaccuracywasensuredthroughroutinequal- 13–15 Therateofoperativevaginaldeliveryis 25 andtheCanadianClassificationof 24 Trainedhealthrecordsperson- 1,2,18–20 22 operative vaginal delivery CMAJ examiningepisiotomy Episiotomy is a poten | OCTOBER 21, 2019 17 Thus,research 27 27,28 16 study on study on Indica- where 23 - -

| VOLUME 191 that occurinCanada. eral episiotomyaccountsformorethan90%oftheepisiotomies siotomy wasnotincludedinourdatasource.However,mediolat- both midline and mediolateral, as information on thetypeofepi- degree perineallacerations. anal sphincterinjury,whichincludedboththird-andfourth- volume (low,medium orhigh)asaproxymeasure; andthe ery); providerexperienceandcase mixusinginstitutionaldelivery with 1previousvaginaldelivery and1previouscesareandeliv- omy); obstetric history (by stratifying parous women into women to comparewomenwithacomparable indicationforepisiot- analysis todeliverieswithadiagnosis offetaldistressinaneffort v. fourth-degree);confoundingbyindication(byrestrictingthe to thedegree of obstetricanal sphincter injury laceration (third- treat (NNT). adjusted ratedifferencesandthenumberneeded to cmaj.190366/-/DC1. Wequantifiedabsoluteeffectsbycalculating availableatwww.cmaj.ca/lookup/suppl/doi:10.1503/ Table S1, ria, confoundersandoutcomesarelistedinAppendix 1, logic principles. Codes used for the inclusion and exclusion crite- founders on clinical understanding, the literature and epidemio- year ofdelivery.Webasedthedeterminationpotentialcon - labour, epidural anesthesia, infant birth weight, province and maternal age,labourinduction,prolongedsecondstageof attempted, whileadjustingforpotentialconfounders;namely, the pelvicstationatwhichoperativevaginaldeliverywas instruments (forceps, vacuum, sequential instrumentation) and ter injury.Weusedstratifiedanalysestoquantifytheeffectsof the associationsbetweenepisiotomyandobstetricanalsphinc- intervals (CIs) using log-binomial regression models to quantify with thosein2004. ear trendinproportionsbyyearandcomparingrates2017 ment andpelvicstationusingtheCochran–Armitagetestforlin- inal delivery(i.e.,spontaneousandoperative),operativeinstru- we assessedtemporaltrendsinepisiotomyusebymodeofvag ery, andvaginalbirthaftercesareandelivery.Withinthesestrata, nulliparous, parous without a previous cesarean deliv- 3 strata: we categorizedwomenbyparityandobstetrichistoryinto In therestrictedcohortofdeliverieswithinformationonparity, Statistical analysis station: outlet,low-pelvicandmidpelvic. instrument) andgroupedtheminto3categoriesbasedonpelvic applied (forceps,vacuumorsequentialapplicationofeach population withoutinformationonparity. restricted cohortofdeliveriesthatexcluded22%thestudy ric analsphincterinjuryintheoverallcohortandalsowithina episiotomy andtheassociationbetweenobstet- some provinces andtherefore we examined temporal trends in weight. Informationonparitywasnotsystematicallycollectedin those withuncertaininformationonmodeofdeliveryorbirth We excludeddeliveriesbycesarean,inbreechpresentationand between April2004andMarch2018(fiscalyearsto2017). We conducted 5 sensitivity analyses to examine issues related We estimated adjusted rate ratios (RRs) and 95% confidence We stratifiedoperativevaginaldeliveriesbyinstrument | ISSUE 42 29,30 Theprimaryoutcomewasobstetric 21 Episiotomyincluded RESEARCH E1151 operative 31 < 0.0001) and among women among and 0.0001) < p The latter analysis estimates the min analysis estimates The latter 31 ISSUE 42 ISSUE | , episiotomy use varied operative vaginal deliveries, episiotomy use varied operative vaginal deliveries declined from 58.9% in 2004 The a priori level of statistical significance was set at a 2-sided at set was significance statistical of level priori a The Among value of 0.05 for all analyses. We conducted all analyses using analyses. We conducted all analyses using p value of 0.05 for all (SAS Institute Inc., Cary, NC). SAS version 9.4 for Windows having an operative vaginal delivery (–18.6%, p < 0.0001; Appen- dix 1, Tables S4–S7). These trends remained after we stratified women into the 3 parity groups (Figure 2A). Episiotomy use among to 50.4% in 2017 in nulliparous women, from 30.7% to 22.9% among parous women without a previous cesarean delivery, and from 46.8% to 41.6% among women with a vaginal birth after cesarean. Episiotomy rates varied by province, especially among forceps and vacuum deliveries (Appendix 2, Figure S1, available at www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj.190366/-/DC1). Temporal trends in the episiotomy rate between occurred rates episiotomy in declines significant Large, 2004 and 2017 among women having a spontaneous vaginal –51.9%, change (percent delivery robustness of the results to unmeasured confounding using using confounding to unmeasured the results of robustness E-value methodology. Ethics approval the study was obtained from the Clinical Ethics approval for at the University of British Columbia Research Ethics Board (H14–02746). Results deliveries, of which The study included 2 570 847 singleton, term (Figure 1). The rate of 1 998 618 (78%) had information on parity and episiotomy among spontaneous vaginal deliveries 1). (Table respectively 45.9%, and 9.4% was deliveries vaginal was deliveries vaginal spontaneous among rate episiotomy The women with no his- 16.8% in nulliparous women, 5.6% in parous 10.6% in women with vaginal birthdelivery, and tory of cesarean after cesarean. The episiotomy rate in operative vaginal deliveries groups 3 these in respectively, 41.7%, and 24.9% 52.5%, was (Table 2). a rate of 65.4% with depending on operative instrument, with with sequential instru- forceps, 37.6% with vacuum and 67.5% these rates were high- ments. Within each instrument category, no with women parous in lowest and women nulliparous in est women nulliparous Among 2). (Table delivery cesarean of history episiot- delivery, cesarean previous a women without parous and and women older in performed commonly more was omy an episiotomy were women with larger infants. Women who had anesthesia, a pro- more likely to have had an induction, epidural distress (Table 2, and longed second stage of labour and fetal Appendix 1, Table S2). Significant differences in the distribution of maternal, infant and obstetric characteristics are presented using standardized differences in Appendix 1, Table S3. imum strength of association that an unmeasured confounder confounder that an unmeasured of association imum strength anal episiotomy and obstetric to have with both would need regressionthe in confounders the on conditional injury, sphincter association fully. the observed model, to explain VOLUME 191 VOLUME | 9.7 4.0 9.4 15.5 14.5 14.6 14.8 13.4 14.5 11.4 13.3 25.0 12.2 38.3 17.7 14.1 13.5 14.6 25.3 15.9 14.6 45.9 65.4 37.6 67.5 16.2 14.4 15.2 14.4 13.4 Rate, % test for difference in difference for test OCTOBER 21, 2019 OCTOBER 2 | 380 With episiotomy 6198 5365 8698 No. 37 504 53 437 49 978 68 555 15 603 94 016 58 284 12 546 97 057 18 588 59 219 49 388 122 293 149 274 226 196 147 875 324 093 180 315 193 756 280 055 221 647 206 184 374 071 118 272 119 524 167 877 CMAJ 2610 39 941 40 151 89 145 18 588 64 577 840 322 253 484 369 207 591 902 130 426 877 676 709 375 393 222 589 819 365 791 258 058 114 419 410 675 779 305 829 780 369 479 1 027 742 1 978 945 2 440 421 1 474 279 1 096 568 1 981 028 2 205 056 2 570 847 No. deliveries No. 3500–3999 4000–4499 ≥ 4500 2500–2999 3000–3499 Birth weight, g < 2500 Fetal distress Fetal Yes No Prolonged second stage second Prolonged Yes No No Epidural Yes ≥ 45 Parity 1 2–3 ≥ 4 Induction Yes No value for all bivariable comparisons < 0.0001; derived from Χ from < 0.0001; derived comparisons all bivariable for *P value Characteristic Table 1: Numbers and rates of women with an episiotomy an episiotomy with women of and rates 1: Numbers Table infant and maternal and by delivery mode of by vaginal singleton term among all characteristics, 2004–2017* Canada, deliveries, Spontaneous Operative Forceps Vacuum Sequential yr age, Maternal < 20 20–24 25–29 30–34 35–39 40–44 proportion of maternal or infant characteristics among deliveries with and without among deliveries characteristics or infant of maternal proportion group. history and obstetric parity respective in each episiotomy All vaginal deliveries All vaginal

RESEARCH E1152 groups (Appendix 1,TableS8). out anepisiotomyanddeliveries withsequentialinstrumentsinall obstetric analsphincterinjurywas amongforcepsdeliverieswith- .190366/-/DC1). The greatest temporal increase in the rate of www.cmaj.ca/lookup/suppl/doi:10.1503/cmaj at available suppl/doi:10.1503/cmaj.190366/-/DC1 andAppendix4,Figure S3, 3 groups (Appendix 3, Figure S2, available at www.cmaj.ca/lookup/ sphincter injury increased significantly over the study period in all with avaginalbirthaftercesarean.Therateofobstetricanal women withoutapreviouscesareandelivery,and6.7%in eries was4.3%;7.7%innulliparouswomen,1.5%parous The rateofobstetricanalsphincterinjuryamongallvaginaldeliv - with episiotomy Rates ofobstetricanalsphincterinjuryandassociation multiple reasons.Note:CD=cesareandelivery,VBACvaginalbirthafter cesarean. Figure 1:Derivationofstudycohort.Thesumindividualexclusionsmayexceedthetotalateachpointasaresultdeliveries being excludedfor

No. ofnulliparouswome Excluded n • Uncertain parity n CMAJ =850776 =750

| OCTOBER 21, 2019

No. ofdeliveriesincludedin n=750 information onparit No. ofdeliverieswith No. ofwomenwithno restricted cohort

n n n =1999368

=1998618 n previous CD

=1079282 gestation inCanada(excludingQuebec No. ofsingletonlivebirthsat37 No. ofdeliveriesincluded from Apr.1,2004,toMar.31,2018

No. ofparouswomen

y |

VOLUME 191 nonsignificant increased risk of obstetric anal sphincter injury a previous cesarean delivery, episiotomy was associated with a CI 0.61–0.66;Table4).Incontrast, amongparouswomenwithout tion wasstrongerinnulliparous women(adjustedRR0.63,95% deliveries (adjustedRR0.74,95%CI0.71–0.77),andthis associa- episiotomy and obstetric anal sphincter injury among forceps (adjusted RR2.55,95%CI2.42–2.69). in parouswomenwithoutapreviouscesarean,itwasstronger birth aftercesarean,thisassociationwasweaker(Figure3),while 2.11; Table 3). obstetric analsphincterinjury(adjustedRR2.06,95%CI2.00– delivery, episiotomywasassociatedwithincreasedrates of n n n =2570847 =114784 =3525381

In the full cohort, there was a protective association between Among womeninthefullcohortwithaspontaneousvaginal

No. ofdeliverieswithout 2 infullcohort

Excluded • • • •

No. ofwomenwith

| Breech presentation Uncertain modeofdelivery

Uncertain birthweight Caesarean deliveries

information onparity ISSUE 42 vaginal In nulliparouswomenandwithavaginal

n n –41 wk =68560 =57222 VBAC

n =954534 )

n=946594 n=3171 n=309

n=446 0

RESEARCH E1153 9.1 2.1 16.8 16.2 16.2 16.6 17.0 15.3 13.0 15.7 24.9 18.4 14.4 33.1 16.7 10.6 61.5 33.3 62.9 16.6 15.0 16.0 16.9 16.9 15.0 23.8 14.8 13.3 16.4 Rate % 83 15 199 160 363 923 389 136 No. 1580 4371 3767 1163 9853 6342 4898 4959 1387 6281 2284 9424 1963 2843 4497 2490 1816 5891 3023 8820 With episiotomy 11 240 VBAC 577 499 113 1187 9740 6845 1018 4190 6165 2594 6373 3194 9065 27 044 22 726 64 370 48 908 19 652 34 408 34 152 25 152 56 326 17 784 26 654 14 751 12 234 55 724 37 035 68 560 No. deliveries No. 9.9 5.9 6.4 7.0 8.0 5.1 6.6 5.9 6.2 7.7 3.2 4.0 9.3 3.7 1.2 6.6 5.8 7.5 8.4 9.9 7.2 5.6 9.0 6.8 10.9 19.6 48.6 47.1 20.5 Rate % ISSUE 42 ISSUE | 719 440 800 963 154 No. 2168 8019 2568 3845 5126 3479 With episiotomy 26 184 25 831 10 055 20 659 70 408 52 317 41 167 31 809 10 887 13 130 55 264 17 561 29 248 16 968 17 712 57 281 59 046 72 976 VOLUME 191 VOLUME Parous, no previous CD no previous Parous, | 7906 2045 1560 21 971 14 095 13 098 13 750 53 007 37 267 64 555 410 690 371 720 125 098 189 225 135 708 890 057 668 423 410 859 357 759 832 578 129 787 303 427 392 350 201 141 246 704 656 968 1 066 184 1 016 324 1 079 282 No. deliveries No. 0.0 0.0 0.0 34.8 30.5 24.8 26.9 34.9 20.4 23.2 21.3 24.0 43.2 24.6 26.3 25.1 68.9 19.2 29.5 44.5 71.6 22.6 26.1 27.7 31.1 35.5 26.8 16.8 25.5 Rate % test for difference in proportion of maternal or infant characteristics among deliveries with and without episiotomy in with and without episiotomy among deliveries characteristics infant or of maternal in proportion difference for test OCTOBER 21, 2019 OCTOBER 2 | 0 0 0 139 No. 2480 3571 8434 3164 With episiotomy 18 438 90 424 68 037 91 783 34 302 30 014 92 086 38 185 14 270 20 583 63 069 40 491 75 198 63 407 57 151 125 469 187 238 125 166 160 101 107 564 217 252 CMAJ Nulliparous 0 0 0 392 7129 60 461 17 497 69 449 55 403 11 785 74 434 69 782 10 191 365 026 252 678 262 927 147 985 587 849 375 115 781 327 475 661 141 779 178 828 288 212 228 937 213 603 637 173 641 809 850 776 No. deliveries No. 3000–3499 3500–3999 4000–4499 ≥ 4500 Fetal distress, yes distress, Fetal Yes Birth weight, g < 2500 2500–2499 No No stage second Prolonged Yes No Epidural Yes Operative Forceps Vacuum Sequential yr age, Maternal < 20 20–24 25–29 30–34 35–39 40–44 ≥ 45 2–3 ≥ 4 Induction Yes No Parity 1 Spontaneous All vaginal deliveries All vaginal Note: CD = cesarean delivery, VBAC = vaginal birth after cesarean. birth after = vaginal VBAC delivery, CD = cesarean Note: Χ from < 0.0001; derived comparisons all bivariable for *P value Characteristic Table 2: Numbers and rates of women with an episiotomy by mode of delivery and by maternal and infant characteristics, characteristics, and infant maternal and by delivery mode of by an episiotomy with women of and rates 2: Numbers Table 2004–2017* Canada, parity, on information with deliveries vaginal singleton term among all each respective parity and obstetric history group. group. history and obstetric parity respective each

RESEARCH E1154 injury in each province and territory are provided in Appendix 1, women withvaginalbirthaftercesarean (Figure3). 0.91). Noassociationwasfound amongvacuumdeliveryin obstetric analsphincterinjury (adjustedRR0.88,95%CI0.85– vacuum delivery,episiotomywas associatedwithlowerratesof 1.57–1.87; Table4).Conversely,amongnulliparouswomenwith without apreviouscesareandelivery(adjustedRR1.71,95% women, andthisassociationwasstrongerinparouswomen vacuum deliveries with an episiotomy in the full cohort of instruments. pattern wasobservedamongdeliverieswithsequential (adjusted RR1.16,95%CI1.00–1.34;Table4;Figure3).Asimilar ries. Errorbarsdenote95%confidenceintervals.Note:SVD=spontaneous vaginaldelivery. ean (VBAC),singleton,termdeliveries,Canada,2004–2017.Pvalue<0.05fortheCochran–Armitagetestlineartrendinproportions forallcatego- (B) nulliparous (nullip.) women, (C) among parous women without a previous cesarean delivery, and (D) among women with a vaginal birth after cesar- Figure 2:Temporaltrendsinepisiotomyusestratifiedbyparityandobstetrichistoryamong(A)allwomen,modeofdelivery Associations between episiotomy and obstetric anal sphincter Associations betweenepisiotomy andobstetricanalsphincter The rateofobstetricanalsphincterinjurywashigheramong C) Parouswomenwithnopreviouscesareandelivery Rate of episiotomy per 100 deliveries Rate of episiotomy per 100 deliveries A) Allwomen 10 15 20 25 30 35 10 20 30 40 50 60 70 0 5 0 2004 2004 2006 2006 2008 2008 Year Year 2010 Nullip 2010 Forceps CMAJ 2012 2012 VBAC | OCTOBER 21, 2019 Vacuum 2014 2014 No prevCD 2016 2016 SVD | VOLUME 191 forceps, vacuum andsequentialinstruments,respectively. Among nulliparouswomen,adjusted NNTswere10,60,and9for delivery andwomenwithvaginalbirthaftercesarean , respectively. and 32innulliparouswomen, parous womenwithoutcesarean needed toharmamongspontaneousvaginaldeliveries were 85,59 for allgroupsarelistedinAppendix 1,TableS11.Thenumbers Table S10).AdjustedratedifferencesandNNTsbymodeofdelivery substantially whenstratifiedbypelvicstation(Appendix 1, sphincter injuryandtheassociationswithepisiotomydidnotdiffer forceps oruseofsequentialinstruments.Theratesobstetricanal generally loweramongwomenwithepisiotomywhodelivered by in mostregions,whileobstetricanalsphincterinjuryrateswere women afterspontaneousvaginaldeliveriesandvacuum Table S9;ratesofobstetricanalsphincterinjurywerehigheramong Rate of episiotomy per 100 deliveries D) WomenwithaVBAC Rate of episiotomy per 100 deliveries B) Nulliparouswomen 10 20 30 40 50 60 70 80 10 20 30 40 50 60 70 80 0 0 2004 2004 | ISSUE 42 2006 2006 2008 2008 Year 2010 Year 2010 Forceps Forceps 2012 2012 Vacuum Vacuum 2014 2014 2016 2016 SVD SVD RESEARCH

46 E1155 opera- The rou- 22 However, However, or found no or found no spontaneous spontaneous operative vag operative 42,43 7,19,34–41 Several previous observational observational previous Several 33 that combined data from 12 ran- to move away from routine episi- to move away from 22 32 This guideline was reaffirmed in 2018 in reaffirmed was guideline This 12 32 Our analyses add to knowledge in this area by These latter studies failed to stratify women by These latter studies failed to stratify women 22 ISSUE 42 ISSUE | 33,44,45 and it was underpowered to detect any difference in difference in and it was underpowered to detect any The 2017 Cochrane review Despite accumulating evidence of a protective effect of Despite accumulating evidence of a protective effect of The decline in the rate of episiotomy among among episiotomy of rate the in decline The providing estimates of the association between episiotomy and providing estimates of the association between episiotomy and obstetric anal sphincter injury while accounting for these important factors. Our results also show the pronounced decrease in the episiotomy rate among operative vaginal deliveries, suggest- ing that the recommendation is also is also tine use of episiotomy in spontaneous vaginal deliveries and Gynaecol- not recommended by the Society of Obstetricians ogists of Canada (SOGC). and updated in 2019 without any change in recommendations. may have been otomy among spontaneous vaginal deliveries may have been overgeneralized to apply to all vaginal deliveries including operative vaginal delivery, where there may be a benefit. mediolateral episiotomy among operative vaginal deliveries, the SOGC guideline for operative vaginal delivery, published in 2004, recommended that routine episiotomy was not necessary for delivery. vaginal operative studies have shown a protective association between mediolat- studies have shown a protective association among injury sphincter anal obstetric and episiotomy eral tive vaginal deliveries, similar to our findings. obstetric history and did not examine important factors such as pelvic station, indication (e.g., fetal distress) or institutional delivery volume. Similarly, the SOGC guideline for prevention of obstetric anal Similarly, the SOGC guideline for prevention of obstetric anal in women delivering vaginally for the first time for the first time delivering vaginally in women inal deliveries was a 35% to women). There “vaginally nulliparous” (i.e., among injury in obstetric anal sphincter in the rates of 42% reduction an episiot- deliveries with women who had forceps nulliparous The did not have an episiotomy. those who with omy compared in occurrence of obstetric anal sphincter equivalent reduction had vacuum deliveries women who injury among nulliparous Epi- 20%. and 8% between was episiotomy without, versus with, anal obstetric against effect a protective had siotomy also having a vaginal birth after cesarean sphincter injury in women the risk of obstetric anal sphincter injury among among injury sphincter anal obstetric of risk the instruments, and among women with with forceps or sequential 1 previousonly nulliparous vaginal (i.e., delivery cesarean was found in vacuum deliveries. women); the same association women without a previous cesarean However, among parous vacuum delivery with episiotomy conferred delivery, forceps and We risk of obstetric anal sphincter injury. up to a 2-fold higher by hospi- associations varied strength of the also found that the of variations in case tal delivery volume, which is likely a result physician, obstetri- mix, maternity care provider (midwife, family cian) and level of experience (trainee, staff). domized controlled trials examining episiotomy among vaginal among vaginal domized controlled trials examining episiotomy with operative vaginaldeliveries included only 1 trial of women delivery, injury. sphincter anal obstetric association. other studies have contradicted these results other studies have contradicted these observed in our study likely reflects the impact vaginal deliveries observed in our study likely reflects the impact of rou- of randomized trial evidence favouring discontinuation . tine episiotomy among spontaneous vaginal deliveries VOLUME 191 VOLUME | - ARR* (95% CI) ARR* 2.06 (2.00–2.11) 1.19 (1.16–1.21) 0.74 (0.71–0.77) 1.19 (1.16–1.23) 0.87 (0.80–0.94) 2.63 (2.59–2.66) OCTOBER 21, 2019 OCTOBER | CMAJ 4.8 9.6 Yes 15.2 18.1 11.9 24.6 operative vaginal deliveries. Episiotomy and OASI rate (%) rate OASI No 2.4 3.4 13.2 24.3 10.2 28.0 Episiotomy Episiotomy spontaneous vaginal deliveries, episiotomy was associ- Note: ARR = adjusted rate ratio, CD = cesarean delivery, CI = confidence interval, OASI = OASI interval, CI = confidence delivery, CD = cesarean ratio, rate ARR = adjusted Note: injury. anal sphincter obstetric respective within each without episiotomy included deliveries group *The reference women among nulliparous deliveries forceps for group delivery reference (i.e., group Models women). among nulliparous without episiotomy deliveries included forceps of labour, stage second prolonged labour induction, age, maternal for adjusted of birth. and year birth weight, province infant anesthesia, epidural Type of delivery of Type Table 3: Adjusted rate ratios expressing the association the association expressing ratios rate 3: Adjusted Table injury anal sphincter obstetric and episiotomy between Canada, deliveries, vaginal singleton term among all 2004–2017 Operative Operative Forceps Vacuum Sequential Spontaneous Spontaneous All vaginal deliveries All vaginal Among ated with higher rates of obstetric anal sphincter injury, irrespective of parity and obstetric history. Conversely, the association between episiotomy and obstetric anal sphincter injury among operative vaginal deliveries varied markedly. Episiotomy decreased

Interpretation episiotomy of use the in decrease significant a shows study Our among vaginal deliveries of singleton infants at term in Canada, among both spontaneous dix 1, with vaginal birth However, among women S14). Table cesarean after cesarean, restricting to those with only 1 previous those in nulliparous delivery yielded results analogous to volume showed women. The analysis by institutional delivery episiotomy and obstet- that the protective association between deliveries was stronger ric anal sphincter injury among forceps medium delivery in institutions with women among nulliparous low and high deliv- volume compared with those in centres with Rates of obstetric anal S15). ery volumes (Appendix 1, Table sphincter injury among forceps and vacuum deliveries were generally higher in medium- and high-volume versus low-volume institutions. The E-values for key associations between episiotomy and obstetric anal sphincter injury in all the study strata are E-values for the point esti- S16. included in Appendix 1, Table mate and upper 95% confidence bound for obstetric anal sphinc- were delivery forceps a with women nulliparous among injury ter 2.55 and 2.40, respectively. Additional analyses obstetric anal sphinc- The associations between episiotomy and laceration degree of irrespective similar generally were ter injury a diagnosis of S12), (third v. fourth degree; Appendix 1, Table of parous and restriction S13) fetal distress (Appendix 1, Table (Appen delivery vaginal previous 1 only with those to women RESEARCH E1156 episiotomies thatoccurinCanada; incision. Mediolateralepisiotomy accountsformorethan90%ofthe degree perineallaceration(3A v.3B),andangleofepisiotomy type ofepisiotomy(midline v. mediolateral),classofthird- Our studyhasseverallimitations. Welackedinformationonthe Limitations inal delivery. (i.e., onlyifindicated)forbothspontaneousandoperativevag sphincter injury recommends a policy of restricted episiotomy after cesarean. an episiotomyservedasthereferencegroupforallcomparisons.They-axesusealogarithmicscale.Note:CD=cesareandelivery,VBACvaginalbirth (A) allspontaneousvaginaldeliveries,(B)forceps(C)vacuumextractions,and(D)deliveriesusingsequentialinstruments.Womenwithout Figure 3:Adjusted rate ratiosand95%confidenceintervals expressing theassociation between episiotomy and obstetricanalsphincter injury among inal deliveriesacrossCanadalikelyreflectsthis. and thevariationinuseofepisiotomyamongoperativevag is muchroomforinterpretationonthebasisofclinicaljudgment considered tobeanindicationforepisiotomy.However,there are likely represented in the episiotomy group, the protective effect effect are likelyrepresented intheepisiotomygroup, protective

Adjusted rate ratio Adjusted rate ratio C) A) Spontaneousvaginaldelivery 0. 1. 2. 0. 1. 2. 0. 3. 0. 3. 3 0 3 0 2 0 0 2 0 0 Vacuum delivery 47 Thus,anoperativevaginaldelivery,perse,isnot Nulliparous Nulliparous 1.25 0.88 VBAC VBAC 1.00 1.77 29,30 however, as both techniques however,asbothtechniques Parous noCD Parous noCD CMAJ 2.55 1.71 | OCTOBER 21, 2019 A A ll ll women women 2.06 1.19 | VOLUME 191 ing thestudyperiod. change in the recommendations regarding episiotomy use dur sphincter injury. have astrongrelationwithboth episiotomyandobstetricanal unlikely, asinouranalyseseven establishedriskfactorsdidnot unmeasured confounder.Thepresenceofsuchaconfounder is under studycouldbeexplainedonlybyarelativelystrong indicated thattheobservedadjustedRRsforassociations however, thesensitivityanalysisusingE-valuemethodology may havepersisteddespiteadjustmentformanyriskfactors; such aspreviousobstetricanalsphincterinjuryorphysicianskill inclusion ofmedianprocedures. of mediolateralepisiotomymayhavebeenattenuatedbythe We didnotuseatime-seriesanalysis astherewasnomaterial Residual confoundingowingtounmeasuredconfounders Adjusted rate ratio

D) Adjusted rate ratio B) 0. 1. 2. 0. 1. 2. 0. 3. 0. 3. 2 0 0 2 0 0 3 0 3 0 Forceps Sequential instrument Nulliparous Nulliparous | ISSUE 42 delivery 0.66 0.63 32,46 Further,theuse ofacohortdesign VBAC VBAC 0.70 0.71 s Parous noCD Parous noCD 1.51 1.16 Al A ll l women women 0.74 0.87 - RESEARCH -tool E1157 Am J Obstet Am J Obstet ARR* (95% CI) ARR* 1.77 (1.58–1.97) 1.03 (0.93–1.13) 0.71 (0.60–0.85) 1.00 (0.88–1.14) 2.03 (1.90–2.18) 0.70 (0.47–1.05) VBAC 7.2 Yes 16.5 19.1 13.7 11.6 25.9 Episiotomy Core indicators of the health and care of preg- OASI rate (%) rate OASI 4.1 5.7 No 16.2 26.8 13.5 32.2 Episiotomy Parous ISSUE 42 ISSUE | ARR* (95% CI) ARR* 1.83 (1.71–1.96) 1.16 (1.00–1.34) 1.71 (1.57–1.87) 2.55 (2.42–2.69) 3.12 (2.99–3.25) 1.51 (1.18–1.92) Richter HE, Brumfield CG, Cliver SP, et al. Risk factors associated with anal Richter HE, Brumfield CG, Cliver SP, et al. Risk factors associated with anal sphincter tear: a comparison of primiparous patients, vaginal births after delivery. vaginal previous with patients and deliveries, cesarean Gynecol 2002;187:1194-8. Baghestan E, Irgens LM, Bordahl PE, et al. Trends in risk factors for obstetric Baghestan E, Irgens LM, Bordahl PE, et al. Trends in risk factors for obstetric anal sphincter injuries in Norway. Obstet Gynecol 2010;116:25-34. Baumann P, Hammoud AO, McNeeley SG, et al. Factors associated with anal anal with associated Factors al. et SG, McNeeley AO, Hammoud P, Baumann sphincter laceration in 40 923 primiparous women. Int Urogynecol J Pelvic Floor Dysfunct 2007;18:985-90. 2016;38:627-35. European perinatal health report. nant women and babies in Europe in 2015. Euro-Peristat Project; 2018. Avail- able: www.europeristat.com (accessed 2019 Jan. 16). deliv- of method visualisations: data Perinatal collection. data perinatal National ery. Canberra (AU): Australian Institute of Health and Welfare; updated 2019 June 27. Available: www.aihw.gov.au/reports/mothers-babies/perinatal-data -visualisations/contents/data-visualisations (accessed 2019 Jan. 17). Martin JA, Hamilton BE, Osterman MJK, et al. Births: final data for 2015. Natl Vital Stat Rep 2017;66:1-70. Caughey AB, Cahill AG, Guise JM, et al. Safe prevention of the primary cesarean delivery. Am J Obstet Gynecol 2014;210:179-93. 4A0IAQgIYQDiEHADgAt8RUhWq0GjRkAAA (accessed 2019 Jan. 16). 4A0IAQgIYQDiEHADgAt8RUhWq0GjRkAAA (accessed 2019 Cargill YM, MacKinnon CJ. No. 148-Guidelines for operative vaginal birth. J Obstet Gynaecol Can 2018;40:e74-80. Muraca GM, Sabr Y, Brant R, et al. Temporal and regional variations in operative vaginal delivery in Canada by pelvic station, 2004–2012. J Obstet Gynaecol Can Benchmarking Canada’s health care systems: international comparisons — comparisons — Benchmarking Canada’s health care systems: international Information (CIHI); 2013. historical data. Ottawa: Canadian Institute for Health Available: www.cihi.ca /sites/default/files/document/oecd-interactive 16). -historical-data-tables-en-web.zip (accessed 2019 Jan. Information (CIHI). Your health system. Ottawa: Canadian Institute for Health lang=en#/indicator/ Available: https://yourhealthsystem.cihi.ca/hsp/indepth? 048/3/C9056/N4IgKgTgpgdgJgeQG5QmAlgWygYQC4QA2IAXKAM5QAepIAYiAL Laine K, Gissler M, Pirhonen J. Changing incidence of anal sphincter tears in anal sphincter tears in Laine K, Gissler M, Pirhonen J. Changing incidence of four Nordic countries through the last decades. Eur J Obstet Gynecol Reprod Biol 2009;146:71-5. peri- fourth-degree and Third- al. et LC, Edozien DA, Cromwell I, Gurol-Urganci between 2000 and 2012: neal tears among primiparous women in England time trends and risk factors. BJOG 2013;120:1516-25. injuries (OASIS): 11-year Ismail SI, Puyk B. The rise of obstetric anal sphincter (PEDW) data. J Obstet trend analysis using Patient Episode Database for Wales Gynaecol 2014;34:495-8. factors for severe peri- Dahlen H, Priddis H, Schmied V, et al. Trends and risk 2000 and 2008: a neal trauma during childbirth in New South Wales between population-based data study. BMJ Open 2013;3. pii: e002824. 9.2 7.6 2.9 4.3

Yes 11.4 18.9 6. 7. 8. 9. 20. 19. 14. 15. 16. 17. 18. 12. 13. 11. 10. VOLUME 191 VOLUME | Episiotomy No previous CD No previous and and OASI rate (%) rate OASI 5.2 4.4 1.1 1.3 No 10.6 14.4 Episiotomy OCTOBER 21, 2019 OCTOBER | ARR* (95% CI) ARR* 0.90 (0.88–0.93) 0.63 (0.61–0.66) 0.88 (0.85–0.91) 0.66 (0.60–0.72) 1.25 (1.21–1.28) 1.57 (1.55–1.60) CMAJ 6.0 Yes 15.7 18.7 12.7 24.4 10.9 operative vaginal delivery, gener- Nulliparous . Given the opposite associations associations opposite the Given . Episiotomy and OASI rate (%) rate OASI No 4.7 6.7 17.0 28.4 13.8 33.8 Episiotomy Handa VL, Danielsen BH, Gilbert WM. Obstetric anal sphincter lacerations. Handa VL, Danielsen BH, Gilbert WM. Obstetric anal sphincter lacerations. Obstet Gynecol 2001;98:225-30. Sultan AH, Thakar R. Third and fourth degree tears. In: Sultan AH, Thakar R, Fenner DE, editors. Perineal and anal sphincter trauma. 1st ed. London (UK): Springer-Verlag; 2009:33-51. Muraca GM, Lisonkova S, Skoll A, et al. Ecological association between operative vaginal delivery and obstetric and birth trauma. CMAJ 2018;190:E734-41. Ekéus C, Nilsson E, Gottvall K. Increasing incidence of anal sphincter tears Obstet among primiparas in Sweden: a population-based register study. Acta Gynecol Scand 2008;87:564-73. Prager M, Andersson KL, Stephansson O, et al. The incidence of obstetric anal sphincter rupture in primiparous women: a comparison between two European delivery settings. Acta Obstet Gynecol Scand 2008;87:209-15.

Note: ARR = adjusted rate ratio, CD = cesarean delivery, CI = confidence interval, OASI = obstetric anal sphincter injury, OVD = operative vaginal delivery, SVD = spontaneous vaginal vaginal SVD = spontaneous delivery, vaginal = operative OVD injury, anal sphincter = obstetric OASI interval, CI = confidence delivery, CD = cesarean ratio, rate ARR = adjusted Note: cesarean. birth after = vaginal VBAC delivery, included women among nulliparous deliveries forceps for group delivery reference i.e., group; respective within each without episiotomy included deliveries group *The reference infant anesthesia, epidural of labour, stage second prolonged labour induction, age, maternal for Models adjusted women. among nulliparous without episiotomy deliveries forceps of birth. and year birth weight, province Type of of Type delivery Table 4: Adjusted rate ratios expressing the association between episiotomy and obstetric anal sphincter injury among term injury among term sphincter anal and obstetric episiotomy between the association expressing ratios rate 4: Adjusted Table Canada, 2004–2017 on parity, with information deliveries vaginal singleton 3. 1. 4. 5. 2. OVD Forceps Vacuum Sequential SVD All vaginal All vaginal deliveries - spontaneous vaginal deliv episiotomy guidelines for alizing the may cause harm, ery to women with operative vaginal delivery particularly in nulliparous women and women who have a vag inal birth after cesarean delivery. In such women, more liberal use of an adequate mediolateral episiotomy with operative vag inal delivery, especially forceps, may be warranted, given the protective association between episiotomy and obstetric anal sphincter injury.

References between episiotomy and obstetric anal sphincter injury in sphincter injury in between episiotomy and obstetric anal women after spontaneous operative vaginal deliveries vaginal operative Conclusion spontaneous Episiotomy use has declined in Canada among allowed for the adjustment of individual-level confounders, confounders, allowed for the adjustment of individual-level confounding (which is thereby reducing the potential for residual Lastly, we did more likely with ecological time-series analyses). in our statis not include any potential time-varying covariates using delivery of year the included we However, models. tical presented were there- indicator variables and the associations fore adjusted for changes over time. RESEARCH E1158 26. 25. 24. 23. 22. 21. 34. 33. 32. 31. 30. 29. 28. 27.

proposed the study concept and design, and proposed thestudyconceptanddesign, Contributors: Institutet, Stockholm,Sweden and Gynaecology(Stephansson),Karolinska and Children’sHealth,DivisionofObstetrics bia, Vancouver,BC;DepartmentofWomen’s of Statistics(Brant),UniversityBritishColum- Public Health(Lisonkova,Joseph);Department Riyadh, Saudi Arabia; School of Population and and Gynaecology(Sabr),KingSaudUniversity, ada, Ottawa,Ont.;Department ofObstetrics Applied Research, Public Health Agency of Can- Division (Liu), Centre for Surveillance and couver, BC;Maternal,ChildandYouthHealth Joseph), UniversityofBritishColumbia,Van- (Muraca, Sabr, Lisonkova, Skoll, Cundiff, Department ofObstetrics&Gynaecology Karolinska Institutet, Stockholm, Sweden; Razaz), Solna,KarolinskaUniversityHospital, Department ofMedicine(Muraca,Stephansson, Affiliations: ClinicalEpidemiologyUnit, This articlehasbeenpeerreviewed. Competing interests:Nonedeclared. 2019 Jan.17). able: https://secure.cihi.ca/estore/productSeries.htm?pc=PCC189(accessed tenth revision.Ottawa:Canadian Institute for HealthInformation; 2015.Avail- International statisticalclassificationofdiseasesandrelatedhealthproblems: 1997;18:113-9. separation recordsforperinatalsurveillance.ChronicDisCan Wen SW,LiuS,Marcouxetal.Usesandlimitationsofroutinehospitaladmission/ nization; 2018. Intrapartum care for a positive childbirth experience. Geneva: World HealthOrga- vaginal birth.CochraneDatabaseSystRev2017;(2):CD000081. Jiang H,QianX,CarroliG,etal.Selectiveversusroutineuseofepisiotomyfor York: McGraw-HillMedical;2018. Cunningham FG,LevenoKJ,BloomSL,etal.Williams obstetrics. 25thed.New 2008;115:104-8. risk foranalsphincterinjuryduringoperativevaginaldelivery.BJOG de LeeuwJW,WitC,KuijkenJP,etal.Mediolateralepisiotomyreducesthe pilot study.BJOG2008;115:1695-702. versus restrictiveuseofepisiotomyatoperativevaginaldelivery:amulticentre Murphy DJ,MacleodM,BahlR,etal.Arandomisedcontrolledtrialofroutine women. JObstetGynaecolCan2017;39:222. Lee L,DyJ,AzzamH.Management of spontaneous labour atterminhealthy ducing thee-value.AnnInternMed2017;167:268-74. VanderWeele TJ,DingP.Sensitivityanalysisinobservationalresearch:intro- ery versuscaesareandelivery.BJOG2018;125:693-702. mortality amongtermsingletonsfollowingmidcavityoperativevaginaldeliv- Muraca GM,SkollA,LisonkovaS,etal.Perinatalandmaternalmorbidity J ObstetGynaecolCan2016;38:1091-99.e2. agement ofanalsphinctertears—asurveyclinicalpracticeandeducation. Menzies R,LeungM,ChandrasekaranN,etal.Episiotomytechniqueandman- pital harm.Ottawa:CanadianInstituteforHealthInformation;2016. Data quality study ofthe2015–2016DischargeAbstractDatabase:afocusonhos- of theCanadianInstituteforHealthInformation.ChronicDisCan2009;29:96-100. Joseph KS,FaheyJ.ValidationofperinataldataintheDischargeAbstractDatabase htm?pc=PCC189 (accessed2019Jan.17). Health Information;2015.Available:https://secure.cihi.ca/estore/productSeries. . Ottawa: Canadian Institute for Canadian classificationofhealthinterventions.Ottawa:Institutefor Giulia Muraca and K.S. Joseph CMAJ | Health Research. Olof Stephansson is sup- Award fromtheMichaelSmithFoundationfor Sarka LisonkovaissupportedbyaScholar was fundedbyaCIHRgrant(PER-150902). dren’s HospitalResearchInstitute.Thisstudy ship; K.S.JosephissupportedbytheBCChil- Health Research(CIHR)PostdoctoralFellow- the recipientsofCanadianInstitutes Funding: GiuliaMuracaandNedaRazazare accountable forallaspectsofthework. the versiontobepublishedandagreed tant intellectualcontent,gavefinalapprovalof reviewed the manuscript critically for impor- drafted themanuscript.Allofauthors liminary andfinalanalyses.GiuliaMuraca Neda RazazandK.S.Josephreviewedthepre- Sabr, GeoffreyCundiff,OlofStephansson, Lisonkova, AmandaSkoll,RollinBrant,Yasser ducted theanalyses.ShiliangLiu,Sarka the data.GiuliaMuracaandShiliangLiucon- Razaz. GiuliaMuracaandShiliangLiuacquired Cundiff,Olof Stephansson, andNeda Geoffrey Amanda Skoll, Rollin Brant, Yasser Sabr, were assistedbyShiliangLiu,SarkaLisonkova, OCTOBER 21, 2019

| VOLUME 191 35. 47. 46. 45. 36. 44. 43. 42. 41. 40. 39. 38. 37.

prevention, recognition,andrepair.JObstetGynaecolCan2015;37:1131-48. Harvey MA, Pierce M, Walter JE, et al. Obstetrical anal sphincter injuries (OASIS): Gynaecol Can2019;41:870-82. Hobson S,CassellK,WindrimR,etal.No.381—assistedvaginalbirth.JObstet BJOG 2008;115:1688-94. neonatal morbidityinrelationtouseofepisiotomyatoperativevaginaldelivery. Macleod M,StrachanB,BahlR,etal.Aprospectivecohortstudyofmaternaland vent obstetricanalsphincterinjury?EurJObstetGynecolReprodBiol2010;150:142-6. Revicky V,NirmalD,MukhopadhyayS,etal.Couldamediolateralepisiotomypre- episiotomy. during childbirth: role of forceps delivery routinely combined with mediolateral Hudelist G,Gelle’nJ,SingerC,etal.Factorspredictingsevereperinealtrauma 2005;112:941-5. morbidity inrelationtouseofepisiotomyatinstrumentalvaginaldelivery.BJOG Youssef R,RamalingamU,MacleodM,etal.Cohortstudyofmaternalandneonatal eries. JOGC2000;22:583-6. Steed H, Corbett T, Mayes D. The value of routine episiotomy in forceps deliv- women? EurJObstetGynecolReprodBiol2019;232:60-4. obstetric anal sphincter injury during operative vaginal delivery in nulliparous Boujenah J,TigaizinA,FermautM,etal.Isepisiotomyworthwhiletoprevent delivery: aten-yearanalysisofnationalregistry.IntUrogynecolJ2018;29:407-13. episiotomy inpreventingobstetricanalsphincterinjuriesduringoperativevaginal van Bavel J, Hukkelhoven CW, de Vries C, et al. The effectiveness of mediolateral systematic reviewandmeta-analysis.BJOG2015;122:1073-81. Sagi-Dain L,SagiS.Morbidityassociatedwithepisiotomyinvacuumdelivery:a Am JObstetGynecol2014;210:59.e1-6. anal sphincter injury in primiparous women: a population-based cohort study. Jangö H,Langhoff-RoosJ,RosthøjS,etal.Modifiableriskfactorsofobstetric obstetrical analsphincterinjuries.AmJObstetGynecol2012;206:404.e1-5. lateral episiotomy during operative vaginal delivery on theriskofdeveloping de VogelJ,VanDerLeeuw-VanBeekA,GietelinkD,etal.Theeffectofamedio- register-based studyinFinland.BJOG2012;119:1370-8. deliveries andtheriskofobstetricanalsphincterinjuries—aretrospective Räisänen S,Vehviläinen-JulkunenK,CartwrightR,etal.Vacuum-assisted Am JObstetGynecol2005;192:875-81. | ISSUE 42 [email protected] Correspondence to:GiuliaMuraca, Accepted: Sept.16,2019 -data-and-reports/make-a-data-request. process isavailableatwww.cihi.ca/en/ tion onthedataholdingsandrequest process administeredbyCIHI.Moreinforma- decision-makers viaaformaldatarequest able toresearchers,healthmanagersand mation (CIHI).Accesstothesedataareavail- from theCanadianInstituteforHealthInfor- Data sharing:Thesedatawereacquired those oftheauthorsandnotCIHI. sions, and opinions expressed herein are tion (CIHI).However,theanalyses,conclu- by theCanadianInstituteforHealthInforma- Disclaimer: Dataforthisstudywereprovided ogy atKarolinskaInstitutet. Strategic ResearchProgrammeinEpidemiol- 00251), StockholmCountryCouncil,andthe Health, Working Life andWelfare (2015- 2013-2429), theSwedishResearchCouncilfor ported bytheSwedishResearchcouncil(523- access