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11 - DOES EPISIOTOMY REDUCE THE RISK OF OASIS? MULTIVARIATE LOGISTIC REGRESSION ANALYSIS OF RISK FACTORS FOR OASIS

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DOES EPISIOTOMY REDUCE THE RISK OFOASIS? MULTIVARIATE LOGISTIC REGRESSION ANALYSIS OF RISK FACTORS FOROASIS

G. THIAGAMOORTHY1, A.ALI 1, S. SHARAFUDEEN 1, G. ARAKLITIS 2,J. E. HUNTER 1, D. ROBINSON 1, L. CARDOZO 1;
1King's Coll. Hosp., London, United Kingdom, 2KingsColl. Hosp., London, United Kingdom.

Introduction: Obstetric analsphincter injuries (OASIS) are associated with significant morbidity.In the UK, the reported rate of OASIS (primiparous, singleton, term,cephalic) has tripled from 1.8% to 5.9% [1]. The Royal College ofObstetricians and Gynaecologists (RCOG) suggests risk factors forOASIS include Asian ethnicity, nulliparity, birth weight greater than4kg, shoulder dystocia, prolonged second stage of labour andinstrumental delivery [2]. Evidence suggests the likelihood of OASIScan be reduced if clinicians provide perineal protection at crowningand warm compression during second stage of labour. The role ofepisiotomy in reducing the risk of OASIS is unclear and the RCOGguidance only states that the protective effect of episiotomy onOASIS is seen at instrumental delivery [2]. Epidural analgesia iscommonly used as a form of intrapartum pain management around theworld. A Cochrane review in 2012 reported that in comparison to othernon-pharmacological and pharmacological methods of pain relief,epidural analgesia is the most effective form of pain management inlabour [3]. The National Institute for Health and Care Excellence(NICE) guidelines on epidurals states that both the benefits and thedisadvantages of the procedure should be explained to women,including the prolonged time of labour and the increased possibilityof vaginal instrumental birth. It has been extrapolated however, thatthis may mean the women are at increased risk of OASIS. Currentlythere is limited data, which looks at the effect of epidurals onOASIS.
Objective: The objectives were to assess theimpact of mediolateral episiotomy and epidurals on the risk of OASIS.Other risk factors for OASIS including maternal age and use offorceps as a second instrument were assessed.
Methods:Contemporaneously recorded antenatal and intrapartum data from 48,831women who were delivered consecutively in our obstetrician led unitwere analysed. Our study cohort consisted of a diverse ethnicpopulation in an inner city environment. Perineal trauma wasdiagnosed clinically and classified according to the RCOGrecommendation. All women who delivered by caesarean section wereexcluded. Statistical analyses were performed using the SPSS (Version22.0. Armonk, NY: IBM Corp). Binary multivariate logistic regressionanalysis was used to identify the independent risk factors associatedwith OASIS. Many risk factors were assessed including:-use ofepidural and other analgesia in labour-mediolateral episiotomy-age atdelivery-method of assisted vaginal delivery (forceps, vacuum,forceps after failed vacuum)
Results: From November 2007 toNovember 2016, 48,831 live births and 1271 OASIS were documented. Themean age of women was 31 years (range, 14 - 51 years), with anaverage body mass index of 26 at booking (range, 13-67). Table 1illustrates the features of the cohort.

Featuresof the study cohort


n

%of all deliveries


Livebirths November 2007 - November 2016

48,831

100



Vaginaldeliveries


36,204

74.1



Caesarean


12,627

25.9



%of all vaginal deliveries



Spontaneousvaginal delivery


29,189

80.6



Instrumentaldelivery


7015

19.4



Instrumentaldelivery

No.Forceps

1767(4.9%)

No.Vacuum extractor

4369(12.1%)

No.Forceps/Failed vacuum

816(2.3%)

No.Vacuum/Failed forceps

63(0.2%)



Perinealtrauma

OASIS

11271(3.5%)

No.Second degree perineal tears

10,064(27.8%)

No.First degree perineal tears

5126(14.2%)

No.Episiotomies

7041(19.5%)

Notrauma/graze only

12702(35.1%)


Analgesiafor labour

No.Hypnotherapy/Aromatherapy/Massage/TENS

8987(24.8%)

No.Entonox, Paracetamol, Codeine

15,874(43.8%)

No.Epidural

8611(23.7%)

No.Pethidine

2842(7.9%)




Table 2 illustrates the results ofthe binary multivariate logistic regression analysis.

Resultsof multivariate logistic regression analysis


Oddsratio(OR)

Significance(pvalue)

95%Confidence Interval (CI)

Primaryobjective

Episiotomy

0.037

<0.001

0.025-0.054

MaternalFactors

Ageof delivery

0.989

0.211

0.973-1.006


Parity

0.455

<0.001

0.387-0.537


Parity

0.455

0.387-0.537

Analgesiain labour

Entonox,Paracetamol, Codeine

4.899

0.943-25.455


Pethidine

3.237

0.151

0.651-16.102


Epidural

3.3

0.622-17.514

Assisteddelivery

Forceps

22.787

15.258-34.030


Vacuum

4.006

<0.001

2.959-5.421


Forcepsafter failed vacuum

1.848

1.149-2.973






Conclusions: The incidenceof OASIS in our obstetric unit is similar to the national data.Indeed, with 36,204 vaginal deliveries, we believe this is one of thelargest cohorts of consecutive women analysed for OASIS. The use ofepidural analgesia is not an independent risk factor for OASIS.Although the RCOG so far only recommends mediolateral episiotomiesduring instrumental deliveries, our study shows that mediolateralepisiotomy is protective [OR 0.037, p<0.001 (95% CI 0.025 -0.054)] even in spontaneous vaginal deliveries. Similar to previousstudies we found that the risk of OASIS was significantly increasedwhere assisted vaginal delivery took place. When instrumentaldelivery is indicated, obstetricians should aim for vacuum deliveryrather than forceps, as the risk of OASIS with forceps is almost sixfold greater.
References:

  1. BJOG2013;120:1516-25.

  2. RCOG. GTGNo. 29

  3. CochraneDatabase Syst Rev. 2011 Dec 7;(12):CD000331