Diagnosis of Obstetric Anal Sphincter Injuries (OASIs) Using Transperineal Ultrasound Scan (TPUS)

Study Overview
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Brief Summary
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It is common for women to sustain perineal trauma following their first vaginal delivery. Sometimes these can extend to the anal sphincter, and these are referred to as Obstetric Anal Sphincter Injuries (OASIs). Occasionally OASIs may not be detected at delivery. If these tears are missed they would not be repaired and this may lead to incontinence of wind (flatus) or of faeces, both of which can have a significant impact on quality of life. The investigators would like to establish whether a 3D ultrasound scan probe placed outside the vagina can identify the anal sphincter defects and to investigate whether the use of TPUS immediately after primary repair of OASIs is an useful tool to minimise an inadequate repair. The investigators would also like to look at changes that occur to the pelvic floor muscles during labour and to identify injuries to the pelvic floor muscle (levator ani) by ultrasound. Such injury to pelvic floor muscle is associated with vaginal prolapse.

Detailed Description
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Following the first vaginal delivery 85% of women will sustain perineal trauma (1). Sometimes these can extend to the anal sphincter, and these are referred to as Obstetric Anal Sphincter Injuries (OASIs). Occasionally OASIs may not be detected at delivery. If these tears are missed they would not be repaired and this may lead to incontinence of wind (flatus) or of faeces, both of which can have a significant impact on quality of life. Endoanal ultrasound (where an ultrasound probe is inserted directly into the back passage) is the gold standard diagnostic tool to detect OASIs. It is however not available in most obstetric units. Transperineal ultrasound (where an ultrasound probe is placed on the perineum)(TPUS) in contrast is available in most obstetric units and therefore we wish to determine whether TPUS in addition to a routine clinical examination will increase the detection rate of OASIs. Anal incontinence can also occur if the anal sphincter are not repaired adequately. Therefore we want to investigate whether the use of TPUS immediately after primary repair of OASIs is an useful tool to minimise an inadequate repair. The other aim of the study is to look at changes that occur to the pelvic floor muscles during labour by ultrasound. It is known that certain muscle changes may lead to urinary incontinence and pelvic organ prolapse. However limited studies have evaluated the natural history of the pelvic floor muscles in labour. We therefore wish to perform a transperineal ultrasound each time the midwife or doctor caring for the woman in labour decides the woman in labour needs a vaginal examination. This will provide important information regarding changes that occur to the muscles of the pelvic floor during normal labour. References: 1)Byrd L,Hobbiss J,Tasker M. Is it possible to predict or prevent third degree tears? Colorectal Dis 2005;7:311-8.

Official Title
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Diagnosis of Obstetric Anal Sphincter Injuries (OASIs) Using Transperineal Ultrasound Scan (TPUS)

Conditions
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Obstetric Anal Sphincter Injury

Intervention / Treatment
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* Diagnostic Test: three dimensional Transperineal Ultrasound Scan


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: women who are undergoing their first vaginal delivery 37 weeks of gestation or more a singleton pregnancy cephalic presentation maternal age 18 years old or more and being able to read and understand English. Exclusion Criteria: Exclusion criteria are those who do not fit in the inclusion criteria.

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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Female

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Three dimensional transperineal ultrasound<br>This is a single arm study. All women who delivered vaginally will be included in the study . The planned interventions are: Clinical vaginal and rectal examination Three dimensional transperineal ultrasound. | Diagnostic Test: three dimensional Transperineal Ultrasound Scan<br>* Diagnostic test: three dimensional transperineal ultrasound scan<br>* Other names: TPUS;|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Diagnostic test accuracy of three dimensional and transperineal ultrasound (TPUS) for diagnosing Obstetric Anal Sphincter injurieS (OASIS) | To calculate the diagnostic test characteristics (e.g sensitivity, specificity, positive predictive value, negative predictive value) to enable comparison of 3D TPUS assessment with clinical examination findings of the anal sphincter following vaginal delivery | immediately Postpartum | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Prevalence of Levator Ani Muscle Injury in women who delivered vaginally and by caesarean section | To calculate the prevalence of levator ani muscle avulsion in women after caesarean section and vaginal delivery. | during first and second stage of labour, immediately Postpartum, 3 months Postpartum and 10-12 weeks Postpartum (in women who deliver vaginally) | 
| Levator ani muscle hiatus area (cm2) | Levator hiatal dimensions can be determined on three dimensional transperineal ultrasound by identifying the plane of minimal dimensions. | during first and second stage of labour, immediately Postpartum, 3 months Postpartum and 10-12 weeks Postpartum (in women who deliver vaginally) | 
| Fetal head position | Fetal head position is assessed by clinical examination and transabdominal ultrasound. The possible outcomes of both assessments are occiput anterior, occiput posterior or occiput transverse. | during first and second stage of labour | 
| Fetal head station assessed by clinical examination | Fetal head station is assessed by clinical examination. The fetal station is the relationship of the presenting part to the ischial spines. It is measured in centimetres above or below the ischial spines (+2,+1,0,-1 or -2). | during first and second stage of labour | 
| Fetal head station assessed by transperineal ultrasound | Transperineal ultrasound is used to assess fetal head station by measuring the angle of progression. Angle of progression is the angle between the longitudinal axis of the pubic bone and a line joining the lowest edge of the pubis to the fetal skull contour. | during first and second stage of labour |