Introduction
For women undergoing a vaginal birth an estimated 60-70% will sustain perineal trauma that requires suturing1. However, for some women tears will extend into the anal muscle and are called obstetric anal sphincter injuries (OASIS). These tears are further classified depending on the extent of the injury. A third degree OASIS is defined as a partial or complete disruption of the anal sphincter muscle and it can affect the external sphincter, internal sphincter or both and a fourth degree OASIS is defined as complete disruption of both sphincters and anal epithelium or rectal mucosa. OASIS is reported to occur in 0.6%-9.0% of vaginal deliveries1. They are recognised to be a major risk factor of anal incontinence in childbearing women2 however, despite the known morbidity there is limited data on the long term consequences including subsequent birth and its mode on bowel function and quality of life (QoL). Most women with a previous OASIS have no bowel problems and, when no sphincter defect is seen on ultrasound, the decision to pursue a vaginal birth is reasonable. Although this is becoming more accepted and wanted by women, information concerning the impact of this management on their bowel symptoms at the long term and the quality of life both prior and following subsequent birth, either vaginal or caesarean section, is lacking. Evidence is required before the practice of promoting a particular mode of delivery for women with previous OASIS that is considered optimal becomes routine.
Objective
To investigate the impact of a subsequent birth and it’s mode on bowel function and Quality of Life (QoL) in women with a previous OASIS.
Methods
The research was funded by the NIHR Clinical Doctoral Research Fellowshiop and undertaken at Birmingham Women’s & Children’s NHS Foundation Trust (BWCNFT), where, as Specialist Perineal Midwife, I hold two dedicated OASIS clinics to review women who sustain OASIS and perform endoanal ultrasound scans (EAUS) to identify anal sphincter abnormalities; a postnatal clinic for review of women at three months following OASIS and an antenatal clinic for review of women with a previous OASIS presenting in a subsequent pregnancy. The PhD consisted of the following three linked studies:
1. A systematic review and meta-analysis of the available published literature regarding the impact of mode of subsequent birth on bowel symptoms and/or QoL for women with previous OASIS.
2. A postal questionnaire-based follow up study of 294 women who had previously attended either of the two OASIS clinics to assess longer term bowel function and QoL.
3. A prospective cohort study of 175 women with previous OASIS reviewed prior to and following the subsequent birth to determine the impact on bowel function and QoL of a subsequent birth and its mode.
A validated bowel symptom and QoL self-completed questionnaire was used in studies two and three to capture this data3.
Results
This is the first systematic review on impact of subsequent birth and its mode on AI and/or QoL for women with previous OASIS4. As no RCTs were identified, this is based on data from 27 cohort and case control NRSs, across nine countries, predominantly with methodological inadequacies. Due to the poor methodological quality and overall heterogeneity of included studies it is not possible to determine the optimal mode of subsequent births for women with previous OASIS and therefore better data are needed. In the absence of higher quality evidence this systematic review and meta-analysis would support current recommendation of a subsequent vaginal birth for women with previous OASIS who demonstrate no AI symptoms or sphincter defects. The postal questionnaire-based follow up study and the prospective cohort study both add considerably to the limited data that is currently available on the long term impact, including subsequent birth and its mode, on both bowel function and QoL for women with a previous OASIS. Firstly, both of these studies have demonstrated the relationship of short term bowel symptoms and identification of maternal, neonatal and birth related characteristics that predictors of longer term outcomes. Also highlighting the importance of specialist review both postnatally following OASIS and antenatally prior to a subsequent birth to accurately record the presence of any bowel symptoms. Secondly, through this cohort study that satisfied all of the methodological and quality standards found lacking in currently available studies, for women with previous OASIS who have no bowel symptoms and/or known defects in the anal sphincter muscle, a decision to pursue a subsequent vaginal birth appears sensible.
Conclusion and contribution to practice/research
In the absence of higher quality evidence my comprehensive studies provide reassurance for clinicians to support, and for women with a previous OASIS who have normal bowel function and have no anal sphincter abnormalities to pursue, a subsequent vaginal birth. This serves to potentially reduce the number of women with previous OASIS undergoing an elective caesarean section, which will have patient benefits of a reduction in associated morbidities and NHS cost benefits. The findings from my work also highlight the need for future studies to investigate the most suitable mode of subsequent birth for women with previous OASIS who have abnormal bowel function and/or abnormal EAUS. Such studies will present challenges for recruitment as women with bowel symptoms and/or abnormal EAUS may be reluctant to pursue a vaginal birth when the implications of worsening of bowel symptoms and/or further damage to the anal sphincter may occur. Therefore, to ensure timely conclusion and reach the necessary power to address important outcomes it is likely that such research will need to be multi-centre/international.
1. RCOG. Third- and Fourth-degree Perineal Tears, Management (Green-top 29). RCOG Greentop Guidleines. 2015(2).
2. Thiagamoorthy et al. National audit to assess the true incidence of perineal trauma and its subsequent management in the United Kingdom. BJOG. 2013;120:478-9.
3. Bugg GJ KE, Hosker G A new condition-specific health-related quality of life questionnaire for the assessment of women with anal incontinence. BJOG. 2001;108:1057-67.
4. Webb SS, et al . Impact of subsequent birth and delivery mode for women with previous OASIS: systematic review and meta-analysis. IUJ. 2016:1-8.
Publications from the BASIQ Study
The impact of subsequent birth and delivery mode for women with previous OASIS: systematic review and meta-analysis. Sara S Webb, Margarita Manresa, Derick Yates, Matthew Parsons, Christine MacArthur, Khaled M Ismail. Int Urogynecol J (2016) doi: 10.1007/s00192-016-3226-y