Obstetric Anal Sphincter Injuries – Maternal, Foetal and Sociodemographic Risk Factors: A Retrospective Register-Based Study

Objective. To determine risk and protective factors of obstetric anal sphincter injuries (OASIS). Design. A retrospective register-based observational study. Setting. Sweden. Population. A cohort of 988, 988 singleton term deliveries 2005-2016 were included. Methods. Data from the Swedish Medical Birth Registry and Statistics Sweden were extracted to identify cases of OASIS and maternal and foetal characteristics. Modified Poisson Regression analyses were performed to assess risk factors. Main outcome measures. Risk ratios for OASIS with 95% confidence interval associated with maternal and foetal risk factors were calculated. Results. The rate of OASIS was 3.5% (n=34, 583). Primiparity (aRR 3.13 95% CI 3.05–3.21), vacuum extraction (aRR 2.79 95% CI 2.73–2.86), forceps (aRR 4.27 95% CI 3.86–4.72) and high birth weight (aRR 2.61 95% CI 2.50–2.72) were associated with a significantly increased risk of OASIS. Increasing maternal age and decreasing maternal height increased the risk of OASIS. Smoking (aRR 0.74 95% CI 0.70–0.79) and low maternal education (aRR 0.87 95% CI 0.83–0.92) were associated with a decreased frequency of reported OASIS. Obesity decreased the risk of OASIS (aRR 0.90 95% CI 0.87–0.94), but only after adjusting for foetal birth weight. Previous caesarean section increased the risk of OASIS (aRR 1.41; 95% CI 1.36–1.47). Conclusion. Primiparity, instrumental delivery and high birth weight increased the risk of OASIS. Risk factors including BMI, height, age, smoking, maternal education, ethnicity and previous caesarean section also contribute to the overall risk of OASIS. Keywords. Obstetric sphincter injuries, risk factors, pregnancy.

Can transperineal ultrasound improve the diagnosis of obstetric anal sphincter injuries?

Background: Women with missed Obstetric anal sphincter injuries (OASIs) are at an increased risk of anal incontinence. Objective: To assess the accuracy of 3D Transperineal Ultrasound (TPUS) compared with clinical examination for detecting OASIs. Design: Prospective Observational longitudinal cohort study. Setting: District General Hospital, UK. Population or sample: Women undergoing their first vaginal delivery immediately postpartum. Methods: Perineal trauma was initially assessed by accouchers and women were then re-examined by a trained research fellow. A 3D TPUS was performed immediately after delivery before suturing to look for OASIs. Main outcome measures: OASIs on clinical examination and on TPUS Main Results: Two hundred and sixty-four women participated and two hundred and twenty-six (86%) delivered vaginally. Twenty-one (9%) sustained OASIs. Six (29%) of these tears were missed by the accoucher but were identified by the trained research fellow. TPUS identified 19 of the 21 (90.5%) OASIs. One percent (n = 2) had sonographic appearances of an anal sphincter defect and were not seen clinically. The positive and negative predictive of TPUS to detect OASIs were 91% and 99% respectively. TPUS identified 91% of OASIs compared to 71% detected by the accoucher. However, this was not statistically significant. Conclusions: More OASIs were identified on TPUS compared to examination. TPUS may have role in improving the detection rate of OASIs. Considering immense training and financial implications of using TPUS, attention needs to be focused on training to accurately identify anal sphincter defects on clinical examination. Funding:none Keywords: transperineal ultrasound imaging, obstetric anal sphincter injury

Diagnosis and Treatment of Obstetric Anal Sphincter Injuries: New Evidence and Perspectives

Perineal injury during childbirth is a common event with important morbidity associated in particular with third-and-fourth degree perineal tears (also referred to as obstetric anal sphincter injuries—OASIS). Early diagnosis of these damages is mandatory to define a prompt therapeutic strategy and thus avoid the development of late-onset consequences, such as faecal incontinence. For this purpose, various diagnostic exams can be performed after a thorough clinical examination. The management of OASIS includes several measures and should be individualized according to the timing and features of the clinical presentation.