An obstetric sphincter injury risk identification system (OSIRIS): is this a clinically useful tool?

INTRODUCTION AND HYPOTHESIS: To establish the contribution of maternal, fetal and intrapartum factors to the risk of incidence of obstetric anal sphincter injuries (OASIS) and assess the feasibility of an OASIS risk prediction model based on variables available to clinicians prior to birth. METHODS: This was a population-based, retrospective cohort study using single-site data from the birth database of Aarhus University Hospital, Denmark. The participants were all women who had a singleton vaginal birth during the period 1989 to 2006. Univariate and multivariate logistic regression analyses were performed using multiple imputations for missing data and internally validated using bootstrap methods. The main outcome measures were the contributions of maternal, fetal and intrapartum events to the incidence of OASIS. RESULTS: A total of 71,469 women met the inclusion criteria, of whom 1,754 (2.45 %) sustained OASIS. In the multivariate analysis of variables known prior to birth, maternal age 20 - 30 years (OR 1.65, 95 % CI 1.44 - 1.89) and ≥30 years (OR 1.60, 95 % CI 1.39 - 1.85), occipitoposterior fetal position (OR 1.34, 95 % CI 1.06 - 1.70), induction/augmentation of labour (OR 1.46, 95 % CI 1.32 - 1.62), and suspected macrosomia (OR 2.20, 95 % CI 1.97 - 2.45) were independent significant predictors of OASIS, with increasing parity conferring a significant protective effect. The 'prebirth variable' model showed a 95 % sensitivity and a 24 % specificity in predicting OASIS with 1 % probability, and a 3 % sensitivity and a 99 % specificity in predicting OASIS with a 10 % probability. CONCLUSIONS: Our model identified several significant OASIS risk factors that are known prior to actual birth. The prognostic model shows potential for ruling out OASIS (high sensitivity with a low risk cut-off value), but is not useful for ruling in the event.

Coccygeal movement test: an objective, non-invasive test for localization of the pelvic floor muscles in healthy women.

OBJECTIVE: To evaluate the use of palpation of the coccyx (the coccygeal movement test, CMT) as a possible objective screening tool for the assessment of adequate localization of the pelvic floor muscles (PFMs). SUBJECTS AND METHODS: Twenty-four healthy female volunteers, known to be able to locate their PFMs, were given instructions (allocated at random) to perform a 'correct contraction', 'straining' or 'nothing' when examined by six independent assessors using the CMT. The assessors were blinded to the instructions and to the test results recorded by other assessors. Data were available for 137 observations, and these were dichotomized into either 'able to contract' ('correct contraction') or 'not able to contract' ('straining' or 'nothing'). This information was used to calculate the sensitivity, specificity and positive and negative predictive values for the CMT. RESULTS: The CMT correctly identified 56/58 observations when women did not perform the contraction of the PFMs compared to 61/79 observations when they did. Hence, the sensitivity and specificity were 97 and 77%, respectively. CONCLUSION: This study showed that the CMT was a useful test to identify women who were able to localize their PFMs compared to those who were not, making it a potentially useful initial screening test in structured training programmes for the PFMs.