Obstetric anal sphincter injuries (OASIS) are the leading cause of incontinence fecal in women, in addition to causing other disabling consequences in the short and long term.Recent studies suggest that maternal ethnicity may play a role in the risk of suffer them. A large proportion of the women who give birth at Hospital del Mar are of the Indian subcontinent, so we believe it is relevant to study whether these are at greater risk of suffering tears during vaginal delivery.
 A relevant proportion of the women who give birth at the Hospital del Mar, approximately 20% are from countries of the Indian subcontinent such as Pakistan, India,Nepal or Bangladesh.

The main objective is to investigate whether women from the Indian subcontinent (India, Pakistan, Bangladesh) are at increased risk of anal sphincter tears (anal sphincter tearsperineal types III and IV) during vaginal delivery.Likewise, secondary objectives are to study the role that the type ofdelivery, maternal age, health care after delivery, episiotomy, fetal weight, parity and type of anesthesia to identify risk factors for this condition.

This is a retrospective analytical observational case-control study. Hospital studies performed in the Department of Gynecology and Obstetrics of the Hospital del Mar, in Barcelona. This study was approved by the clinical research ethics committee from IMIM on 01/12/2022 with file number: 2021/10116.
Data has been collected on all deliveries carried out at the Hospital del Mar between 01January 2017 and January 1, 2021. Cesarean sections, fetal deaths and legal terminations of pregnancy, multiple pregnancies and losses due to pregnancy deficiencyinformation, leaving a total of 3999 women for data analysis (see diagram flow of Fig. 1).
Among these, patients with obstetric injury to the anal sphincter have been selected (n=66,type III and IV perineal tears), which constitute the group of cases, which was compared withthe control group of patients without OASI (n=3933, without tear or type I and II tears). The Information was collected retrospectively through the birth book and clinical history. Computerized in the IMASIS system of the Hospital del Mar.
The main dependent variable studied is maternal ethnicity. The country of origin was recorded in the birth book by the doctor or midwife who attended to the patient, in case In the absence of this data, other documents from the computerized HC were searched. It has been classified ethnicity into different groups taking into account a set of factors sociocultural and geographical: Indian subcontinent, North Africa and the Middle East, Africa sub-Saharan, Latin America, East Asia and Caucasian ethnicity.

The outcome of the study was defined by the Odds Ratio, which determined whether the variousvariables are a risk factor for suffering an obstetric injury to the anal sphincter. For the statistical analysis, the IBM SPSS package version 29.0 for MacOS was used. Descriptive statistics were performed on the included patients (n=3999). The test of Hypothesis contrast used were Chi-Square (X2) or Fisher's exact test, depending on the theoretical total number, for the analysis of the qualitative variables (categorical) and the Mann-Whitney U test for non-quantitative variables. Parametric (maternal age) since they did not follow a normal distribution, which was determined by the Kolmogorov-Smirnov test.
A first univariate analysis was performed using logistic regression. Subsequently it has been carried out a multivariable logistic regression with the significant variables in the first analysis to adjust for interactions and possible sources of confusion. In all the cases a statistical significance level of 0.05 has been defined and the confidence interval It has been calculated with an accuracy of 95%.

During the period studied, a total of 5411 births were attended in our center, of which 3999 were vaginal. The average age of our population was 30.8 years, with a standard deviation of 6.04 years, the minimum age was 15 and the maximum age was 47. 
The majority of the patients studied (49%) were Caucasian, followed by those fromIndian subcontinent (22%) and Latin America (15%).  The women ofIndian subcontinent had the lowest percentage of children weighing more than 3500g and those that presented less nulliparity. The characteristics of the patients of bothgroups are shown in table 1
Among these, 66 OASIS were diagnosed, with a prevalence of 1.22% for the total of deliveries and 1.65% for vaginal deliveries. Of these OASIS, 53.03% were type IIIA, the36.36% type IIIB, 7.60% IIIC and 3.00% type IV, all women with OASI type IV from the Indian subcontinent.
The majority of women were primiparous (43.2%) and used epidural analgesia for childbirth (77%). Most had a non-instrumented delivery (87.3%). between births instrumented, the most frequent was the use of forceps, accounting for 9.8% of the total vaginal births. .
The characteristics of the women by ethnicity are described in Table 2. The univariate analysis showed statistical significance for age (OR 0.95 (0.91-0.99), p 0.014), instrumented delivery with forceps (OR 9.28 (5.59-15.39), p <0.001),primiparity (3.31 (1.93-5.67), p <0.001), episiotomy (OR 3.04 (1.87-4.95), p < 0.001) and Indian subcontinent ethnicity (OR 2.41 (1.46-3.95), p < 0.001). there was not statistically significant differences for the rest of the variables.
In the multivariate analysis  it was carried out with the significant variables for theunivariate analysis. Age and episiotomy lost statistical significance. The  remains statistically significant for primiparity with OR 3.56 (1.58-8.04, p 0.002), forceps delivery OR 13.70 (4.3942.80, p<0.001) and subcontinental ethnicityIndian OR 2.97 (1.48-5.97, p 0.002) for the presentation of OASIS in a vaginal delivery. The final multivariate model with these variables explains the association by 98.6%.

In our center the prevalence of OASIS was 1.65% for all vaginal deliveries. Similar to other observational studies carried out in Spain and France. It is less tan that notified by the Ministry of Health in 2015, which was 2.4%, although it must considered to be an underdiagnosed pathology.
The literature consulted indicates Asian ethnicity as a possible risk factor for OASI, specifically the south, southeast and Pacific islands had an increased risk of OASIS. The results of our study corresponded with previous findings and it was determined that women from India, Pakistan, Nepal and Bangladesh (subcontinent Indian) have significantly twice the risk of OASI than women fromother ethnicities represented (mostly Caucasian).
The main limitations of our study derive from its retrospective nature. For on the other hand, we have not been able to control the collection of information, so there is data that we have not obtained what we would have been interested in studying, such as the fetal position in thetime of birth or head circumference. Our low rate of OASIS.

Our study confirms that women from the Indian subcontinent have significantly increased risk of suffering an anal sphincter tear. Besides, the primiparity and instrumental delivery are also independent risk factors for suffer an OASI.

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