OBJECTIVE:

To analyze the associated risk factors of obstetric anal sphincter injury in a population in which the use of forceps is well accepted.

MATERIALS AND METHODS:

A simple retrospective cohort was performed where all women with vaginal delivery were identified in a period of 5 years (January 2013 to December 2017). Pregnancies older than 35 weeks were included, unique and in cephalic presentation. The dependent variable of obstetric lesion of the anal sphincter was classified in 3rd and 4th grade. The SPSS 23 program was used for the statistical analysis. χ2 test and Student's t test were used to compare the groups, as well as Odds radio (OR) with a 95% confidence interval (95%CI).

RESULTS:

A total of 6199 women were included. The average age was 26.5 years, birth weight of 2745 grams on average, forceps were placed in 6.9% (n = 428). The frequency of obstetric lesion of the anal sphincter was 1.03% (n = 65) in the study period. The following risk factors were found to be associated with anal sphincter injury: use of forceps OR 22.4 (95% CI 13.3-36.7, p <0.001), primiparity OR 2.8 (95% CI 1.68-4.93 p < 0.001.

CONCLUSIONS:

Maternal age of 20 to 30 years, fetal weight greater than 3500 grams, births with forceps and primiparity are risk factors for obstetric anal sphincter injuries.

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