Objective: This study is aimed at establishing local data on the incidence of obstetric anal sphincter injuries (OASIS) (third and fourth-degree perineal tears), risk factors of OASIS and to compare the results with international data.

Methodology: It is a retrospective review and analysis of women with OASIS in the Department of Obstetrics and Gynaecology, Ampang Hospital (AH) from 2014 – 2016. The cases were identified through maternity records. The international data on OASIS was obtained through web-database search. The data was collected and statistically analysed using SPSS.

Results: We reviewed 29,289 deliveries, over the 3-year-period. There were 42 cases of OASIS, giving an incidence of 0.16%, which was very low as compared to international data, which ranged from 0.6-4.2% (p<0.001). Greater birth weight and instrumental delivery are recognized risk factors of OASIS. However, the protective effect of episiotomy is conflicting. We studied these risk factors in AH and compared them with international data. We found that the mean birth weight in AH was lower, at 3.101 kg, as compared to 3.389 kg and 3.352 kg in the UK and USA respectively. The rate of instrumental delivery in AH was low, at 3%, as compared to 10-13% and up to 23% in the UK and USA respectively (p<0.001). There was also an exceptionally high rate of episiotomy in AH, at 63.16%, as compared to 15% and 11.6% in the UK and USA respectively (p< 0.001).

Conclusion: The low incidence of OASIS in AH could be associated with lower mean birth weight, lower rate of instrumental delivery and higher rate of episiotomy.