Hypothesis / aims of study
Obstetric anal sphincter injuries (OASIS) are associated with faecal incontinence, which impair women’s quality of life. Episiotomy is the commonest obstetric procedure during a delivery. There are efforts to reduce the episiotomy rate for women to reduce the morbidity of women. However, there is evidence showing that Asian women delivered in areas with a low episiotomy rate had a higher OASIS rates.
This study evaluated the incidence of OASIS in our unit while there was a reducing episiotomy rate throughout the last few years.
Study design, materials and methods
This was a retrospective study evaluating the incidence of OASIS from year 2015 to 2021. The electronic hospital delivery database was reviewed. The delivery record was entered into the electronic system in the delivery suite immediately after the delivery of women. Generally, normal vaginal delivery (NVD) was conducted by midwives. The use of episiotomy was up to the decision of operator at the time of delivery. Per-vaginal and per-rectal examination would be conducted to explore for OASIS after the delivery. If there were OASIS, obstetrician would confirm and repair it immediately; and the electronic operative record was completed right after the procedure.
Results
There were a total of 30,984 vaginal deliveries of singleton pregnancy. Among them, 28,499 (92%), 2,078 (6.7%) and 407 (1.3%) had NVD, ventous extraction and forceps delivery, respectively. In all, 50.3% and 49.7% were nulliparous and multiparous women. The episiotomy rate for nulliparous and multiparous women having NVD reduced from 90% to 54% and 30% to 19% from 2015 to 2021, respectively.
The OASIS rate for nulliparous NVD women with and without episiotomy ranged from 0.47% to 1.6% and 0.26% to 2.6% per year; while these were 0.15% to 1.6% and 0.1% to 0.4% for multiparous NVD women. There was no statistical significant difference in OASIS rate throughout the 7 years; except a lower OASIS rate in nulliparous women with no episiotomy. However, from 2017 to 2021, there was an increase in OASIS rate in nulliparous NVD women (Chi-square for trend, P=0.007). Among the OASIS, 67(38%), 88(49%), 13(7%) and 9(5%) were 3a, 3b, 3c and 4th degree perineal tears, respectively. There was one button hole tear (1%).
Interpretation of results
There was significant reduction of episiotomy rate in both nulliparous and multiparous women having normal vaginal delivery. However, there was no significant difference in rate of OASIS; except a lower OASIS rate in nulliparous women with no episiotomy.