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Why is OASIS important?
Obstetric anal sphincter injuries (OASIS) or 3rd/4th degree tears are a serious complication of childbirth that can lead to anal incontinence (AI). AI can have a devastating impact on a person’s quality of life and is perceived as a social stigma. Due to these childbirth related injuries, women are nine times more likely to develop AI compared to men.
How common is OASIS?
A recent RCOG commissioned review showed an incidence of 6% in first vaginal births in England.(l)
Can OASIS be repaired?
OASIS, if detected at childbirth, can be repaired. However, studies show that nearl one-third of women will go on to develop anal incontinence at a later age despite the repair. The diagnosis is also missed in some women during childbirth who go on to develop anal incontinence sooner than later.
Isn’t episiotomy dangerous? Why not just let the perineum tear?
The RCOG review of more than a million first vaginal births found that OASIS was 60% more common in nulliparous normal births without episiotomy (3.4%) compared to women given episiotomy (2.2%).
Women delivered by forceps in first vaginal births were 3.5 times more likely to have OASIS without episiotomy (22%) compared to with episiotomies (6%).
Women delivered by vacuum in first vaginal births were 3 times more likely to have OASIS without episiotomy (6.4%) compared to with episiotomies (2.3%).
Studies from Denmark, Australia and Netherlands also show episiotomies are safer.
What is the relationship between episiotomy angle & OASIS?
Studies with midline episiotomies from USA show an incidence of up to 20% OASIS. With mediolateral episiotomies, the incidence of OASIS depends on how close the episiotomy is angled is to the midline, hence the anal sphincter muscles.
Eogan[2l found the incidence was 10% if the post-delivery sutured episiotomy angle was< 25 degrees, and dramatically reduced to 0.5% if the angle was ~ 45 degrees. The incidence of OASIS reduced by 50% for every 6 degrees the episiotomy is away from the midline. However, if the episiotomy suture angle is >60 degrees, OASIS incidence rises .
To minimise the risk of OASIS, post-delivery sutured episiotomy angle of 40-60 degrees is the “SAFE-ZONE”.
How do I ensure an episiotomy angled in the SAFE-ZONE?
An incision angle of 60 degrees  is required to achieve a
post-delivery sutured episiotomy angle of 45 degrees. This is because there is significant perineal distension at crowning. Studies show this is the safest cutting angle for the episiotomy. Hence the RCOG recommendation to cut the episiotomy at 60 degrees[s].
Why use the EPISCISSORS-60™?
EPISCISSORS-60 have a unique patented form and design. They have a guide-limb that points towards the anus and is in the vertical plane. The scissor blades constantly maintain a 60 degree angle from the guide-limb. The flexible nature of the guide accommodates the spherical distension at crowning.
They have also been confirmed by NICE as being the only CE marked technology to achieve a 60 degree angle at cutting.
What is the evidence for EPISCISSORS-60™?
Four clinical studies have been done using the EPISCISSORS-60 showing episiotomy suture angles between 40-52 degrees [6-8]. The suture angle will depend on how distended the perineum is when the episiotomy is given. The more distended the perineum, the lesser the post-delivery angle.
Studies from 5 UK hospitals with 20,000 births have shown a 20-50% reduction in OASIS (Van Roon 2015, Ling Liing 2016)
What is the current practice?
The present practice of performing episiotomies is by ‘eyeballing’ the angle. The definition of ‘Eyeballing’ is to measure or weigh something without any tools.
How good are we at EYEBALLING?
Research studies have shown that doctors and midwives are unable to correctly estimate the angle at the time of birth. Andrews et al  found “No midwife and only 22% of doctors performed truly mediolateral episiotomies. It appears that the majority of episiotomies are not truly mediolateral but closer to the midline”. Mean angle by midwives was 20 degrees and by doctors was 27 degrees. Only 13% episiotomies were in the SAFETY ZONE (post-delivery angle ~40 degrees). Tincello et al [lO] asked doctors and midwives to draw their episiotomy on a validated pictorial questionnaire. Only 1/3rd episiotomies were ~40 degrees. When asked specifically to cut at 60 degrees, only 15%.