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  • Writer's pictureKaren Crudden


OASIS.....Obstetric anal sphincter injuries

3rd and 4th degree tears of the perineum are know as OASIS

3rd degree tears are split into 3 subgroups

3a: Less than 50% of external anal sphincter (EAS) thickness torn

3b: More than 50% of EAS thickness torn

3c: Both EAS and internal anal sphincter (IAS) torn

4th degree tear: Injury to perineum involving the anal sphincter complex (EAS and IAS) and anal epithelium

The incidence of OASIS is 6.1% in first time births

Risk factors for OASIS

  • Asian ethnicity

  • First vaginal birth (including is previous c-section)

  • Birthweight >4kg

  • OP position

  • Instrumental birth

  • Shoulder dystocia

  • Prolonged push PHASE/ 2nd stage

  • Midline episiotomy

  • Previous OASIS

Risk reduction strategies during birth

Perineal warm compresses

Perineal massage

Birth in positions that reduce pelvic floor trauma- side lying, 4 point/all fours, kneeling or standing

Controlled birth/hands on approach

Consider vacuum prior forceps

Episiotomy with forceps

Unfortunately OASIS can occur but know it was never any you did wrong. Bowel issues post repair are reducing due to excellent surgical repairs and early physio management these days. Here are some tips to help you in those early days

-Take your pain medication and ant- inflammatories it will literally be a pain in the butt

- Ice packs or gel pads for 10-20min intervals for 24-72 hours

- Stool softeners for minimum 10 days after,

- laxatives to help reduce pain with that first bowel motion

- 2-3L of fluid per day and ‘wet’ foods (sups/stews, veg, salads, kiwis, pears, berries) to keep stool formed but soft

- Side lying for breastfeeding to ease pressure of butt

- Pace activities throughout the day especially ones that involve long periods of standing, and squatting..... NO high impact!

- Check and clean the wound daily – get your midwife to go through this with you, they do this day in day out, no biggie

- No intercourse for first 8 weeks minimum then lube x 100 (water base if using condoms/ oil based if not)

I highly recommend a pelvic health physiotherapy assessment from 6 weeks, even if you have no symptoms. This is to rebuild the pelvic floor and surrounding muscles and extend on all the above tips and more to prevent symptoms from occurring during exercise, future pregnancies or menopause.

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