Preventing Tearing in Birth: OSAI

thefitpelvis
Jun 4
2 min read

When preparing for birth, there’s so much focus on the baby — but your pelvic floor deserves attention too. One topic that doesn’t get talked about enough is OASI — Obstetric Anal Sphincter Injury. This is also called a 3rd or 4th degree tear. These tears are less common than 1st and 2nd degree tears and have a bigger impact on lifelong health and bowel function. 1st and 2nd degree tears typically heal well without lifelong symptoms.

As pelvic health physical therapists, our goal is to help you understand your risk and take proactive steps to protect your body during delivery.

Let’s dive into what OASI is, why it matters, and what you can do to lower your risk.

Who’s at Higher Risk?

Certain factors increase the likelihood of OASI, including:

First vaginal delivery or subsequent births with a previous OASI.
Instrumental delivery (forceps or vacuum) increases the risk of OASI to 3.5%. This means 3.5 of 100 births with forceps will have OASI.
Shoulder Dystocia increases the risk of OASI because the baby’s shoulders get stuck behind the pelvic bones.
- Large babies increase the risk of shoulder dystocia. If the baby is larger than 9lbs 14 oz the risk of shoulder dystocia increases to 20-50% from 9-14%.
Prolonged pushing phase of labor greater than 109 minutes increases OASI likelihood.
Midline episiotomy is harmful because it weakens the tissue and the tear is likely to continue at the end of the episiotomy. A lateral episiotomy is beneficial to avoid the anal sphincter.
Perineal body length that is less than 3 cm increases to 40% risk of OASI vs 5% risk if the length is greater than 3 cm. That risk continues to decrease for every ½ centimeter past longer than 3 cm.

BUT: Even with risk factors, there are strategies you can use to help protect your pelvic floor during delivery!

How You Can Help Prevent OASI

Working with a pelvic health PT to determine your specific risk factors and reduce the risks that are modifiable. The modifiable factors are the ones that can be changed including perineal body length (indicator of pelvic floor tension), labor pushing time and ability of the baby to get into optimal position and move smoothly through the birth canal.

While no one can guarantee that an OASI won't happen, education + preparation + teamwork with your providers = real power and ability to make the best decisions for you.

Caring for your pelvic floor during pregnancy isn’t just about preventing problems — it’s about setting yourself up for a stronger, smoother recovery, no matter how birth unfolds.

Your body is wise, strong, and deserves all the support it can get.

Want to learn more about perineal massage and birthing breathwork?

Call/text 214-600-8168 to join a birth prep course where we cover pushing techniques, whole body exercises and pelvic floor relaxation.