It is estimated that between 1-10% of vaginal births result in 3rd or 4th degree perineal tears. To learn more about the different grades of perineal tears click here. Understanding the risk factors and possible techniques for prevention of 3rd and 4th degree perineal tears, also known as obstetric anal sphincter injuries (OASIS), is incredibly important for improving maternal health outcomes after a vaginal delivery. 

OASIS negatively impact a mother’s quality of life and morbidity as obstetric sphincter damage is the most common cause of fecal incontinence in women (Dudding et al, 2008). Other complications following an OASIS include pelvic pain, greater risk for infections leading to increased antibiotic use following surgery, and require a longer healing time that could impact one’s ability to perform daily tasks, childcare, and return to physical activity or exercise. This is particularly relevant when working with athletes of all levels in the greater Boulder area who are looking to return to sport following childbirth. Physical therapy rehabilitation can significantly improve continence, reduce pain, and provide guidelines for healing or returning to sport. 

One study by Smith et al 2013, collected data in 2006 from 2,754 women who had given birth vaginally to a single baby in a variety of birthing locations including hospitals, midwifery led centers, and home births in South East England. The portion of women without perineal tears were 9% in first time mothers and 31% for second time mothers. Women who gave birth at home or in a midwife led center were slightly less likely to experience perineal injury.

Risk factors associated with a 3rd or 4th degree perineal tear were: 

• First vaginal delivery

• Use of forceps during delivery

• Longer duration of the seconds stage (pushing) of labor

• Heavier infant birth weight

Prevention of OASIS is an important part of maternal health. A Cochrane Review from 2017 reports that there is moderate quality evidence that the use of warm perineal compress and perineal massage during delivery may reduce the incidence of 3rd and 4th degree perineal tears. The incidence of OASIS in Norway decreased from 4% to 1% in 2007. The change was attributed to an intervention program to slow the delivery of the infant’s head by instructing the mother not to push at that time (Hals E et al. 2010). Overall further research should be conducted to better understand ways to prevent obstetric sphincter injuries.

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