Stages of Life > Pregnancy and Postpartum Life > Complications

We Need to Talk About OASIS Risk for Pregnant Women

Obstetric anal sphincter injuries are a rare but serious complication of vaginal delivery.

A doctor talks to a pregnant woman about OASIS risk.

Childbirth poses numerous risks to pregnant women, sometimes leading to long-term or permanent complications. But while some of these complications are common knowledge among medical professionals and patients, others, such as obstetric anal sphincter injuries (OASIS or OASI), are not as well known.

Obstetric anal sphincter injuries are a type of pregnancy complication that can occur during vaginal delivery. These injuries are also known as third- or fourth-degree perineal tears or lacerations. The perineum is the area between the anus and the vagina. The injuries involve the anal sphincter complex and even the anal mucosa in more extreme cases, explained Kecia Gaither, M.D., director of perinatal services/maternal fetal medicine at NYC Health + Hospitals/Lincoln in the Bronx, New York.

Injury to the anal sphincter is the most common cause of anal incontinence in otherwise healthy women, according to a 2015 article published in the Journal of Obstetrics and Gynaecology Canada.

These injuries occur in about 5.7 percent of women who are giving birth for the first time via vaginal delivery, and up to 1.5 percent of women giving birth subsequent times who do not have a history of OASIS, according to a 2021 article in the Journal of Clinical Medicine.

OASIS can lead to several short-term complications, including perineal pain and slower healing of surgical wounds. More severe cases pose a risk of long-term loss of bowel control in some patients.

Symptoms of OASIS

People who sustain an obstetric anal sphincter injury during childbirth may experience several symptoms.

According to Sean Ormond, M.D., an anesthesiologist in Arizona, these are warning signs that a woman may have OASIS:

Pain in varying degrees, depending on the severity of the tear
Fecal or urinary incontinence which may require wearing adult diapers until the issue is resolved
Sexual dysfunction or a general disinterest in sexual activity
Dyspareunia (painful intercourse) or persistent pain within the genital area
Internal or external hemorrhoids
Pelvic organ prolapse
Vesicovaginal fistulas, referred to colloquially as anal buttonholes, in which gas and feces are passed through the vagina rather than the anus due to the severity of the injury

If not addressed as soon as possible, these symptoms may have a lasting impact on the reproductive and digestive health of the woman. Such injuries can also cause emotional distress and lingering anxiety in the postpartum period.

Risk factors for OASIS

It is difficult to determine which mothers may end up with OASIS, or worse, an anal buttonhole. However, studies have verified these risk factors for OASIS in women:

First-time mothers
Women with a history of OASIS
Advanced maternal age
Births of large babies weighing more than the average of 9 pounds, 11 ounces
Epidural use
Induced labor
Extended labor period
The use of forceps or other implements

Should doctors warn patients about OASIS?

Physicians have mixed opinions on whether more patients should be warned about the possibility of this rare childbirth injury.

Some doctors acknowledge the importance of telling mothers about OASIS, especially if they are dealing with patients who are about to give birth for the first time vaginally.

"Doctors should warn more mothers, especially if they lie in the higher-risk groups and when they notice any risk factors," Ormond said.

However, while it is great to understand everything that could possibly go wrong at the time of your delivery, some doctors don't feel it's necessary to talk about OASIS before delivery.

"I don't believe that it is very important for all physicians to talk about OASI prior to delivery," said Greg Marchand, M.D., an OB-GYN in Mesa, Arizona.

"Even in cases where OASI occurs and the mother requires surgical correction, this surgery is minor compared to a cesarean section, which requires a large incision into the abdominal cavity," Marchand continued. "Adding to this, no obstetrician wants an OASI to occur, so it stands to reason they will do everything they can to prevent it. Therefore, there's not much use to discussing this rare complication prior to delivery."

However, he said anyone in high-risk groups should be advised of the risk of developing third- or fourth-degree perineal tears during the birthing process.

OASIS treatment

When a patient has an obstetric anal sphincter injury, a doctor initially assesses the extent of the injury. After that, surgery is always mandated for the condition and is done under a general anesthetic. Marchand explained that the anal sphincter needs to be sewn back together for the patient to control their stools properly and prevent fecal incontinence.

"This is not a difficult procedure but should be performed by someone with experience in this field. If performed incorrectly, the sutures may fail and the sphincter may not function properly," Marchand warned. "If not performed correctly at the time of delivery, you could need another surgery later to fix the damage. The appearance of this injury is often described as 'dovetailing' when the interrupted anal sphincter creates a shape similar to a bird's tail in the area of the anus."

Postsurgery, the attending physician prescribes antibiotics to prevent infection, as well as laxatives to prevent constipation and subsequent straining on the toilet, which could reopen the sutured areas.

Final word

While not all doctors consider it essential to warn pregnant women of OASIS risk before delivery, health literacy provides crucial support to women. Women need to be fully informed of the risks of perineal trauma, based on their individual expectations, needs and circumstances.

If you have recently given birth and notice any symptoms of OASIS, consult your physician immediately.