Vaginal delivery after OASIS

Vaginal delivery after OASIS

Vaginal delivery after a previous injury to the anal sphincter muscles (OASIS) is generally considered safe. Previous OASIS is not considered an absolute contraindication to vaginal delivery, but there is an increased risk of recurrence of OASIS compared to women in repeated deliveries without previous injury. The decision regarding the mode of delivery should be individualized, incorporating the patient's preferences, details of previous deliveries, current pelvic floor symptoms, and the results of objective assessment tests (anorectal manometry and TRUS and/or TPUS) with an emphasis on shared decision-making with the patient.

The success rate of a vaginal delivery after OASIS is high, and most women who choose it, succeed in giving birth by vaginal delivery. The recurrence rates of OASIS according to recent literature range from 3.7%–13.4% in large groups, which is not very different from the rates of primary OASIS in the same populations. It is important to note that the rate of primary OASIS in Israel is approximately 10 times lower than reported in the literature, and from a few studies that examined the rate of recurrent OASIS in Israel, a rate of 2.4% was found, which is also lower than that described above.

Possible complications include recurrence of OASIS, long-term anal incontinence and fecal leakage (especially if recurrence occurs), and perineal pain.

Risk factors for recurrence include a large-for-gestational-age (LGA) infant, instrumental delivery, and a previous severe tear (fourth degree). The risk of long-term anal incontinence is higher in women with a previous severe injury, but the type of subsequent delivery (vaginal versus cesarean section) does not significantly change this risk. It is important to note that women with recurrent OASIS are more susceptible to long-term incontinence of gas and stool, which may impair their quality of life.

In conclusion, vaginal birth is generally safe and successful after a previous OASIS, but there is a slightly increased risk of recurrence and long-term pelvic floor dysfunction, particularly in those with a severe tear. Individualized counseling and risk assessment are essential.