Obstetric anal sphincter injury (OASI), or severe perineal tears during vaginal birth, can lead to later pelvic floor problems.Cesarean delivery is the only known way to prevent this, but it was unclear which groups carried most risk for tears.Operative delivery, Asian race, and certain maternal conditions were linked to increased OASI risk.
Certain clinical and demographic factors were associated with higher rates of obstetric anal sphincter injury (OASI) among first-time mothers during vaginal birth, a large cohort study found.
In a study of more than half a million previously nulliparous women giving birth in California, OASI occurred in 4.4% with operative delivery being the strongest risk factor, reported Christina Chambers, PhD, of the University of California San Diego, and colleagues.
OASI occurred in 20% of forceps-assisted deliveries (adjusted relative risk [aRR] 4.38, 95% CI 4.11-4.68) and 12.3% of vacuum-assisted deliveries (aRR 2.95, 95% CI 2.86-3.04), compared to just 3.5% of nonoperative vaginal deliveries, they wrote in JAMA Network Open.
Demographics also affected the OASI risk estimates. Compared to non-Hispanic white women, those of Asian ancestry showed nearly doubled risk (aRR 1.92, 95% CI 1.86-1.99) while Black and Hispanic women both had lower risk of OASI.
