(HealthDay News) – Narrow-angled episiotomies increase the risk of obstetric anal sphincter injuries (OASIS), while other factors, including point of incision and episiotomy length and depth, reduce the risk of OASIS.
Mona Stedenfeldt, of the University Hospital of North Norway in Tromsø, and colleagues conducted a case-control study of 74 women with a history of a single vaginal birth and an episiotomy. The researchers identified, photographed, and measured the episiotomy scar in 37 women with OASIS and 37 controls.
The researchers found that, for each 5.5mm increase in episiotomy depth there was a 70% decrease in the risk of sustaining OASIS (odds ratio [OR], 0.3); for each 4.5mm increase in the distance from the midline to the incision point of the episiotomy there was a 56% decreased risk (OR, 0.44); and for each 5.5mm increase in episiotomy length there was a 75% decrease in the risk of sustaining OASIS (OR, 0.25). The mean angle did not differ between the groups, but a “U-shaped” association was seen between angle and OASIS (OR, 2.09), with an angle either <15 degrees or >60 degrees associated with an increased risk (OR, 9.0).
“The present study showed that scarred episiotomies with depth >16mm, length >17mm, incision point >9mm lateral of midpoint and angle range 30–60 degrees are significantly associated with less risk of OASIS,” the authors write.