At operative birth, the type of episiotomy matters more than whether you cut

Design

Secondary analysis of a prospective multicentre cohort

Population

5,277 term singleton operative vaginal deliveries, US MFMU APEX cohort

Primary outcome

Third- or fourth-degree perineal laceration

Effect

Any episiotomy aOR 1.45 (95% CI 1.25 to 1.67); midline linked to more and mediolateral to less injury in key subgroups

This secondary analysis of the US MFMU APEX cohort examined 5,277 term, cephalic, singleton operative vaginal deliveries: 3,453 by vacuum and 1,824 by forceps. Episiotomy was done in 32.3%, mostly midline (1,301) and less often mediolateral (384). Obstetric anal sphincter injury occurred in 20.1%.

Overall, episiotomy was associated with higher odds of sphincter injury (adjusted OR 1.45, 95% CI 1.25 to 1.67). But the association reversed depending on the cut. Midline episiotomy during vacuum delivery was associated with more sphincter injury whether or not the woman had given birth vaginally before. Mediolateral episiotomy was associated with less sphincter injury in women without a previous vaginal birth, for both vacuum and forceps.

This is observational, the mediolateral group was small, and episiotomy was not randomly assigned, so the result cannot say a mediolateral cut prevents injury. It does fit earlier studies from other settings, and it argues against a midline cut at instrumental delivery. Where mediolateral is already the usual cut, the message is to keep the angle wide enough and avoid cuts that drift toward the midline.

• Think twice before a midline episiotomy at vacuum delivery; it was linked to more sphincter injury.
• If an episiotomy is needed at instrumental birth, consider mediolateral, especially for a woman without a previous vaginal birth.
• Aim the cut well away from the midline: a cut that ends up close to vertical behaves more like a midline one.
• Expect about one in five operative births in this cohort to carry a sphincter injury, and examine accordingly.
• Record the episiotomy type and angle in the delivery notes.

Why it matters

Pooling all episiotomies together hides opposite associations: one cut is linked to more sphincter injury and the other to less.

Don't overread it

This is observational; it shows association, not that a mediolateral cut prevents injury, and it does not support routine episiotomy.

The statistics, in plain English

An adjusted odds ratio of 1.45 means about 45% higher odds of injury with any episiotomy after accounting for second-stage length, age, BMI and birth weight. The interaction tests say this average hides different directions for midline and mediolateral cuts, but the mediolateral subgroup (384 women) is small and unmeasured factors in who got cut remain possible.

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