Third degree perineal laceration during delivery, IIIa

This code signifies a severe obstetric injury involving a third-degree laceration of the perineum that occurred during childbirth. Specifically, it indicates a tear extending through the perineal skin, vaginal mucosa, and the external anal sphincter, but with less than 50% of the external anal sphincter thickness torn (IIIa).

Apply this code when documentation clearly states a third-degree perineal laceration occurred during delivery, and further specifies it as a IIIa tear. This diagnosis is typically made by the delivering clinician and documented in the delivery notes or operative report.

• Differentiate carefully between IIIa, IIIb, and IIIc lacerations based on the extent of external and internal anal sphincter involvement.
• Ensure the documentation explicitly states "during delivery" to support the use of an O70 code.
• Do not confuse with O70.1 (second-degree perineal laceration) or O70.3 (fourth-degree perineal laceration).