What maternal risk is increased with the sequential use of vacuum and forceps delivery?

The sequential use of vacuum and forceps delivery can significantly increase the risk of obstetric anal sphincter injury (OASIS). This condition includes third- and fourth-degree perineal lacerations, which can occur due to the combined forces applied during these assisted delivery techniques.

In using both vacuum and forceps, the risk of traumatic delivery is heightened, as each device exerts different levels of force and traction on the fetal head and perineum. This increased mechanical manipulation can compromise the structural integrity of the pelvic floor and surrounding tissues, leading to higher incidence of lacerations involving the anal sphincter.

In contrast, the other options, while they may have associations with obstetric procedures, are typically not as directly linked to the sequential use of vacuum and forceps as OASIS is. Infection, postpartum hemorrhage, and increased uterine atony may arise from certain delivery complications but are not specific risks tied to the use of both vacuum and forceps consecutively. Thus, the most distinct risk increase correlating with this specific delivery method is for OASIS.