What is a mixed delivery?

Vaginal with a C/S. A twin pregnancy may result in first baby being born vaginally, while twin b requires a c/section.
Public and private. In healthcare, a mixed delivery system is one that includes both public and private hospitals. Private for efficiency. Public for the common good. If your referring to childbirth, i'm not aware of this term. Although there are twin deliveries in which both a vaginal delivery and a c-section have occurred. This might reasonably be called a mixed delivery.