Hey sezjm

sometimes with PROM the babes head will engage in a posterior position...leading to a posterior labor...but an active labor, with good postioning meant your pelvis was as 'open' as it could be for your baby to birth in the posterior position or 'sunny side up'

if you have a roomy pelvic cavity your baby will birth posterior..if you had perhaps been fearful, in bed, epidural etc you may well have ended up with either an instrumental delivery or a c/s

hope this answers your Q

xx yogababy