I had a retained placenta with DD#1. It was an awful labour and i was petrified of going thru it again with pregnancy #2 ( i was later told, docs even discussed a hysterectomy for me when in theatre......)...anyway none of my last two pregnancies were considered high risk and the third stage of labour was quick and successful.
YOu should discuss your fears and concerns with docs, midwives etc once you become pregnant. I know the fear of having another retained placenta was plastered all over my hospital notes - the medical staff were certainly aware of my history when i was in labour with DD#2.........