Forceps delivery is classified based on station of the fetal head at application of the forceps and the degree of rotation necessary for delivery.
The risk of complications is less if the fetal head is lower and if less rotation is needed for delivery.
Outlet forceps:
(1) fetal head is at or on perineum OR fetal scalp is visible at introitus without separating the labia or fetal skull has reached pelvic floor
(2) sagittal suture is one of the following
(2a) anteroposterior (OA or OP)
(2b) right or left occiput anterior
(2c) right or left occiput posterior
(3) degree of rotation necessary for delivery: <= 45°
Low forceps:
(1) fetal head is at station +2 cm or more and not on pelvic floor
(2) without rotation: <= 45° and one of the following:
(2a) ROA or LOA to OA
(2b) ROP or LOP to OP
(3) degree of rotation necessary for delivery: > 45°
Mid forceps
(1) fetal head above station +2 cm with head engaged
where:
LOA = left occiput anterior
ROA = right occiput anterior
LOP = left occiput anterior
ROP = right occiput posterior
