What defines the outlet forceps criteria during delivery?

The outlet forceps criteria during delivery are primarily determined by the position of the fetal head in relation to the pelvis. For outlet forceps to be used, the key defining criteria is that the scalp must be visible at the introitus – meaning that the fetal head has descended to such an extent that you can see it at the vaginal opening. This visibility indicates that the fetal head is in the outlet of the pelvis and is in the correct position for instrument-assisted delivery.

When the scalp is visible, it confirms that the fetal head is engaged and has reached a critical point in the birthing process, allowing for forceps to be safely applied. Other criteria, such as whether the hips are flexed, the condition of the membranes, or the leading point of the skull relative to the zero station, play a role but are not definitive for the specific requirement of outlet applicability. Thus, seeing the scalp at the introitus is the primary and most significant factor in defining the suitability for outlet forceps delivery.