Kasbaoui et al reported criteria for a difficult extraction at delivery. The authors are from Strasbourg University in France.
Criteria for extraction difficulty - one or more of the following:
(1) operative vaginal delivery considered difficult by the operator
(2) >= 2 more vacuum device detachments (if vacuum device used)
(3) need to apply a second instrument
(4) extraction time > 10 minutes
(5) need for an internal obstetrical maneuver to disengage the shoulders
(6) cesarean section for extraction failure
Risk factors for difficult extraction:
(1) perineal to skull ultrasound distance (PSUD) > 40 mm
(2) birth weight > 4,000 grams
(3) presentation posterior or transverse
