Factors associated with suboptimal instrument placement included fetal malposition ( OR 2.44 , 95 % CI 1.62-3 .66 ) , mid-cavity station ( OR 1.68 , 95 % CI 1.02-2 .78 ) , and forceps as the primary instrument ( OR 2.01 , 95 % CI 1.33-3 .04 ) .