In multivariate analysis , the Bloemfontein site [ odds ratio ( OR ) : 2.43 ; 95 % confidence interval ( CI ) : 1.32 to 4.48 ] and liking the pill color ( OR : 2.93 ; 95 % CI : 1.18 to 7.27 ) were positively associated with good adherence , whereas using oral contraceptive pills at enrollment was negatively associated with good adherence ( OR : 0.37 ; 95 % CI : 0.18 to 0.74 ) .