RESULTS	Variables significantly associated with postpartum fever were ( 1 ) clinical chorioamnionitis ( odds ratio 5.37 ) , ( 2 ) duration of active labor : > or = 12 , 9 to < 12 , 6 to < 9 , 2 to < 6 hours ( vs < 3 hours ) ( odds ratio 4.86 , 3.53 , 3.46 , 3.04 ) , ( 3 ) cesarean section , operative vaginal delivery ( odds ratio 3.97 , 1.86 ) , ( 4 ) group B streptococcal colonization ( odds ratio 1.88 ) , and ( 5 ) maternal antibiotics before delivery ( odds ratio 1.94 ) .\