月經(jīng)具有規(guī)律的月經(jīng)周期、經(jīng)期、經(jīng)量等,而月經(jīng)周期、經(jīng)期、經(jīng)量任何一項異常都屬于功能性子宮出血。正常月經(jīng)周期為21-35天,月經(jīng)周期小于21天或大于35天均屬于功能性子宮出血。正常經(jīng)期一般持續(xù)3-7天,如經(jīng)期小于3天或大于7天均屬于經(jīng)期異常,可歸于功能性子宮出血范疇。正常經(jīng)量為經(jīng)期5-80ml,如經(jīng)量小于5ml或大于80ml則屬于功能性子宮出血。