the objective of a " clean catch " is for the urine not to pick up any bacteria from outside the body. when the urine passes from the body through the urethral meatus (the external opening to the urethra which is located just above the vagina) the stream could contact the labia and pick up bacteria from them. to perform a clean catch you separate the labia with your fingers then wipe down and away with the provided antimicrobial wipes to cleanse the area. usually you wipe more than once. this removes all external bacteria from the path of the urine. next you start the urine stream then move the cup into the stream for a clean catch. this way the urine washes away if you will any external bacteria from the urethral meatus. thus the urine specimen contains only cells and possible bacteria from within the bladder and urinary tract itself. this enables the health care provider to diagnose abnormal bacteria or a urinary tract infection (bladder infection). i hope that explains things for you!
why is it necessary to hold the labia open for clean catch midstream collection?