Final answer:
The nurse should advise the client to leave the diaphragm in place for at least six hours after intercourse.
Step-by-step explanation:
The nurse should advise the client to leave the diaphragm in place for at least six hours after intercourse. A diaphragm is a barrier method of birth control that is inserted vaginally and covers the cervix to prevent sperm from entering the uterus. Leaving the diaphragm in place for a sufficient amount of time after intercourse ensures that the spermicide has enough time to kill any remaining sperm.