A diaphragm is a latex or silicone dome that covers the cervix to prevent sperm from entering the uterus.
There are four types of diaphragms:
Arching spring diaphragm
Coil spring diaphragm
Flat spring diaphragm
Wide seal rim diaphragm
The last type is made of silicone and is meant for people allergic or sensitive to latex. Your doctor can help you decide which diaphragm type is best for you.
Diaphragms do not protect against STIs. Condoms and dental dams are the only forms of contraception that can prevent STIs.
How to Use a Diaphragm
Diaphragms must be used with spermicide to prevent pregnancy. Spermicide is a foam, gel, or cream that kills sperm.

Apply 1 teaspoon of spermicide to the inside of the diaphragm, as well as around the rim.
Fold the diaphragm with the dome pointing down.
Insert the diaphragm into the vagina and aim for the tailbone.
Push the diaphragm as far back as it will go.
Push the front rim of the diaphragm behind the pubic bone.
If you have sex more than once, apply more spermicide to the vagina without removing the diaphragm.
After sex, leave the diaphragm in for at least 6 hours.
Hook your finger on the front rim, then pull down and out.
Safety Practices
Do not use a diaphragm during your period.
A diaphragm can be inserted up to 18 hours before sex
Do not leave a diaphragm in for more than 24 hours, as this can cause toxic shock syndrome or infection