A diaphragm is a silicone device used for contraception, classified as a barrier method of birth control. It is inserted into the vagina before intercourse to prevent pregnancy. A healthcare provider must first fit and prescribe the device to ensure the correct size is used for proper placement and effectiveness. The diaphragm is non-hormonal, fully reversible, and can be reused for up to two years with appropriate care.
The Dual Mechanism of Pregnancy Prevention
The diaphragm works by combining two distinct methods of contraception to block the path of sperm to the egg. Its primary function is mechanical, acting as a physical shield against the cervix, the opening to the uterus. When properly positioned, the device rests against the vaginal walls, completely covering the cervix and preventing sperm from entering the reproductive tract.
The second mechanism is the chemical action provided by spermicide, which must be applied to the diaphragm before insertion. Spermicides contain chemical agents that immobilize or destroy sperm. The diaphragm holds this spermicidal gel directly against the cervix, creating a locally high concentration of the active ingredient.
This dual approach is why the diaphragm is considered ineffective without the accompanying spermicide. The combined action significantly increases the reliability of the method compared to using the diaphragm or spermicide alone.
Essential Steps for Correct Use
Proper use begins with the professional fitting, as the diaphragm must be precisely sized to ensure it completely covers the cervix and remains securely in place. A provider determines the correct diameter and instructs the user on how to confirm proper placement. This step is foundational because an ill-fitting diaphragm can be easily dislodged during intercourse, leading to contraceptive failure.
Before insertion, spermicide must be applied to the cup of the diaphragm and around its rim. The device can be inserted up to two hours before intercourse. If intercourse occurs more than two hours after insertion, additional spermicide must be applied deep into the vagina without removing the diaphragm.
Following intercourse, the diaphragm must remain in place for a minimum of six hours to ensure all sperm present have been killed. If intercourse is repeated before the six-hour minimum has passed, a fresh dose of spermicide must be administered into the vagina with an applicator. After the required duration, the diaphragm is removed, washed with mild soap and water, air-dried, and stored for future use.
Success Rates and Safety Considerations
The effectiveness of the diaphragm is highly dependent on consistent and correct usage. With perfect use, the device can be up to 94% effective in preventing pregnancy over one year. However, the typical use rate, which accounts for human error such as incorrect sizing or forgetting to use spermicide, is closer to 83% to 87%. This difference highlights that user adherence is the most common reason for failure.
Diaphragm use may carry a few specific health risks. Some users report minor irritation of the vagina or penis, often a reaction to the spermicide. The positioning of the diaphragm can also put pressure on the urethra, which may increase the risk of developing urinary tract infections (UTIs).
A serious, though extremely rare, risk is Toxic Shock Syndrome (TSS), a severe bacterial infection. The TSS risk is associated with leaving the device in place for an extended period, which is why it is strictly recommended that the diaphragm not remain in the vagina for longer than 24 hours. The diaphragm provides no protection against Sexually Transmitted Infections (STIs).