A diaphragm is a barrier form of birth control. Combined with spermicide, it prevents pregnancy by blocking the uterine opening, and by stopping the sperm from moving and fertilizing an egg

The device is a shallow, dome-shaped, rimmed cup that is placed in the vagina to cover the cervix.

Used correctly, it can be 94 percent effective in preventing unintended pregnancy.

Fast facts about diaphragm birth control

  • Types of diaphragm include the arching spring, coil spring, and flat spring diaphragms.
  • They can be 94 percent effective against unwanted pregnancy.
  • A diaphragm needs to be perfectly fitted for full effectiveness, and applied from 1 hour before until 6 hours after sex.
  • They are an immediately effective and reversible form of birth control.
  • Spermicide may act as an irritant and inflame urinary tract infections (UTIs) in those already prone to infection.

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Diaphragms are a form contraceptive that are effective 94 percent of the time when used perfectly.

A diaphragm, or cap, is a reusable, dome-shaped cup that fits over the cervix. It is made from latex or silicone. It is used with spermicide, a cream or gel that prevents the sperm from successfully fertilizing an egg.

There are several types.

The arching spring diaphragm is the most common type. It has a firm rim it is easier to insert. It is suitable for women with poor vaginal muscle tone.

The coil spring diaphragm has a soft, flexible rim. It is suitable for a woman who has average vaginal muscle tone.

The flat spring diaphragm has a thin, flexible rim. It works best for women who have strong vaginal muscle tone.

The flat spring and coil spring diaphragms can both be inserted with an introducer tool.

The wide seal rim diaphragm is a silicone ring that is useful for women who are allergic or sensitive to latex. It is available in arching spring or coil spring shapes.

Different sizes are available, but the standard size is 75 millimeters (mm) across. To get a good fit, your health care provider will carry out a physical examination.

How to use it

A healthcare provider will normally explain how to use a diaphragm correctly. They can teach the user if there is difficulty inserting or removing the diaphragm. An inserter device may help.

To use the diaphragm:

  1. Apply about a teaspoon of spermicide in the dome, and spread it around the rim.
  2. Fold the diaphragm in half, with the dome pointing down, and so that the two sides of the rim are touching
  3. Hold the vagina open with the other hand.
  4. Push the folded diaphragm as far into the vagina as possible, aiming back toward the tailbone.
  5. With one finger, push the front rim of the diaphragm up behind the pubic bone.
  6. Check the position of the diaphragm by placing your finger on the dome. You should feel your cervix through it. The cervix is the part that feels firm, but not bony.

If it is not correctly positioned, you may have to remove it and start again, remembering to reapply the spermicide.

The diaphragm can be put in place around 1 hour before having sex, and it should remain in place for at least 6 hours after intercourse. It must not be left in the vagina for more than 24 hours.

If the user is going to have intercourse again within 6 hours, more spermicide should be placed in the vagina, without removing the diaphragm.

It is important to note that diaphragms do not provide protection from contracting sexually transmitted infections (STIs).

Using a condom in addition to the diaphragm will reduce this risk and provide extra protection against unwanted pregnancy.

Used correctly and consistently, the diaphragm can be 94 percent effective in preventing pregnancy.

However, to be effective, it has to:

  • fit well
  • be correctly placed over the cervix
  • be used with spermicide
  • stay in for at least 6 hours

To increase effectiveness, the man can use a condom or pull out before ejaculation to further decrease the risk of pregnancy. Using a condom also reduces the risk of a sexually transmitted infection (STI), because a diaphragm does not protect against this.

Diaphragms are safe for most women to use, but for some women, they may not be suitable.

These include:

  • women who are uncomfortable with touching their vagina and vulva
  • those with a latex, silicone, or spermicide sensitivity
  • some women with a uterine or vaginal abnormality
  • those who find it too difficult to insert the diaphragm
  • women who have given birth within the last 6 weeks or who have recently undergone an abortion after the first trimester of pregnancy
  • those with frequent urinary tract infections (UTIs)
  • history of toxic shock syndrome
  • poor vaginal muscle tone
  • recent surgery to the cervix

A doctor can advise about alternative options.

All forms of birth control have both advantages and disadvantages.

A diaphragm can be a good option because it:

  • gives a woman control over her decisions to become pregnant
  • is safe to use during breastfeeding
  • is easily carried in a pocket or purse
  • has no effect on hormone levels
  • is immediately effective and immediately reversible
  • can be inserted several hours before vaginal intercourse
  • is not usually felt by either partner
  • is less invasive than an IUD or hormonal treatment and does not need regular doctor's visits

It can be safer than oral contraceptives for use by women over the age of 35 years and those who smoke, because there is no risk of cardiovascular problems.

Disadvantages

Disadvantages of using a diaphragm include:

  • difficulty with insertion
  • the possibility of the diaphragm moving, due to penis size, sexual position, or heavy thrusting
  • it needs to be inserted before every act of vaginal intercourse

A woman needs to be refitted for her diaphragm after each full-term pregnancy, abdominal or pelvic surgery, miscarriage, abortion after 14 weeks or a weight change of 20 percent, or around 15 pounds.

A diaphragm should be replaced every 1 to 2 years.

Some substances, such as petroleum jelly, should not be used with a diaphragm, as they can cause erosion in the material.

A diaphragm is unlikely to pose a health risk, and serious problems are rare.

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There is a slightly higher risk of a urinary tract infection with a diaphragm.

However, some problems may occur.

Urinary tract infections (UTIs) and vaginal irritation have been linked to diaphragm use.

Urinating before applying the diaphragm and after intercourse can help prevent a UTI.

Vaginal irritation may occur due to silicone sensitivity or as a reaction to the spermicide. If vaginal irritation occurs, it may be a good idea to use a different spermicide.

Most spermicides contain nonoxynol-9. This can become an irritant when used several times in a day, or if the user has HIV. It can increase the risk of contracting HIV and other STIs.

Anyone who is concerned about a UTI or vaginal irritation should speak to their health care provider.

Toxic shock syndrome (TSS) affects around 2.4 users in every 100,000, but this is usually after leaving the device in for over 24 hours.

It is important to consult a physician if the following symptoms occur:

  • burning with urination
  • discomfort when using the diaphragm
  • irregular spotting or bleeding
  • genital irritation
  • red or swollen vulva or vagina
  • unusual vaginal discharge
  • a high fever

Does it always work?

According to Planned Parenthood, diaphragm used perfectly is 94 percent effective. Overall, it is 88 percent effective, as people do make mistakes.

Other estimates put the success rate between 70 and 99 percent.

It is important to remember also that any birth control method that is not used according to the instructions may not be successful in preventing pregnancy.

A diaphragm is available from a health care provider or a family planning clinic and must be fitted by a health care provider.