History has a way of repeating itself. Women throughout history have used various methods to prevent pregnancy, including using a sponge to block and absorb semen. The sponge sometimes was soaked in substances thought to weaken or inhibit sperm, such as vinegar, brandy or olive oil.

Although modern medicine doesn't support such practices, these basic principles have influenced the design and function of the contemporary contraceptive sponge — a soft, foam device that contains spermicide and covers the cervix. You may be among the women who prefer this form of contraception, which contains no hormones, requires no prescription and can be kept in place up to 24 hours.

Learn more about the contraceptive sponge, to help decide if it's the best birth control method for you.

The contraceptive sponge, which contains spermicide, fits over the cervix to block and absorb semen and kill sperm. The string loop helps with removal.

The sponge, a soft, disk-shaped device made from polyurethane foam, fits over the opening of a woman's uterus (cervix) to block and absorb semen. It's available without a doctor's prescription and requires no special fitting. This single-use, disposable sponge also contains a spermicide that's released slowly over 24 hours.

The Food and Drug Administration (FDA) approved the contraceptive sponge (Today Sponge) for the U.S. market in 1983. It quickly gained popularity as more than 90 million sponges were sold during the first 4 years after its release.

The Today Sponge was taken off the market in 1994, however, after the FDA reported that it had found that water at the company's factory was contaminated. And rather than invest in improvements to meet manufacturing standards, the company stopped making the sponge.

Now produced by a different company, the Today Sponge is sold in Canada. It's expected to be available in U.S retail stores if it receives FDA approval. Other sponges, such as the Protectaid Sponge and the Pharmatex Sponge, are available outside the United States.

The contraceptive sponge prevents pregnancy in three ways. It:

• Blocks the cervix so semen can't enter the uterus
• Contains spermicide nonoxynol-9, which kills sperm
• Traps and absorbs semen

Before inserting the sponge, first wash your hands so that you don't introduce germs into your vagina. Then, wet the sponge thoroughly with tap water to activate the spermicide. Squeeze the sponge gently until sudsy. Place the sponge in your vagina — with the dimple-side facing up and the string loop facing down — so that it tightly covers the cervix. The walls of your upper vagina hold the sponge in place. And the cup-like indentation helps keep the sponge centered on your cervix.

Insert the sponge before sexual intercourse and leave in place for at least 6 hours afterward. Protection begins once you insert the sponge and lasts up to 24 hours — the amount of time the spermicide is effective. Once you remove the sponge, you're no longer protected against pregnancy.

To remove, pull the sponge out of your vagina using the string loop. Occasionally, the sponge may turn upside down, making the loop hard to reach. If this happens, slide your finger around the edge of the sponge to find the loop. Or grasp the edge of the sponge with two fingers and gently pull. Sometimes the sponge may adhere to the cervix because of suction. If this happens, use your finger to lift the sponge away from the cervix on one side, breaking the seal. Then, you can remove the sponge normally.

If you can't remove the sponge or if you remove only a portion of the sponge, contact your doctor.

Yes, the contraceptive sponge is a reversible form of birth control. The sponge's protection diminishes after 24 hours, making pregnancy possible almost immediately.

Like other forms of birth control, the effectiveness rate of the sponge varies depending on how carefully you use it. For those who don't use the sponge correctly each and every time, the effectiveness rate is about 84 percent to 87 percent. Highly motivated couples who use the sponge perfectly every time may achieve effectiveness of up to 91 percent. By comparison, the birth control pill, with perfect use, can reach 99-percent effectiveness.

Other factors may decrease the effectiveness of the sponge:

• Certain vaginal or uterine conditions, such as when abnormal connective tissue divides the vaginal canal (vaginal septum) or when the uterus drops into the vaginal canal (uterine prolapse). These conditions may affect how the sponge fits on the cervix. Check with your doctor if you have concerns.

• Medications for vaginal yeast infections, such as topical creams and suppositories. These medications dilute the spermicide, lowering its effectiveness.

• Whether you have given birth. The birth process stretches the vagina and cervix, which may affect how the sponge fits on the cervix. Check with your doctor if you have concerns.

Some women using the contraceptive sponge have reported cases of toxic shock syndrome (TSS) — a rare, life-threatening bacterial infection. Warning signs of TSS include:

• Fever
• Nausea
• Vomiting
• Diarrhea
• Muscle pain
• Dizziness
• Faintness
• Sunburn-like rash on your face or body

Because of the risk of TSS, don't leave the sponge in place for more than 30 hours, and don't use the sponge while you're menstruating or if you have a history of TSS.

In addition, don't use the contraceptive sponge if you're allergic or sensitive to the spermicide nonoxynol-9. Also, wait 6 weeks after giving birth to allow time for your uterus to return to normal size. If you've had a miscarriage or other termination of pregnancy, your doctor can help you determine the best time to begin using the sponge.

Because it acts as a barrier and tries to stop fluids from entering the uterus, you might think the contraceptive sponge provides some protection against sexually transmitted diseases (STDs), such as HIV/AIDS and gonorrhea. However, bodily fluids that carry STDs can still come in contact with your vagina and vulva and may bypass the sponge and enter the uterus after removal. Therefore, contraceptive sponges aren't an effective means of protection against these diseases.

A single contraceptive sponge costs about $3.

The Today Sponge is sold in Canada. It will be available in U.S. retail outlets if it receives FDA approval.