Sponges are a modern reworking of an ancient method of— women used to dip a small piece of natural into oil or some other agent, and insert it into the vagina. The Today , which is now available over the counter, is quite a breakthrough in barrier methods. It is a soft domed disc of polyurethane about 5cm in diameter, shaped to fit snugly over the cervix; it has a tape across the back for removal. The sponge is impregnated with 1 g of spermicide (good old nonoxyno1-9 again).
Before use the sponge is taken out of its plastic sachet, dipped in water, and inserted into the vagina; the woman positions it over the cervix with her fingertips.
The sponge has to be left in place for six hours, like a cap, but can then be removed and thrown away — it is disposable. However, it can be left in place for up to two days with no extra spermicide. Some practitioners have suggested that it can even be washed and re-used once or twice, although eventually the spermicide will be washed out, but this is not recommended by the sponge’s developers. The sponge cannot be used by a woman who has a prolapse of the uterus or very poor muscle tone in the vagina, as the sponge would not stay in the correct position. Because the sponge doesn’t need to be covered with spermicide it is much less messy to use than a cap. It needs no prescription, and unlike caps does not have to be fitted by a trained practitioner; the Today sponges are all the same size. American trials suggested that the sponge was as reliable as the diaphragm, but the major British trial suggests that it has roughly twice the diaphragm’s failure rate, possibly as high as 25 pregnancies per 100 woman/years. Unfortunately, the current high retail price of the sponge could cancel out the benefit of its ready availability.