These convenient sponges are impregnated with a spermacide. They can be left in the woman's vagina for 24 hours, and provide protection from more than one act of intercourse during that period. The sponges weren't available for several years, but are going back on the market during the fall of 1999. That means that 10 out of a hundred women will conceive during a year of using a barrier method. All barrier methods provide some protection against sexually transmitted infections.
Most pills are a combination of the two different types of hormones, estrogen and a progestin .
In most cases the woman takes active pills for three weeks, then stops for a week. If she skips more than one pill, or if she is also on an antibiotic, using a barrier method for backup is a good idea. Another type of BCP's don't have any estrogen. They have to be taken every day, at the same time of day. It is best to take them in the evening.