Spermicides contain a chemical that either kills or damages sperm. Thus, sperm is rendered incapable of traveling through the cervix and uterus to the fallopian tubes, the usual site where it joins with an egg. If the two never meet, then nature’s way for pregnancy is averted.
A spermicide performs as a birth control if it is present at the time sperm is deposited. So, you must insert the product beforehand. Suggested time span is between 15 minutes to an hour ahead of ejaculation. (Not sooner, nor later.) Afterwards, it is best to leave the chemical killer in place for up to 8 hours.
To control birth, spermicide effectiveness is better than nothing. But less effective than other forms of birth control when used alone. Why? Because some sperm might survive. For those that do survive, a cervical barrier to help prevent sperm entry is a good complement, like a cervical cap, condom or diaphragm.
If spermicide effectiveness is so poor, why are they used? Because they are convenient, inexpensive, easy to use and have no affect on hormones. Generally, birth control pills and shots are very effective. But they can disrupt natural female hormone balance, which results in reproductive related issues and infertility for a long period after cessation. So for some women, these side effects outweigh the benefit of effectiveness.
Using a spermicide can be messy, unromantic and is associated with some health related problems. For instance, you could experience an allergic reaction to its chemicals, which results in vulvitis, cervicitis, urethritis or penal skin irritation. Another issue is recurrent urinary tract infections because the chemicals destroy healthy bacteria leading to an imbalance.
Finally, using spermicides do not reduce your risk of contracting an STD. Therefore, you MUST employ another protective measure, namely abstinence, monogamy or a condom.