Birth control gel, also called contraceptive gel, is a general term for a hormone-free substance used inside the vagina to prevent pregnancy. Depending on the type, this birth control works either by maintaining the normal acidic pH of the vagina and disabling or destroying sperm.

Recently, a new contraceptive gel known as Phexxi has become available in the United States. This is a gel that is placed in the vagina prior to penis-in-vagina sex.

Phexxi works by preventing the change in vaginal pH that happens when sperm are introduced. That makes it difficult for the sperm to travel and fertilize an egg.

Spermicide is a similar type of birth control that comes in a few different forms, such as foams, jellies, suppositories, tablets, and films. It’s typically placed into the vagina using an applicator. The substance makes it harder for sperm to reach an egg.

The only spermicide available in the United States is nonoxynol-9, which can be used alone or in combination with other barrier methods, such as condoms.

According to the manufacturer, Phexxi used on its own as directed by a doctor is 93 percent effective at preventing pregnancy, and 86 percent effective with typical use.

For comparison, spermicides are about 70 to 80 percent effective when used without other methods of contraception, according to a 2013 review of 14 trials. However, the researchers noted a wide range in the effectiveness, as many of the study participants did not complete the trials, which could have skewed the results.

I usually tell people that the most effective method of contraception is the one that you’ll use correctly and consistently. With that said, when doing a statistical comparison to some of the other methods out there, the contraceptive gels are much less effective than IUDs and hormonal implants.

Using a condom, diaphragm, or cap with the contraceptive gel can make it less likely that you’ll get pregnant. If your main goal is to prevent pregnancy, then it may be worth considering more effective methods out there.

The benefits of contraceptive gel are that it is nonhormonal and allows you to use it when you want. You don’t need to worry about taking it if you’re not planning to have sex. If you are using a gel or foam, you also have the added benefit of a lubricant.

On the flip side, you’ll have to plan ahead if you want to use the contraceptive gel. While most spermicides are available over-the-counter, Phexxi requires a prescription. You’ll also need to remember to insert the contraceptive gel in the vagina before penis-in-vagina sex.

The contraceptive gel can also cause bacterial vaginosis, yeast infection, genital discomfort (for either or both partners!), and burning symptoms in the area.

There are also reports of urinary tract infections (UTIs) and kidney infections in people who’ve used Phexxi. The contraceptive gel alone does not protect against sexually transmitted infections (STIs), but using it with barrier methods (like a condom) can prevent STIs.

No, there’s no lube with sperm-killing properties. While there’s data that shows that some lube is not the friendliest to sperm for people trying to conceive, a lubricant that does not contain spermicide is not effective by itself at preventing pregnancy.

For Phexxi, place the gel in the vagina using a pre-filled applicator immediately before or up to 1 hour before penis-in-vagina sex.

If more than an hour has elapsed, you need to reapply the gel. Also, if there’s going to be another round of penis-in-vagina sex, Phexxi will need to be reapplied.

For spermicide, follow the manufacturer’s instructions on how soon to apply before sex, as it can vary depending on which type you use.

You can use many other types of birth control with contraceptive gel to reduce your risk of pregnancy.

Just like with spermicides, Phexxi can be used with other barrier methods, like condoms, diaphragms, and cervical caps. And you can use it with the pill, patch, hormonal implant, and IUDs.

The one major exception is that vaginal rings should be avoided when using Phexxi.

To get Phexxi, you’ll need a prescription from a doctor. As an alternative, spermicides are available at your local pharmacy or anywhere that sells sexual wellness products.

Anyone who is using a vaginal ring for birth control should avoid using contraceptive gel. You also shouldn’t use Phexxi if you are prone to UTIs or have urinary tract abnormalities.

Anyone with sensitivities or allergies to Phexxi’s active ingredients (lactic acid, citric acid, and potassium bitartrate) or any other ingredients in the gel should avoid using it.

Dr. Carolyn Kay is an obstetrics and gynecology physician with special interests in reproductive health and family planning. Dr. Kay received her MD from the State University of New York at Upstate Medical University. She completed her residency at Hofstra Northwell School of Medicine.