Condom slipped off – will spermicide prevent pregnancy?


How effective is nonoxynol-9? The reason I ask is that my girlfriend and I had an incident when the condom slipped off of me while I was inside her. Is she at significant risk for getting pregnant? The condom we used had nonoxynol-9 on it, and I had already climaxed. One other thing that you might want to know is that she had just had her period.

—Concerned boyfriend

Dear Concerned boyfriend,

Bedroom mishaps can happen to even the most consistent contraceptive users, and can be a bit alarming, so looking for more information is a great idea. In short, yes, it's possible your girlfriend is still at risk for pregnancy. Although spermicide may be effective when used in conjunction with another form of contraception, such as a diaphragm, alone it is less reliable.

Spermcimide (nonoxynol-9 is the variety most commonly available in the U.S.) has been available for many years. In general, spermicide is not considered effective on its own, with a failure rate between 3 percent and 29 percent. Although spermicide does appear to boost the effectiveness of diaphragms, research on condoms and spermicide suggests that it does not increase condom effectiveness. Additionally, spermicide does not provide protection against STIs and may actually increase risk for certain STIs because of the irritation it can cause to the vaginal and anal area.

You mention that your girlfriend has just had her period, so it may come as some relief to hear that this is probably not her most fertile time. Women are most fertile during ovulation, which typically occurs around mid-cycle — ovulation happens 14 days before menstruation. That means that depending on the length of a woman's cycle (which can be anywhere from 24 to 42 days long, although it is typically between 26 and 32 days), ovulation could occur anywhere from 10 to 28 days after the start of her last period. Quite a range! However, a woman can track the length of her own cycle to get a better idea of when she may be ovulating.

During ovulation, the chance of pregnancy from a single act of sex without a contraceptive method has been estimated at 20 to 30 percent. The chance of pregnancy from a single act of sex where a contraceptive method was not used at other times in the cycle has been estimated at between 2 to 4 percent. Sperm can survive in the reproductive tract for up to 3 to 5 days, and emerging research has shown that some women may ovulate more than once per cycle, meaning that pregnancy can happen at seemingly unlikely times, even when a woman is on her period.

If you're concerned that your girlfriend may be at risk for pregnancy, emergency contraception (EC) may be a good option. Though it can work to prevent a pregnancy before it starts, it will not terminate an existing pregnancy. Plan B One-Step® and other generic one-pill formulations of EC are available without a prescription or proof-of-age to obtain and purchase. They can be found on-the-shelf at pharmacies and drug stores, typically near the family planning aisle. While it's most effective if used within 72 hours after sex that occurs when a method of birth control was not used or failed, it may be effective for up to 120 hours. Check with your local public hospitals, it is possible EC is available for free, 24 hours a day at any public hospital. Your girlfriend might also consider taking a pregnancy test; either by buying one at a pharmacy or making an appointment with her health care provider.

Although condoms are an effective form of contraception, mistakes happen. You and your girlfriend can stay prepared by being sure to use condoms correctly and always having a backup plan.

Last updated Apr 10, 2014
Originally published Oct 01, 1994

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