I accidentally had unprotected sex. How do I prevent pregnancy?

Updated December 4, 2024

Clinical Editor: Megan Dodson, PA-C

While not a planned scenario, we understand that unprotected sex happens — you missed a birth control pill, your regular method of birth control failed, or you had sex without a condom or barrier protection (you can still get pregnant with the pull out method). If you find yourself in any of these situations, there’s no need to panic. There are options for emergency contraception, both over-the-counter and available through your healthcare provider, that will significantly reduce your risk of becoming pregnant. Read on to learn more about your options for emergency contraception.

There are two main options to consider, the pill and the IUD

The pill:

Often referred to as the morning after pill, this is a hormone based medication that can delay ovulation (ovaries releasing eggs to be fertilized by a sperm) and significantly reduce your risk of getting pregnant. This is a great first line option for many women, but needs to be taken soon after sex, and effectiveness can be affected by your body mass index (BMI - a calculation based on your height and weight). Options for emergency contraception pills are Plan B (levonorgestrel - available over-the-counter) and Ella (ulipristal - available by prescription).

Intrauterine Device (IUD):

Intrauterine devices (IUDs) are the most effective form of emergency contraception, and they are also a great option for long-acting reversible contraception. IUDs work by interfering with egg fertilization, and they also help prevent implantation of the egg into the uterus.

Hormonal IUDs (Mirena or Liletta) release a small amount of the progesterone hormone over a long period of time. Both Mirena and Liletta provide effective birth control for 8 years. Hormonal IUDs can also make you have lighter periods, and they can help with menstrual cramping and PMS symptoms.

The copper IUD (Paragard) is a great hormone free version of long acting reversible contraception that can also be used for emergency contraception. When used as birth control, it is FDA approved for 10 years, but evidence tells us it is effective for up to 12 years. If you’re curious about having an IUD inserted, read more about what to expect.

The sooner you’re able to take the morning-after pill or have an IUD inserted, the better, but how long you can wait depends on which option you choose.

Plan B (levonorgestrel) is most effective when taken within 72 hours after sex. Ella, another version of the morning after pill, is effective up to 5 days after sex. IUDs can be inserted up to 5 days after sex. Again, sooner is better, so don’t delay if you would like to start an emergency contraception option.

IUDs are the most effective form of contraception - they are 99% effective if inserted within 5 days (120 hours) of unprotected intercourse, and they are not dependent on how much you weigh.

Plan B is up to 89% effective if taken within 72 hours after sex. While it may be used up to 5 days after unprotected sex, it is less effective on days 4 and 5. It is less effective for people whose BMI is > 26. The Ella morning after pill is up to 98% effective if taken within 120 hours after sex. It is up to 94% effective if your BMI is > 26, and it is less effective for people with a BMI > 35.

The pill:

Side effects of morning-after pills are similar to the birth control pill, and they’re often not serious when they do occur. If you experience side effects, they’ll most commonly include:

• Nausea
• Fatigue
• Lightheadedness
• Spotting between periods
• Heavier bleeding during your period
• Breast tenderness
• Cramps

These side effects usually go away within a few days. If you experience consistent discomfort after taking emergency contraceptive, talk to your primary care provider.

IUDs:

Risks of IUD insertion include: pain, bleeding, infection (very low risk), and perforation (very rare, will not cause infertility, and disability is extremely unlikely). Side effects of the IUDs after it has been inserted include: spotting between periods, headaches, nausea, breast pain, and bloating. Copper IUDs may cause heavier and longer menstrual bleeding (7-10 days) with more cramping.

Morning-after pills have not been shown to have a negative impact on future pregnancies. You can take them as often as needed.

IUDs also do not have a negative impact on future pregnancies. They can be removed at any time, and it’s possible to become pregnant as soon as the IUD comes out.

Aside from IUDs, emergency contraception shouldn’t be used as a replacement for regular birth control. Check out our guide to birth control to see if there’s a method that’s right for you.

Plan B is available at your local drugstore without a prescription. They might be in a locked case or behind the counter, so call ahead or ask the pharmacist if you don’t see them around. Ella is available by prescription only. Your primary care provider will work with you in finding the best option for your needs and send a prescription quickly to your local pharmacy.

If you decide to get an IUD, you’ll need to see your PCP or GYN to have it placed. Call your provider’s office ahead of time so they can plan accordingly and make sure you can receive an IUD in a timely manner.

Still curious about your options for emergency contraception? Book an appointment today to talk with a One Medical provider, or reach out to our virtual care team.

Originally published November 19, 2019