Know Your Options

After unprotected sex, there is a three- to five-day window of opportunity to prevent pregnancy if you take immediate steps.  There are currently four options for emergency contraception in the United States: three different types of pills and the IUD.  Here are guidelines from Dr. Jenny M. Jaque, chief of obstetrics and gynecology at the Keck School of Medicine at the University of Southern California, to help you choose the one that’s right for you.

The options

  • One-Step and Plan B. These progestin-only pills are available as a single pill or as a two-pill dose taken 12 to 24 hours apart. They should be taken as soon as possible after having unprotected sex. Progestin pills are 75% effective in preventing an unplanned pregnancy, and their effectiveness decreases over time. They are most effective up to 72 hours or three days after unprotected sex, but may have some effect for up to five days. Progestin-only pills prevent pregnancy by preventing ovulation and will not affect an existing pregnancy. The advantages of using this type of emergency contraception are that you can take a one-pill dose without the side effects of the combined estrogen and progestin pills. You do not need a prescription for this type of emergency contraception, and it can be taken more than once during the same menstrual cycle (month).
  • Birth control pills that contain both estrogen and progestin. This method involves taking combined oral contraceptives in a higher number than usual. Given in two doses, the number of pills you need to take varies depending on the brand of birth control pills. The effectiveness of this method of emergency contraception also decreases over time (up to five days) and the pills should be taken as soon as possible after unprotected sex. Common side effects with this method are nausea, vomiting (more common than with progestin only), breast tenderness, bloating, and abdominal pain. You need a prescription for this method and will need to consult with your medical provider or a pharmacist to determine the number of pills you need to take based on the brand you have.

  • ella (Ulipristal), an anti-progestin. This may be taken up to five days following unprotected sex without losing any of its effectiveness. It is one pill, available by prescription only, that works by preventing ovulation and possibly by preventing implantation, or attachment to the uterus. We don’t fully know the long-term effects of this method of emergency contraception; therefore, repeated doses during one menstrual cycle are not advised. Common side effects include nausea, vomiting, breast tenderness, abdominal pain, and cramping. The advantage of this method is the up-to-five-day effectiveness and one-pill dosage. However, it is not available over the counter and requires a prescription.
  • Copper IUD. This can be inserted into your uterus by your medical provider up to five days following unprotected sex. Although more invasive (and expensive) than taking a pill, a benefit of this emergency contraception is that it can be left in place to provide you with long-term contraception for up to 10 years.

Which is best?

The IUD (intrauterine device) is by far the best option, according to Dr. James Trussell, faculty associate at Princeton University and researcher in the area of reproductive health, who has actively promoted making emergency contraception more widely available. “Of the four methods, the copper IUD is by far the most effective with a failure rate of less than 1% and the benefit of preventing pregnancy for 10 to 15 years,” he says. “It’s the only method that provides long-term protection. There is a misconception that IUDs frequently fall out, which is not true. Yes, bleeding does happen after insertion and it can be annoying, but it will gradually lessen. One of the disadvantages of over-the-counter pills is that women don’t have contact with clinicians, which makes them less likely to adopt effective long-term contraception.”

There are two different types of IUD available in the United States: the ParaGard and Mirena. The ParaGard IUD contains copper, and is effective for 12 years. The Mirena IUD releases a small amount of the hormone progestin. It is effective for five years.

Mirena, which has the same hormone as One-Step, is the most popular IUD because over time there’s considerably less blood loss with your period. The Mirena IUD may reduce period cramps and make your period lighter. On average, menstrual flow is reduced by 90%. For some women, periods stop altogether.

For more information from the experts:

Dr. Trussell maintains an emergency contraception website ( and a toll-free emergency contraception hotline (1-888-NOT-2-LATE).   

Dr. Jaque founded Health Goes Female ( with two other female MDs to provide women with accurate, reliable, and relevant health education.