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Morning-after pill effectiveness

by Dr. Margo Harrison
Julie Medical Advisor

How effective is the morning-after pill?

Levonorgestrel, most commonly referred to as the morning-after pill, is an emergency contraception pill that can reduce the risk of pregnancy by up to 89% if taken within 72 hours after unprotected sex. It’s proven to be even *more* effective if taken within 24 hours, so it’s always best to take it ASAP.

Levonorgestrel is the active ingredient in Julie and was initially approved by the FDA in 1999. It’s been used by millions of women for decades and is an effective emergency contraception option for stopping a pregnancy before it starts.

Fun fact: levonorgestrel is the most used form of emergency contraception around the world.

If you just had sex and you’re unsure whether you were fully protected, take the morning-after pill, like Julie, as soon as possible. Remember, you can easily find Julie at your local Walmart or purchase it online. Julie’s packaging is discrete and designed to look nothing like other morning-after pills, so you don’t have to worry if you run into someone you know.

Weight does impact the effectiveness of the morning-after pill

If you’re over 165 lbs, the morning-after pill may not be the best option for you. In 2009, a study found that women taking emergency contraception with a higher BMI had a 3x greater risk of pregnancy than women with lower BMIs. Research, unfortunately, doesn’t know why. But you still have options. Ella® is another type of emergency contraception pill that works for women up to 195 lbs. Like Julie, it’s a one-time pill, but it does require a prescription. The copper IUD is not affected by weight at all, but it does need to be inserted by a healthcare professional up to 5 days after having unprotected sex.

What you need to know about levonorgestrel

Levonorgestrel is a progestin (a synthetic form of your body’s natural hormone progesterone), found in most oral and IUD contraceptives. However, the morning-after pill, like Julie, contains a much higher dose of progestin than daily birth control. Julie should not be used as a regular birth control method, because it's not as effective as regular birth control. It works by attaching to the progesterone and androgen receptors, which slows the release of gonadotropin-releasing hormone (GnRH) from the hypothalamus. This process suppresses the normal luteinizing hormone (LH) surge that precedes ovulation, which stops your ovaries from releasing an egg.

Depending on where you are in your cycle, the morning-after pill helps to prevent or delay ovulation, and prohibit sperm from fertilizing an egg. It’s important to remember that levonorgestrel is *not* the abortion pill; it will not induce an abortion or miscarriage, and won’t work if you are already pregnant—nor will it harm a fetus. Levonorgestrel helps to prevent pregnancy. It does not reverse it. The morning-after pill like Julie is legal without a prescription in all 50 states.

How effective is the morning-after pill when ovulating?

Julie (levonorgestrel) is most effective when taken before ovulation (about mid-way through your cycle) because it will stop the ovaries from releasing an egg, making it unavailable for a sperm to fertilize after unprotected sex. The ovulation window only lasts about 12-24 hours, and if taken during this time, some evidence suggests that the morning-after pill might be less effective. However, if you’ve already ovulated, it is possible that Julie can prevent sperm from fertilizing an egg or attaching to the uterus. It’s recommended to take a pregnancy test 2 weeks after you take the morning-after pill just in case.

How to know if you’re ovulating

Tracking your cycle is an easy, helpful way to know what stage of your menstrual cycle you’re in, like when you’re ovulating and what days you’re most fertile. On the days that you’re ovulating, it’s especially important to be very cautious with contraception. Ovulation usually begins mid-way through your cycle, about 10-16 days before your period starts.

Some ways to tell that you’re ovulating:

-Basal body temperature falls slightly, then rises again

-Cervical mucus or discharge becomes clearer, thinner, and more slippery

-Sex drive increases

-Light spotting

-Vulva or vagina might appear swollen

-Mild cramps in lower abdomen

There are a number of tools to help you track your cycle from period tracking apps to taking your basal body temperature every morning. If you prefer to go old school, tracking your period with a calendar works just as well.

How long are you protected against pregnancy?

Morning-after pills, like Julie, work retroactively—meaning they can protect you from pregnancy if taken within 3 days after having unprotected sex (they can work up to 5 days after unprotected sex, but it’s most effective the sooner you take it). Once you’ve taken the pill, the hormones will be active in your body for around 5 days, protecting you from sperm cells that can survive inside you for roughly the same amount of time.

The morning-after pill does not protect you against future unprotected sex, so you’ll want to continue using your regular form of birth control immediately after taking Julie.

Julie won’t affect your fertility

Julie is not a permanent form of birth control—it only stops ovulation in the short term. When you start a new cycle next month, you’ll go through a brand new ovulation phase, which is a new opportunity to get pregnant. So if you’re planning on having babies in the future, rest assured your chances of getting pregnant won’t be affected by Julie, even if you take it multiple times.

Need Julie now? Find a Walmart near you or buy a pack online to have on hand.

When used as directed, Julie is safe and effective. Common side effects may include changes in your period, nausea, lower stomach pain, tiredness, headache, dizziness and breast tenderness. Julie will not protect you from HIV and other sexually transmitted diseases.

This article is for informational purposes only and does not constitute medical advice. Always talk to your doctor about the risks and benefits of any medication.