Plan B works to prevent pregnancy by delaying ovulation. If you have sex without adequate contraception during ovulation, other options like the copper intrauterine device (IUD) may be more effective to prevent pregnancy.

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It’s really quite simple: No morning-after pill works during ovulation, as they’re designed to delay it.

If ovulation is already happening, Plan B (or any other emergency contraceptive pill) will have failed before it’s even begun. But knowing whether you’re ovulating can be tricky.

If there could be a risk that Plan B fails, the copper intrauterine device (IUD) is your best bet. Not only is it a highly effective emergency contraceptive, but it can also be used for long-term contraception.

The best way of preventing pregnancy throughout your cycle is to use a long-acting form of contraception.

There are several methods to choose from, including:

Barrier methods, such as condoms, are also an option. Although these methods are less effective than the above. Of course, you’d need to be using these before you have sex.

If you have sex without adequate contraception during ovulation, the copper IUD (ParaGard) is the safest emergency contraceptive.

You’ll need to have it inserted within 5 days after sex or ovulation for it to work.

Once in, the copper makes it difficult for sperm to reach the egg, reducing the chance of pregnancy by more than 99 percent.

Plus, you can keep it in for use as a regular contraceptive for up to 10 years.

Taking a morning after pill during ovulation won’t harm your body. But you may still become pregnant.

That’s because pills, like Plan B, can *delay* ovulation to prevent pregnancy. But if you’re already ovulating, an egg has already been released.

And sperm — which can live in your body for up to 6 days — is more likely to reach it.

In fact, some research has concluded that emergency contraceptive pills containing levonorgestrel, like Plan B, are ineffective when taken on the day of ovulation or after.

If you’re not sure where you are in your cycle and the morning-after pill is your only option, taking it may be worthwhile.

After all, you might have not ovulated yet, and it could make a difference.

Worth mentioning: Some morning-after pills are less effective for people who weigh more than 155 pounds, so keep that in mind as you decide which emergency contraceptive option is best for you.

If you’re able to, reach out to a doctor or other healthcare professional for help. Your local clinic or Planned Parenthood may be able to offer advice and provide you with the pill.

It’s a tough one. There are some physical signs to look out for.

For example, more or clearer vaginal discharge can be a sign that you’re ovulating. You may also experience tender breasts and bloating.

Hormone levels also rise at this time — you can measure this with a kit that you urinate on. Some people even use fertility or menstrual tracking apps to help them predict ovulation.

But even those who think they have a pretty good idea can be wrong.

Although ovulation tends to happen between 10 and 16 days before your period, the exact day can change from month to month.

Plus, it can be affected by the likes of diet and stress.

Plan B’s manufacturers say the morning after pill may prevent fertilization if ovulation has already happened.

But studies have disputed this, suggesting that the levonorgestrel pill has little to no effect after ovulation.

So what options do you have to prevent an unwanted pregnancy post-ovulation?

Again, the copper IUD is your best bet. It’s still effective after ovulation, with the ability to stop a fertilized egg from implanting.

This can be a costly upfront option, depending on your insurance, and it requires an appointment with a healthcare professional.

But your local clinic or Planned Parenthood may be able to help, too. If you’re in the United States and aren’t sure where to start, check out our state-by-state guide on accessing free or low-cost birth control and emergency contraception.

It all depends on when your period’s due.

If you consistently track your menstrual cycle and know exactly when your period should arrive, only take a test if it’s at least a week late.

Unfortunately, periods aren’t always the most predictable of things. So, if you’re not certain when it’s due, you may need to wait a little longer.

That’s because pregnancy tests work by detecting levels of human chorionic gonadotropin (HCG), a hormone that doesn’t show up straight away.

Taken Plan B or another emergency contraception pill? Wait 3 weeks to see if your period arrives before taking a pregnancy test.

If you didn’t take a morning-after pill, take a test 2 weeks after sex. You can always take another test a couple of weeks after the first one to double-check the result.

If your test comes back positive and you want to terminate the pregnancy, there are options.

The best first step is to book an appointment with a doctor or other healthcare professional. They’ll confirm your pregnancy and tell you about the available abortion procedures.

Generally, these fall into medical and surgical options. But they do differ, depending on where you live and how long you’ve been pregnant.

A medical abortion involves taking two pills: mifepristone and misoprostol. Sometimes, the first pill is taken in the clinic and the second at home. You can usually take the abortion pill until 11 weeks after the first day of your last period. However, the success rate goes down slightly after 7 weeks.

This option might not be suitable if you have an IUD fitted or if you have an ectopic pregnancy.

Surgical abortions are often used later in a pregnancy — beyond 16 weeks after your last period in some cases.

There are two types of surgical abortion: a suction abortion, or vacuum aspiration, empties the uterus via suction, while a dilation and evacuation (D&E) uses a combination of suction and instruments.

If you’re in the United States and aren’t sure how or where to access an abortion near you, our state-by-state guide can help.

Any time you feel unsure, reach out to a doctor or other healthcare professional.

That could be after having sex without a barrier and needing advice on emergency contraception, or it could be after getting a positive result from a pregnancy test.

You can even speak with a doctor about contraception in general. They’ll be able to advise you on safe, long-term options.

It can be difficult to know when you’re ovulating. Therefore, it can be hard to know whether Plan B or another emergency contraceptive pill will work.

To avoid the need for emergency contraception in the first place, you can talk with a doctor about long-term birth control methods, like the pill or implant.

And if you’ve taken Plan B but aren’t sure if it’s worked, take a pregnancy test 3 weeks later to be on the safe side.

Lauren Sharkey is a U.K.-based journalist and author specializing in women’s issues. When she isn’t trying to discover a way to banish migraines, she can be found uncovering the answers to your lurking health questions. She has also written a book profiling young female activists across the globe and is currently building a community of such resisters. Catch her on Twitter.