Brief Answer:
Plan B works 90 percent of the time taken within 72 hours of intercourse

Detailed Answer:
Hello, and I hope I can help you today.

Regardless of your medical history, Plan B works to prevent pregnancy if taken within 72 hours of unprotected sex about 90% of the time. So the effectiveness of Plan B is dependent upon how quickly you took it after the act of unprotected intercourse and whether you had sex during a period of time where an egg had already been released. There is no documented decreased effectiveness in women who are obese or have PCOS. Plan B works by thickening the mucus in the uterus and cervix making it more difficult for sperm to swim through the reproductive tract, and by reducing the risk of ovulation if has not already occurred for about 72 hours.

So at the most, you have a one in 10 chance of conceiving if you were ovulating at the time you had unprotected intercourse even if you took Plan B. It is impossible to know whether or not the medication will be effective, however in most cases if Plan B works, a woman will experience a small episode a vaginal bleeding between three and seven days after taking the medication. This is produced by a withdrawal of the hormones and is similar to a mini-period which is an indication that conception did not take place.

I hope I was able to adequately answer your question today, and that this information was reassuring. If I can be of any further assistance, please do not hesitate to contact me.

Best wishes and good luck,

Dr. Brown

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Brief Answer:
There is no way to know whether it will work or not based on symptoms

Detailed Answer:
Hello again,

It is true that there are studies that show that obese women have a lower peak hormone level after taking Plan B than in normal weight women. This is similar to the findings seen in the blood levels of daily birth control pills. However, there have been no actual trials to show that obese women have a higher failure rate of Plan B. Furthermore, most women do not have any symptoms from Plan B, so a lack of side effects cannot be used as a sign of failure.

In addition, if you had not ovulated before you had unprotected intercourse, you would not have a change of conceiving whether or not you took Plan B. This is true of women at any weight and is only dependent on the timing of your unprotected encounter in relation to when you ovulate. Ovulation apps are actually not completely accurate unless you have a 28 day cycle, because they assume you ovulate on Day #14. More accurately you typically ovulate 2 weeks before your period begins (rather than after) so in November you likely ovulated on the 23rd.

So it really is not possible to know in advance if the pill worked based on symptoms, the timing of your cycle (unless you have confirmation of your ovulation time with a urine or blood test) or your weight. The only way to find out is to wait for your period and see what happens. If you experience bleeding in the next 3-7 days, that is an encouraging sign. If not, urine pregnancy test will become positive within 10 days to two weeks of conception, so if you have not menstruated by then I recommend performing pregnancy test for confirmation.

If you are extremely anxious about your situation, since it is still within 72 hours of your act of unprotected intercourse, you could take a second dose of Plan B. There is no medical study that will show if this is more effective than having just taken the one pill, however it may ease your peace of mind as this is still within the window of time where Plan B is the most effective. The hormone in Plan B is not harmful and will not cause any medical risks or complications if you do not need the additional dose.

So in summary, it is true that there is a theoretical decreased effectiveness of hormonal contraceptives and obese women. There is no way to know for sure if you had already ovulated this cycle, but if you haven't, there is no way you could conceive even without Plan B. If you are still anxious about pregnancy, taking a second dose of Plan B may increase its potential effectiveness without causing any additional risk.

I hope this additional information was helpful and clarifies your situation.

Warm regards,

Dr. Brown

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Brief Answer:
There is no way to tell for sure if you ovulated this month

Detailed Answer:
So as I stated before, you typically ovulate 14 days before your date of menstruation.

So counting backwards: you likely ovulated on:

November 23
October 20
September 22
August 20

So the greatest likelihood is that you ovulated this month between the 20th and the 23rd.

Unfortunately, there is no way to know for sure if you already ovulated this month in particular unless at the time you had a hormone test or use an ovulation predictor kit, which tests for the surge of hormones which trigger ovulation.

However, even if you have ovulated, as I stated before, Plan B works in other ways to prevent pregnancy at a rate about 90%. Even though there are theoretical reasons to believe there may be decreased effectiveness in obese women, the greatest chance is still that the medicine was effective and you did not conceive.

I know it is difficult having to wait for a few weeks to know the outcome of this encounter but I assure you there is no accurate way to completely calculate your risk of pregnancy from one individual encounter.

I hope this additional information was helpful.

Take care,

Dr. Brown

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