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What are the chances of pregnancy after taking plan B?

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Posted on Thu, 21 Jul 2016
Question: I have been taking Norethindrone Acetate (Agygestin) 5 mg for 13 days (since XXXXXXX 18). I had unprotected sex last night (did use the withdrawal method, however.) I also took Plan B today (13 hours later). My reasoning for taking the Aygestin was heavy bleeding on XXXXXXX 18, which stopped immediately (within 20 minutes--I have two fibroids and have had a myomectomy). I have had had zero bleeding since starting the Aygestin. I also took two ovulation predictor tests today, which were both negative. I am wondering what my chance of pregnancy is, especially since I am scheduled to have a hysterectomy on July 11. My app that predicts when I was to ovulate (except it hasn't taken in to consideration the Aygestin and that I stopped bleeding,) says I should have ovulated XXXXXXX 28. What are my pregnancy chances? I am hoping close to zero.
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Answered by Dr. Jacqueline Brown (21 minutes later)
Brief Answer:
Plan B alone will cut your pregnancy risk by 90 percent

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

In a healthy, normal ovulating woman, Plan B alone when taken within 72 hours of unprotected sex, reduces your risk of pregnancy to less than 10%.

In your case, with your history of fibroids, abnormal bleeding, and also having taken the hormone progesterone for 14 days prior to your active unprotected sex, the likelihood of having ovulated, let alone having conceived, is extraordinarily unlikely. In addition, you and your partner use the withdrawal method which is not as effective as hormonal contraception, but stillis successful in preventing pregnancy about 85% of the time.

So I really do not think that you need to be concerned about pregnancy at this time before your hysterectomy. As routine, the operating room will most likely check a blood pregnancy test within 2 to 3 days of the procedure as part of their standard preoperative evaluation. You will find out at that time if there are any problems, however the likelihood I really do believe is negligible.

I hope that I was able to adequately answer your question today, and that my advice was helpful. If I could be of any further assistance, please do not hesitate to contact me again.

Best wishes,

Dr. Brown
Above answer was peer-reviewed by : Dr. Yogesh D
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Follow up: Dr. Jacqueline Brown (8 minutes later)
Ok, so Aygestin at 5 mg. for 14 days would be helpful in preventing ovulation? The pharmacist could not find any info on it. He said typically .35 is in birth control, so he wasn't sure if 5 mg would work the same. My fibroids are small and intruterine, but I have had a myomectomy 3 years ago. I forgot to mention I do have hypothyroidism as well.

Oh, and I had read that Plan B wouldn't really be effective after ovulation. But you think there is a high chance I didn't ovulate, correct?
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Answered by Dr. Jacqueline Brown (34 minutes later)
Brief Answer:
Yes much lower doses of progesterone are used for contraception

Detailed Answer:
Hello again,

There have been no studies on the effectiveness of Norethrindrone Acetate alone as a contraceptive, but Plan B only has 1.5 mg of Levonorgeastrel, which is another kind of progesterone, which is a much lower dose than the Aygestin you were taking. There are many types of synthetic progesterone used in contraceptives, and they all work at similar doses. So it is not recommended to take progesterone (not designed to be a birth control pill) to prevent pregnancy, but it makes biologic sense why it would work that way.

So it is logical that you likely did not ovulate while you were taking the progesterone, and the Plan B added additional protection. It is true that emergency contraception cannot stop an egg that has already ovulated from being fertilized, but the egg only is viable for about 48 hours. So if that 48 hours has already passed, you are no longer at risk for pregnancy and therefore would have no additional benefit to taking Plan B. Your thyroid disease would not necessarily affect your fertility one way or another if it is under good control.

So again, I really do not think you have to worry about having conceived in your situation.

I hope this information clarifies your question.

Best of luck with your surgery,

Dr. Brown
Above answer was peer-reviewed by : Dr. Yogesh D
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Dr. Jacqueline Brown

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What are the chances of pregnancy after taking plan B?

Brief Answer: Plan B alone will cut your pregnancy risk by 90 percent Detailed Answer: Hello, and I hope I can help you today. In a healthy, normal ovulating woman, Plan B alone when taken within 72 hours of unprotected sex, reduces your risk of pregnancy to less than 10%. In your case, with your history of fibroids, abnormal bleeding, and also having taken the hormone progesterone for 14 days prior to your active unprotected sex, the likelihood of having ovulated, let alone having conceived, is extraordinarily unlikely. In addition, you and your partner use the withdrawal method which is not as effective as hormonal contraception, but stillis successful in preventing pregnancy about 85% of the time. So I really do not think that you need to be concerned about pregnancy at this time before your hysterectomy. As routine, the operating room will most likely check a blood pregnancy test within 2 to 3 days of the procedure as part of their standard preoperative evaluation. You will find out at that time if there are any problems, however the likelihood I really do believe is negligible. I hope that I was able to adequately answer your question today, and that my advice was helpful. If I could be of any further assistance, please do not hesitate to contact me again. Best wishes, Dr. Brown