Does Plan B work after ovulation?
November 28, 2014 6:40 PM   Subscribe

If I ovulated yesterday, and had unprotected sex today (with withdrawal), will Plan B or a similar pill work? What I'm reading on their site and elsewhere indicates that it works by preventing ovulation, and there's no evidence that it prevents implantation. I'm sure I was ovulating yesterday, but not sure if I still am today (very possible). If there's a chance the pill will help I'll take it, but otherwise want to avoid it, because I know it will make me sick.
posted by anonymous to Health & Fitness (12 answers total) 4 users marked this as a favorite
There is a chance it will help. Per the website I'm reading, it may prevent implantation and may also prevent fertilization, which if you ovulated yesterday is probably too late, but today's still a statistical possibility that you haven't.

"It is possible that Plan B One-Step® may also work by preventing fertilization of an egg (the uniting of sperm with the egg) or by preventing attachment (implantation) to the uterus (womb)."

If you can take it right now, you can probably sleep off the worst side effects if you do indeed have them.
posted by Lyn Never at 6:49 PM on November 28, 2014 [1 favorite]

I would take it, endure the queasiness, and hope really hard that you don't get pregnant.
posted by Sara C. at 7:09 PM on November 28, 2014 [2 favorites]

Plan B does not seem to prevent pregnancy after ovulation, but (a) I'm not sure how you can be totally sure your ovary has already released an egg, and (b) there are other options, like ella, that may be effective after ovulation.
posted by jaguar at 7:12 PM on November 28, 2014

Yes, when in doubt, do take Plan B! Scarleteen has a lot of good information as well as as a message board monitored by their sexpert staff and volunteers.
posted by smorgasbord at 8:04 PM on November 28, 2014

Also, Plan B may make you sick but pregnancy -- and likely even worrying about whether you're pregnant or not -- would make you feel a LOT sicker.
posted by smorgasbord at 8:06 PM on November 28, 2014 [5 favorites]

I would definitely take it. It won't necessarily make you feel sick (if you are just theorizing, it doesn't make everyone feel sick - if you have taken it before and felt sick then that's different).

The sooner you take it, the more effective it has the chance to be.

If you don't use it, there's a zero percent chance it will help. If you do use it, there is at least a chance - if you really don't want to get pregnant, the risk:benefit equation seems pretty clearly towards taking EC even if it did make you feel transiently sick. Given unprotected sex around your time of ovulation, you are at high risk for undesired pregnancy, thus anything that can lower that risk is a good thing - at least a far better thing than going forward with an undesired pregnancy or getting a termination. That being said, the data suggests that EC is much less effective or may not be effective if taken after ovulation. Most people (especially women who are not tracking their basal body temp/cervical mucus etc) do not reliably know when they have ovulated, and the downside to taking EC is generally low, so the recommendation medically is to supply ALL women who have had unprotected sex within 120 hours with EC. As noted below, IUDs are an EC option that can be used anytime during a cycle, within 5 days of unprotected sex, and they are very effective.

Some quotes from a recent scientific review on emergency contraception:
"Ulipristal acetate (ella) is the most effective ECP available in the United States. In clinical trials, failure rates for ulipristal acetate range from 0.9% to 2.1%.4–6 Pregnancy rates following use of levonorgestrel ECPs in clinical trials range from 0.6% to 3.1%... The greater efficacy of ulipristal is most likely because of the fact that it is effective at disrupting ovulation even after the luteinizing hormone (LH) surge has begun, whereas levonorgestrel is ineffective after the start of the LH surge."

"Although ECPs are effective at reducing pregnancy risk for individuals, they have not been shown to reduce rates of unintended pregnancy or abortion at the population level. This finding may be due in part to the fact that, even when provided with ECPs in advance of need, women do not use them every time they are at risk. In one trial, 45% of women who were given an advance supply of ECPs who had unprotected sex did not use ECPs; in another trial, 33% of women with an advance supply of ECPs had unprotected sex at least once without using ECPs"

"Clinical guidelines recommend insertion of an IUD within 5 days of unprotected intercourse, or within 5 days of ovulation (if ovulation can reasonably be determined). However, a recent analysis showed that the copper IUD is highly effective at any point in the menstrual cycle, and can be used at any time as long as a negative urine pregnancy test result is obtained before insertion of the IUD."

"All ECPs should be taken as soon as possible after unprotected sex. ECPs work by interfering with ovulation, and because women frequently do not know precisely when they are at the most fertile period of their menstrual cycle, prompt use may improve the chance of preventing or disrupting ovulation."

"Two recent studies demonstrate that levonorgestrel ECPs, if taken before the LH surge has begun, can inhibit the LH surge, thereby disrupting the ovulatory process, but are ineffective thereafter. In these studies, a combined total of 492 women presenting for EC were monitored using blood serum and ultrasound to assess their cycle day. Among those who took EC before ovulation, none became pregnant, whereas 20 pregnancies would have been expected. Those who took EC on the day of ovulation or after became pregnant at the rate that would have been expected if no contraception had been used (11 women became pregnant, and 11 or 12 pregnancies would have been expected). These studies conclude that, because levonorgestrel ECPs are ineffective after ovulation has occurred, they do not interfere with the implantation of fertilized eggs. Levonorgestrel ECPs have been postulated to interfere with sperm function, tubal transport of sperm or egg, or endometrial receptivity, but evidence of these mechanisms is inconsistent across studies. Levonorgestrel ECPs have no effect if taken after implantation has occurred; the regimen does not affect an existing pregnancy or increase rates of miscarriage."

"Ulipristal acetate has been shown to prevent ovulation both before and after the LH surge has started (but before the LH peak), delaying follicular rupture for at least 5 days. In this study, ulipristal did not prevent ovulation in the vast majority of women treated with ulipristal after the LH peak. The fact that ulipristal is effective after the start of the LH surge, whereas levonorgestrel is not, may account for its greater effectiveness. Published postmarketing surveillance data for ulipristal acetate show no increased risk of miscarriage among women who took ulipristal when they were already pregnant, or became pregnant because of failure of ulipristal; in addition, exposure to ulipristal in utero did not increase the risk of birth defects among babies born."

Sorry for the length - I would just provide the link but the paper doesn't seem to be available freely as full text.
posted by treehorn+bunny at 9:01 PM on November 28, 2014 [11 favorites]

In the U.S. this would be an excellent question for Planned Parenthood, as they might discuss alternatives, and have less expensive cost, if it's your best option. Given the limited data, better to take it & have the weekend as a buffer for side effects.
posted by childofTethys at 5:56 AM on November 29, 2014

Everyone assesses risk differently and you should do what feels safest to you. But do keep in mind that if done properly (no semen getting near the vulva, man has peed since last ejaculation), withdrawal is pretty effective. About as effective as condoms.
posted by metasarah at 6:27 AM on November 29, 2014 [1 favorite]

Regarding the "it will make me sick" bit-- I took it once as a teenager and once in my twenties and the later time it wasn't nearly as bad, so there's a chance that your reaction won't be as terrible as you're expecting it to be. (Just an FYI in case you do take it, since dreading being sick seems to make that worse, even more so when you're also worried about pregnancy.)
posted by NoraReed at 7:34 AM on November 29, 2014

Mod note: This is a followup from the asker.
Thanks, everyone. The info about IUDs was particularly useful—I'd never heard that. I ended up taking the EC pill last night and managed not to throw up (which is what had happened the one other time I needed it). My local pharmacies didn't have Ella, so I took Plan B. However, I still believe it's likely the pill will not be effective. Even though I can't be 100% sure exactly when I ovulated, I have a very regular cycle with obvious EWCM, which had just stopped, along with Mittelschmerz, the day before.

I don't typically use withdrawal, but I've read more about it now and I'm feeling a little more comfortable. My partner pulled out 4-5 minutes before ejaculating, and has good self-control. We were both sober. As I'm in my thirties, I'm hoping that I'm also a little less fertile. I considered the IUD option, but I think I'm going to take my chances at this point. And never repeat this mistake again in the future.
posted by cortex (staff) at 7:52 AM on November 29, 2014

If it helps ease your mind any, when I was trying to GET pregnant using the fertility awareness method, sex on the day after ovulation was considered to be pretty unlikely to result in conception. Not impossible, and certainly not something you'd want to risk if you were trying to avoid rather than achieve pregnancy, but if I had a cycle where my only "fertile window" intercourse as on the day after ovulation, my chances of getting pregnant would not have been considered particularly high. And that's with fully completed ejaculation-in-vagina intercourse.
posted by KathrynT at 1:33 PM on November 29, 2014

Thanks for the follow-up. My fingers are crossed that everything works out!
posted by smorgasbord at 4:18 PM on November 29, 2014

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