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View Diary: Ron Paul okay with emergency contraception in cases of 'honest rape' (138 comments)

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  •  I'm trying to find info on this (0+ / 0-)

    I've heard it said that emergency contraception works only or mainly by preventing ovulation. But that has never made sense to me; how could Plan B work so well if it only prevented ovulation? Wouldn't a lot of women who took Plan B and were in danger of an unwanted pregnancy already have ovulated? What's the window of fertility-- doesn't it continue past ovulation? Let's say I ovulated yesterday and had sex today, couldn't I get pregnant?

    Anyway, here is one scientific paper on the issue:

    Mechanism of Action of Emergency Contraception
    Does plan B prevent fertilization as well as ovulation? Does it prevent implantation?

    •  The window on ovulation is about 24 hours . . . (1+ / 0-)
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      which is actually a pretty small window.  The problem is that sperm live for 3-5 days.  So you could have sex, and a few days later ovulate, and bam.  So in this sense, it would stop that type of slip up.

      OTOH, let's say you have intercourse the day you are ovulating, or just after (at the end of that 24 hour window), the sperm have to get there first, and they have a short window of time to do it.  So, if the cervical mucous isn't conducive to that, that's the other way.

      We don't know that much about implantation, really. It's possible that it stops implantation. It's conceivable that the pill stops implantation (it's really hard to look inside uteruses at that exact moment and know the causal factor).  
      Of course, for all we know, many fertilized eggs have been lost during a menses and nobody even knew it.  Plus, if that is the case, then the pill may be doing the same thing (and many other hormonal contraceptives.  

      -7.3,-7.5 If I can't dance, I don't want to be part of your revolution.

      by Nebraska Outsider on Mon Feb 06, 2012 at 12:38:07 PM PST

      [ Parent ]

      •  So do you mean (0+ / 0-)

        that an egg has about a 24 hour window to be fertilized by any sperm that might arrive?

        I see. So then if a woman has unprotected sex, she might have already ovulated and get pregnant, but she also has a much higher risk of the sperm hanging around waiting for any ovulation that happens in the next 3 to 5 days?

        •  exactly. (0+ / 0-)

          That's why preventing ovulation is the primary method that EC works, because of the sperm five day window.  Stopping ovulation brings the window down from 6/28 chance (five days for sperm plus 24 hours for egg)  to 1-3/28 chance, effectively halving it or more.  Of course most emergency contraception is taken in a 3 day window, but that's also why the sooner you take it, the more effective it is.  If you can get it down to a one day window of opportunity and then slow down the sperm (cervical mucous), chances of fertilization are small (but not non-existent as EC only stops approx. 90% of pregnancies (95% if taken in the first 24 hours)).  That 5% are where ovulation occurred the day of unprotected sex and the sperm were quick.  Only then is it about implantation, and obviously some do implant or this number would be 100%.  That's where the whole abortion debate comes in, because we don't know how it affects implantation.  We know some do implant though, so I think their argument is weak.  

          -7.3,-7.5 If I can't dance, I don't want to be part of your revolution.

          by Nebraska Outsider on Mon Feb 06, 2012 at 06:50:31 PM PST

          [ Parent ]

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