** I pulled the information below from www.drdrew.com or http://www.drdrew.com/article.asp?id=1171.  I found the simplest and easiest explanation I could.  Unfortunately because were in an election year abortion is a hot topic.  I think there are far more important things to be concerned with than a familial or personal choice, but everyone should be armed with accurate information, so they can make their own decision **
 
Q: Is the morning after and RU486 different?

RU486 is an abortion pill. It is a very powerful progesterone-blocking agent that, typically given with another medication, is extremely effective in inducing an abortion. Abortion is legal in this country and as part of the menu of options for inducing abortion, this pill has been made available. However, it requires special training of the physician in order for it to be given.

The morning-after pill is in fact the usual contraceptive pill given in slightly higher doses and it works in the same manner as the contraceptive bill.

Contraceptive pills work primarily by preventing ovulation. They basically trick your body into believing that you are pregnant so that the pituitary gland never releases a hormone which causes an ovum to be released from the ovary. Overwhelming evidence suggests that is exactly how the morning-after pill works.

The morning-after pill is given within 72 hours of an unprotected sexual encounter. Taken within 24 hours, it is 90-plus percent effective; taken within the first 48 hours, it is over 80 percent effective, and, if taken within the first 72 hours, it is overall 70 percent effective in preventing pregnancy.

Almost certainly by the same mechanism, pregnancy occurs within the 24 hours of releasing the egg. Sperm, however, can be available for conception for up to 72 hours after the intercourse occurs. If an egg has already been released at the time that there is sexual intercourse, pregnancy will occur and this pill probably will have no effect on that pregnancy -- certainly no deleterious effect. If the egg has yet to be released, this pill will prevent that from occurring during that 72-hour window when the sperm could cause a conception.

There is some argument as to whether one of the mechanisms whereby this pill works is through altering the lining of the uterus to make it inhospitable to implantation of a fertilized egg. I am strongly of the opinion that the morning-after pill is no more likely to work by this mechanism than the oral contraceptive pill the way it is usually taken - and, for that matter, other anti-inflammatory agents such as Vioxx or Celebrex.

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