It takes between 2 and 3 days for the embryonic development, that starts with the fertilized egg which is still within the fallopian tube. That developing embryo travels down the tube for 2 to 3 days before reaching the uterus.
The morning after pill is considered the pregnancy preventative after aware unsafe sex.
RU486 is specifically an abortion pill for after the feritilized agg makes it to the uterus.
Facts are facts - don't bring personal beliefs into it.