And by keeping a fertilized egg from implanting.
If a woman takes the Pill regularly, how many times will she ovulate in a five year period? My understanding is that if the Pill is taken as prescribed and scheduled, most women won't ovulate at all. Thus, if a couple has sex 2x/week while the woman is on a pill, over a five-year period there will be zero embryos fertilized that do not implant.
Suppose the couple was not using any sort of birth control and had sex 2x/week. Over a five-year period, there'd probably be some birthable babies produced, but there would also probably be some fertilized embryos that would not implant.
To be sure, the fact that the Pill makes the uterine lining less receptive to a fertilized embryo could conceal its failures to prevent ovulation. So it may be difficult to ascertain what's really happening. But if the Pill is working as designed, it should minimize the number of embryos that are fertilized but fail to implant.
http://www.wdxcyber.com/bcp.htm
Thus, if a couple has sex 2x/week while the woman is on a pill, over a five-year period there will be zero embryos fertilized that do not implant.
Got a link to a study that can verify that claim?
So it may be difficult to ascertain what's really happening.
So any claims that there would be 0 fertilized eggs in 5 years are just opinion.