A “pro-life advocate from the Philippines,” who has quoted my research on the “post-fertilization” (abortifacient) effect of the birth control pill (BCP) in one of the most printed pro-life flyers in his country and also mentioned my research in a letter to the editor in the most read newspaper in the Philippines, was recently challenged by the Guttmacher Institute and sent me this question:
Dear Dr. Larimore,
I recently wrote this about you:

Dr. Walter Larimore, who for decades prescribed the pill, tried to disprove the claim that the pill is abortifacient, only to find 94 scientific studies proving that “postfertilization effects are operative to prevent clinically recognized pregnancy.” He published his findings in the scientific journal of the American Medical Association, and from then on stopped prescribing the pill. Shouldn’t we as a nation also stop prescribing a drug that kills our youngest Filipinos?

However, in reply to my letter (which discusses contraception, abortion and silent abortions), the Guttmacher Institute wrote:

… the birth control pill only serves to prevent a pregnancy; it does not terminate a pregnancy. It is blatantly false and against all scientific evidence to claim that the pill is an abortifacient.

Since Filipinos have a very high regard for American experts and doctors, may I ask you to help us in the prolife cause by clarifying this issue?
Many thanks for all your work in favor of life.
Raul
===================
Raul,
A careful reading of my and Dr. Stanford’s original article, an article to which the Guttmache Institute has, to date, had no published response, will explain the apparent contradiction.
In the article, we write: Many reproductive scientists have defined pregnancy as occurring at the point of or at some point after implantation. 
As the Guttmacher Institute states on their web site: According to both the scientific community and long-standing federal policy, a woman is considered pregnant only when a fertilized egg has implanted in the wall of her uterus; however, state definitions of pregnancy vary widely. The differences may be more than academic. 
Therefore, since the birth control pill (BCP) has no apparent effect on the pre-born child AFTER implantation, if one defines “pregnancy” as beginning at “implantation,” then the BCP is NOT and cannot be an “abortifacient.”
Using their definition of pregnancy, their statement about the BCP (“the birth control pill only serves to prevent a pregnancy; it does not terminate a pregnancy. It is blatantly false and against all scientific evidence to claim that the pill is an abortifacient”) is absolutely true.
But, you and they are talking about apples and oranges.
For, if you believe that life begins at conception, then any effect that ends the life of the unborn human woujld be an abortifacient effect, correct?
They talk about apples. You talk about oranges.
They say the BCP does not have an abortifacient effect. You say it does.
Who is right? It depends upon how you define pregancy. And, this case, you both are right — because you are using completely different definitions.
Dr. Stanford and I used the term “post-fertilization effects” instead of the term “abortifacient effect.” We write: Since there is variability in the definitions and use of terminology in reproductive medicine, we used the American Academy of Obstetrics and Gynecology Committee on Ethics’ definitions … 
… which includes pregnancy beginning at implantation. In other words, we used their language (not ours). We go on to write: For this review, we defined “postfertilization effects” to include mechanisms of action that operate after fertilization to prevent a clinically recognized intrauterine pregnancy. 
Now, if one believes life begins at conception, as we do, then a “post-fertilization effect” IS an “abortifacient effect.”
However, if one believes, as does Guttmacher, that pregancy does not begin until (or after) at implantation, then one can say, without fear of contradiction, that “the BCP is NOT an abortifacient.”
We go on to write: However, this definition (pregnancy begins at implantation) does not change the fact that some patients, for personal, scientific, moral, or religious reasons, identify the start of human life at fertilization. For such patients, a form of contraception that allows fertilization and then causes loss of the preembryo or embryo may be unacceptable. Regardless of the personal beliefs of the physician or provider about the mechanism of OCs, it is important that patients have information relevant to their own beliefs and value systems.
We go on to write: For some women or medical personnel who believe that human life begins at fertilization, the view that any postfertilization loss could be attributed to the effects of OCs and therefore could be considered induced rather than natural may render OCs morally unacceptable to use, even if the absolute frequency of such an event is very low.
For these reasons, when speaking or writing for the non-religious lay or professional communities, I define and use the term “post-fertilization effect” and not “abortifacient effect.”
With those who believe, as I do, that pregnancy begins at conception, the “post-fertilization effect” is, in point of fact, an “abortifacient effect.”
As the Master has taught us, “Behold, I am sending you out as sheep in the midst of wolves, so be wise as serpents and innocent as doves.” (Matthew 10:16,ESV)
Blessings in your work.
Walt Larimore, M.D.
========================
Here are some of my other blogs and writings on this very important topic:

• Even More Evidence That the BCP Causes Unrecognized Abortions
• “Does the Birth Control Pill Cause Abortions?” A Letter From A Reader.
• More Evidence That the BCP Causes Unrecognized Abortions
• New documentary features Dr. Walt and exposes abortifacient qualities of the birth control pill
• The Abortifacient Effect of the Birth Control Pill (A Reading List)
• American Society of Reproductive Medicine Statement Confirms the Pill Causes Abortion
• Professor Says Women Use Birth Control Pill Wrong, Resulting in Abortions
• Postfertilization effects of oral contraceptives and their relationship to informed consent
• Postfertilization effects of oral contraceptives and their relationship to informed consent (My Commentary on How This Study Changed My Beliefs and Practice)
• The Growing Debate About the Abortifacient Effect of the Birth Control Pill and the Principle of the Double Effect