Does Conception Occur at Fertilization, or Implantation?

Earlier today I was chatting with a pro-choice friend of mine about the terms "fertilization" and "conception". To me, these two words are synonymous. When the sperm and the egg unite, the egg is fertilized, and conception occurs. To my friend, however, these two words have very different meanings. When I asked what the difference was, she said that fertilization occurs when the sperm and the egg unite, but conception doesn't occur until the fertilized egg implants itself in the uterine wall. I asked her where she got this information, and she said that she got it from "medical books."

After doing some research, I discovered that the distinction between fertilization and conception isn't as clear cut as my friend wanted me to believe. According to Wikipedia, "Fertilization (also known as conception, fecundation and syngamy), is the fusion of gametes to produce a new organism." [1] According to About.com, "Conception is when the female's egg is fertilized by a male's sperm." [2] According to the Merck medical manual, "For conception (fertilization) [to occur], a live sperm must unite with an ovum in a fallopian tube with normally functioning epithelium" [3] However, according to Ovulation-Calculator.com, "cell division and implantation of the egg must take place for conception to be successful." [4] According to Guttmacher.org, a pro-abortion organization, "A pregnancy is considered to be established only when the process of implantation is complete" [5]

So why all the confusion as to whether fertilization and conception occur at the same time, or not? According to PhysiciansForLife.org, conception "was redefined by contraception & abortion promoters in the 1960’s to mean 'implantation in the uterus', not 'fertilization'. " [6] After further research, I discovered that it was the American College of Obstetrics and Gynecology (ACOG) that redefined conception in 1965. ACOG is a known supporter of abortion rights. Even though ACOG redefined the point at which conception (pregnancy) occurs, it appears that many people in the medical community didn't get the message, and still believe that conception occurs at fertilization. Results of survey taken by the Louisville Ob/Gyn Society showed that 73% of the respondents indicated that conception occurs at fertilization.[7]  

So what difference does it make if conception occurs at fertilization or implantation? It makes a big difference in regards to hot button reproductive issues such as in-vitro fertilization (IVF), cloning, stem cell research, and the use of so called pregnancy prevention drugs such as Plan B. If conception (pregnancy) occurs at implantation, the disposal of the fertilized egg after fertilization but prior to implantation can be considered contraception, instead of abortion. By saying that conception occurs at implantation, abortion rights supporters can claim that the use of drugs like Plan B prior to implantation does not result in an abortion. If conception occurs at fertilization, Plan B would be considered an abortifacient, which would most likely deter many women from using it. If less women use Plan B, the drug companies that make Plan B make less money.

Since there appears to be ambiguity in the medical community as to whether conception occurs at fertilization or implantation, how can a person decide which is the case? For a person that only has the civil law and secular culture to gauge what is true or not, it is a difficult question to answer. As a Catholic, I can defer to the teachings of the Catholic Church regarding when life begins. According to the Catholic Church, "Pregnancy, in fact, begins with fertilization and not with the implantation of the blastocyst in the uterine wall" [8]

References:

[1] http://en.wikipedia.org/wiki/Human_fertilization

[2] http://contraception.about.com/od/contraceptionoverview/p/conception.htm

[3] http://www.merck.com/mmpe/sec18/ch258/ch258a.html?qt=conception&alt=sh

[4] http://www.ovulation-calculator.com/pregnancy/pregnancy-conception.htm

[5] http://www.guttmacher.org/pubs/tgr/08/2/gr080207.html

[6] http://www.physiciansforlife.org/content/view/1170/2/

[7] http://www.informaworld.com/smpp/content~content=a907299020&db=all

[8] Statement on the So-Called "Morning After Pill" http://www.vatican.va/roman_curia/pontifical_academies/acdlife/documents/rc_pa_acdlife_doc_20001031_pillola-giorno-dopo_en.html