Post-Fertilization Mechanisms

What to Know about Hormonal Methods

Think "oral contraceptives" prevent conception? Think again. Hormonal methods suppress ovulation much of the time, but scientists recognize that in many cases ovulation continues to occur.1 Some women who use hormonal methods ovulate every single cycle. So how do hormonal methods prevent conception? That depends on how you define "conception." Although most people think of conception as the joining of egg and sperm to form new life, in many medical circles the word "conception" has an alternate meaning--the implantation of the embryo into the uterus.2 When fertilization is not prevented, hormonal birth control methods commonly cause the expulsion of an embryo prior to implantation by changing the lining of the uterus so that it will not accept an embryo and by changing the way the fertilized ovum travels down the fallopian tube.3 This action has been termed by some as 'interceptive,' as opposed to contraceptive or abortive.4 This is an important distinction, because any woman interested in preventing fertilization will want to avoid using these methods. Although there are legitimate medical uses for some of these drugs, clinicians tend not to explain the interceptive effects to their patients, some being unaware themselves. Pharmaceutical companies minimize this mechanism of hormonal methods to prevent women of conscience from rejecting their products, as had occurred with the IUD.5

According to the authoritative medical textbook, Contraceptive Technology, to make an informed choice, concerned women must be notified about the mechanism of action. Women need to know that "all regular hormonal contraceptives (the pill, implant, injectable) and emergency contraceptive pills," may prevent pregnancy by "inhibiting implantation of a fertilized egg."6

Ever Controversial...7

  • "I feel chemical contraceptives have the potential to harm an embryo. And I decided based on moral and ethical grounds that I could no longer prescribe them." Mary Martin, MD, Ob/Gyn, Midwest City, OK
  • "I function better and sleep better at night knowing I'm not giving the Pill." Arthur Stehly, MD, Ob/Gyn, Los Angeles Area, CA
  • "After reading [about post-fertilization effects] in several other books and papers, I realized I could no longer justify prescribing the Pill. I think most women feel life begins at fertilization. When they find out about the post-fertilization effect, they're surprised and some even rethink their decision." Cynthia Jones-Nosacek, MD, Family Physician, Milwaukee, WI
  • "Refusing access to the Pill is a very disturbing trend. The war on choice is not just about abortion anymore." Gloria Feldt, President Planned Parenthood Federation of America
  • "We've known for a long time that birth control pills are abortifacients. Now it's finally catching on." Karen Brauer, M.S. R.Ph., Community Pharmacist, Lawrenceburg, IN
  • "We're seeing a growing trend among pharmacists and medical practitioners who consider it acceptable to impose their morality on women's bodies. I don't think moral aspects should be a concern." AD Lyerly, MD, Duke University Medical Center
  • "I found out in medical school that they may prevent fertilized eggs from implanting, and I decided then that I wasn't ever going to prescribe them." JB Stanford, MD, University of Utah

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