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  Vol. 9 No. 8, August 2000 TABLE OF CONTENTS
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Informed Consent for Postfertilization Effects of Hormonal and Surgical Forms of Birth Control for Women

Mark A. Sherfey, MD

Arch Fam Med. 2000;9:690-691.

I read with interest the article by Larimore and Stanford.1 It was indicated by the authors that their review of the medical literature showed that, in women using birth control pills (especially progestin-only pills), postfertilization effects may occur when the birth control pills have failed to prevent conception (defined in the article as fertilization), which stops development of the preembryo or embryo after conception. Subsequently, it was pointed out that for some patients (because of moral and religious reasons), the use of these agents would be unacceptable. In addition, there is evidence that postfertilization effects can also occur in women using nonpill forms of female hormone birth control. For example, the Norplant system contains a progestin, and it is reported that, like other progestin-only contraceptives, Norplant implants appear to have more than 1 mechanism of action.2-3 "Norplant supresses ovulation in at least half of menstrual cycles."2(pK60) Ovulation may occur in some of the remaining cycles, yet clinically recognized pregnancy is not common.2, 4-5 This is possibly due in part to postfertilization effects in operation at least 5 to 7 days after fertilization before human chorionic gonadotropin levels are detectable in the blood.6 "Norplant's mode of action is the same as for oral contraceptive pills."7(p70) "[W]hen fertilization may have occurred, the inadequate endometrial development will prevent implantation and hence normal embryonic development."3(p2) Furthermore, "Twenty percent of pregnancies in Norplant users are ectopic."7(p71) Also, for Depo-Provera, an injectable progestin, "Mechanisms of action are the same as for OCs [oral contraceptives]."7(p66) For Depo-Provera, "The major effect is inhibition of ovulation. Second, the endometrium becomes thin and does not secrete sufficient glycogen to support a blastocyst on entering the endometrial cavity."8(p382) "MPAE [Depo-Provera] causes the endometrium to become atrophic."8(p381) In Depo-Provera users, series have been reported with 1.3% to as high as 14.3% of pregnancies as being ectopic.9

The increased risk of ectopic pregnancy when pregnancy is diagnosed in women using birth control pills, compared with pregnant controls, was presented in the article as one of the forms of postfertilization effects. In addition to this hormonal method of birth control, ectopic pregnancy is also more common among pregnancies conceived after surgical female tubal sterilization. "As many as 50% of pregnancies after sterilization by electrocautery are ectopic."7(p88) Therefore, when pregnancy does occur after tubal sterilization (as the authors revealed can happen with the use of birth control pills), there is an increased extrauterine to intrauterine pregnancy ratio, suggesting that a postfertilization effect is in operation.

Since there are patients who, after understanding that birth control pills could in part work by postfertilization effects, will not take them, the authors recommend obtaining fully informed consent before prescribing a birth control pill. The authors concluded that the principles of informed consent necessitate that patients who may object to any postfertilization loss should be made aware of this information so that they can give fully informed consent for the use of birth control pills. With their conclusion in mind, it would be just as prudent to obtain fully informed consent in the same manner for the other methods of birth control, for which there is similar evidence for these postfertilization effects.

Obtaining informed consent of a general medical-legal nature to cover the possible adverse effects and complications of various methods of birth control is already a common practice. Yet to also educate interested patients specifically that there may be postfertilization effects would be a new practice for many physicians and health care providers.

PO Box 98
Monterey, TN 38574


1. Larimore WL, Stanford JB. Postfertilization effects of oral contraceptives and their relationship to informed consent. Arch Fam Med. 2000;9:126-133. FREE FULL TEXT
2. Rhinehart W, ed. Hormonal Contraception: New Longacting Methods. Baltimore, Md: Johns Hopkins University; March-April 1987. Population Reports 15:1 (Series K, #3).
3. Fraser IS, Tiitinen A, Affandi B, et al. Norplant consensus statement and background review. Contraception. 1998;57:1-9. FULL TEXT | ISI | PUBMED
4. Croxatto HB, Diaz S, Pavez M, Miranda P, Brandeis A. Plasma progesterone levels during long-term treatment with levonorgestrel Silastic implants. Acta Endocrinol (Copenh). 1982;101:307-311.
5. Shoupe D, Horenstein J, Mishell DR Jr, Lacarra M, Medearis A. Characteristics of ovarian follicular development in Norplant users. Fertil Steril. 1991;55:766-770. ISI | PUBMED
6. Segal SJ, Faundes A, Alvarez-Sanchez ZF, Vilja P, Branche V, Tuochima P. Norplant users: the mechanisms of contraceptive action. Fertil Steril. 1991:56:273-277.
7. Stenchever MA. Office Gynecology. St Louis, Mo: Mosby–Year Book Ind; 1996.
8. Mishell DR Jr. Pharmacokinetics of depot medroxyprogesterone actetate contraception. J Reprod Med. 1996;41(suppl 5):381-391.
9. Tatum HJ, Schmidt FH. Contraceptive and sterilization practices and extrauterine pregnancy: a realistic perspective. Fertil Steril. 1977;28:407-421. PUBMED

Joseph B. Stanford, MD, MSPH
Walt Larimore, MD
In reply

We appreciate the points made by Dr Sherfey, and agree that forms of birth control other than oral contraceptives may have postfertilization effects, and that patients who may object to such effects need to be informed of this to assure fully informed consent. As noted by Dr Sherfey, in the case of Norplant, the evidence is at least as strong as it is for progestin-only pills that postfertilization effects contribute substantially to the prevention of clinically recognized pregnancy.

Dr Sherfey also notes that conceptions that occur after female sterilization, while rare, are much more likely to result in ectopic pregnancy, a form of postfertilization loss. Certainly patients contemplating sterilization should be aware of this fact. Whether this will be of concern to patients highlights the important question: what magnitude must postfertilization effects have to be significant to patients? We believe that further research is urgently needed not only to give more precise estimates of the actual incidence of postfertilization loss for various forms of birth control, especially oral contraceptives, but also to understand what level of risk, if any, is acceptable to patients.

Department of Family and Preventive Medicine
University of Utah
50 N Medical Dr
Salt Lake City, UT 84132
(e-mail: jstanford{at}dfpm.utah.edu)

Kissimmee, Fla

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