How Do the Pill and Other Contraceptives Work? con't (page 3)

1  2  3  4  »

Addendum: Response to the arguments put forth in the brochure entitled: Hormonal Contraceptives: Are they Abortifacients?

Introduction: In January, 1998, a group of 22 physicians (almost all are Ob/Gyns) wrote a collaborative report addressing the question of the abortifacient nature of the oral contraceptive pill (OCP) [2]. Their three main arguments (found on page 7 in their booklet) are presented here, with a corresponding rebuttal to each by Dr. Kahlenborn:

1: They write:

"We know of no existing scientific studies that validate the 'hormonal contraception is partly abortifacient' theory. 'On-pill' pregnancy rates roughly parallel 'on-pill' ovulation rates (about 3-5% on 35 mcg pill). Increased spontaneous abortion of "on-pill" pregnancies is not noted."


(Here, the term "pregnancy rate" refers to the rate of pregnancy as confirmed by a positive pregnancy test, while acknowledging that a woman is actually pregnant before one can measure it [ie, directly after conception]).

The claim that "on-pill" pregnancy rates roughly parallel "on-pill" ovulation rates may appear to be a satisfying argument, but on closer examination this contention actually bolsters the argument in favor of the OCP acting as an abortifacient. Why?

If a woman is taking the OCP she will experience an artificially regulated cycle that lasts 28 days, so she will have about 13 cycles per year (365 days divided by 28). Thus a group of 100 women would be expected to have a total of 1300 cycles per year. If women taking the OCP experience a breakthrough ovulation rate (ie, "on-pill" ovulation rate) of between 3% to 5%, a group of 100 women would be expected to have between 39 to 65 breakthrough cycles in one year (1300 x 3% - 5%). William's Obstetrics notes that the average woman has a "natural fecundibility rate" of 28 percent.[33] ("Natural Fecundiblity rate," perhaps more accurately called the fertility rate, is defined in this section of William's Obstetrics as liveborn infants per ovarian cycle).

But William's Obstetrics also notes that for every 600 liveborn children, 279 embryos or fetuses are miscarried, 176 of them after a positive pregnancy test and 103 of them prior to being able to detect that a woman is pregnant. This means that the average couple will actually have a detectable pregnancy rate of: 28% + (176/600 x 28%) = 36.2%.* So a group of 100 woman who are sexually active and using the oral contraceptive pill, might expect between 14 and 24 detectable pregnancies per year: (ie from 36.2% x 39 to 36.2% x 66). But the PDR (Physician's Desk Reference) notes that a group of 100 women who are using OCPs in a consistent manner will have about 3 pregnancies per year 42  and a 1996 study by Potter [7] yielded an updated statistic of 7 pregnancies per year. In other words, if the condition that "on-pill" pregnancy rates roughly parallel "on-pill" ovulation rates is true, then the conclusion that the OCP does not act as an abortifacient is highly suspect. This is because if the ovulation rate is 3% to 5%, we might expect the pregnancy rate to be 14% to 24% -- that is, far higher than the ovulation rate. Because we do not see this clinically, we must ask why is the clinically measurable pregnancy rate far lower than the theoretical rate based on the rate of breakthrough ovulation? A number of explanations exist including the failure of sperm to reach the egg due to thicker cervical mucus or a change in motility within the fallopian tubes which OCP use may cause. But one must also recognize that the difference in rates may be due to a failure of the zygote/embryo to implant due to effects of OCP use on the endometrial lining. In short, the observation that "on-pill" pregnancy rates roughly parallel "on-pill" ovulation rates, serves, if anything, to give evidence in favor of the argument that the OCP acts as an abortifacient.

*The total pregnancy rate (detectable and non-detectable pregnancies) would be the total number of pregnancies per cycle in the average woman: 28% + (279/600 x 28%) = 41.0%.

2: They write:

"There is regular successful implantation of the invasive blastocyst on surfaces a great deal more 'hostile' than 'hostile endometrium' (eg, fallopian tube lining). 'Hostile endometrium' is not a demonstrated clinical reality."


It has already been stated in the answers to questions B-K that the sum of the evidence -- both recent and old -- supports the argument that OCPs change the lining of the endometrium in a fashion unfavorable for implantation. The fact that the unborn child may attach him or herself to a structure such as the fallopian tube lining has little to do with the previous arguments. Although one can make the argument that a rare occurrence or an exception disproves a theory, one cannot deduce the converse, namely, that the exception proves the theory. That is, noting that some unborn children do implant in the fallopian tube, or for that matter in the peritoneal cavity, merely proves that it is possible for this event to occur. But it offers no evidence that justifies the claim that a favorable implantation site is just as good as an unfavorable one.

3: They write:

"The extremely rare reporting of ectopic pregnancies associated with hormonal contraception would indicate the rarity of actual conception by patients using these modalities."


Once again these physicians apparently were unaware that their statement serves the purpose of supporting the action of OCPs as abortifacient. Women who take OCPs and those who do not, can and do become pregnant. The pregnancy can be an extrauterine pregnancy (EUP) (ie, usually a tubal pregnancy) or an intrauterine pregnancy (IUP) (ie, the normal type of pregnancy). One can measure the ratio of EUP to IUP in either group. What should happen to this ratio (ie, EUP/IUP) if one compares women who are not taking OCPs to those who are?

The Ob/Gyns would argue that this ratio should remain constant and if the reporting of ectopic pregnancy was 'practically unreported," as the Ob/Gyns wrote, one might even expect the ratio to decrease, because the numerator would become smaller. On the contrary, if OCP use caused more early abortions (ie, less intrauterine pregnancies), one would expect the number of intrauterine pregnancies (IUPs) to decrease in comparison to the number of extrauterine pregnancies (EUPs) and thus the ratio should increase. What does the literature say?

The studies to date note that women who take OCPs have an increased ratio of EUP to IUP. They note that women who take OCPs are far more likely to experience more EUP's per IUP than women who do not take OCPs, which supports the argument that the OCP acts as an abortifacient. The odds ratio (eg, an odds ratio of 2.0 is the same as saying a 2-fold risk) of the increased risk of EUP/ IUP in women taking OCPs compared to women who were not taking OCPs were as follows: 1) WHO 43  found an odds ratio of 1.7 (1.1-2.5); 2) Mol et al 44  found an odds ratio of 1.8 (0.9-3.4); 3) Job-Spira et al 45  found an odds ratio of 4.3 (1.5-12.6); 4) Thorburn et al 46  found an odds ratio of 4.5 (2.1-9.6); and 5) Coste et al 47  found an odds ratio of 13.9 (1.8-108.3). These clinical studies once again contain evidence which suggests that the OCP acts as an abortifacient.

In conclusion, the arguments presented by the 22 physicians in the booklet entitled Hormonal Contraceptives: Are they Abortifacients? lack substance and actually serve to bolster the evidence that use of oral contraceptive pills causes early abortions. (An excellent overview of the histologic and immunologic evidence is given in great detail by Larimore and Stanford in the February, 2000 edition of the Archives of Family Medicine 48.)

Next page: References »
1  2  3  4