Abortion and the Pill

John B. Shea
July 7, 2000
Reproduced with Permission

Most people assume that the common oral contraceptive pill acts only as a contraceptive and that it does not cause abortion. A recent medical article in the Archives of Family Medicine shows that this assumption is incorrect.1 The authors studied much of the medical literature since 1970 that discussed most of the types of oral contraceptives, OCs, low dose phasic combined COCs (which contain estrogen and progestin), and progestin only pills, POPs.

How the Pill Acts

The mechanisms involved are:

The organs affected are:

Does the Pill Always Prevent Ovulation?

There is strong evidence that the OC does not always prevent ovulation and, that as a result, so-called 'break through' or 'escape' ovulation occurs. Conception sometimes does occur despite the use of OCs. The pregnancy rates following 'break through' ovulation are often underestimated.2 How often does 'break through' ovulation occur in women on OCs? For COCs, the rate ranged from l.7% to 28.6% per cycle.3 For POPs it ranged from 33% to 65%.4 In one study the ovulation varied from14% to 84%.5

Pregnancy Rates in OC Users

A study accounting for under-reporting of elective abortions gave these figures:

The rates are higher for POP users.

How the Pill Acts After Conception - The Evidence

It is a reasonable assumption that after conception, the pill can cause the death of the embryo (fertilized ovum) prior to or during implantation (the nesting of the embryo in the wall of the uterine cavity). No method has, as yet, been used to measure directly the rate of this embryo death prior to, or up to, the time of implantation. This could theoretically be achieved by the assay of certain pregnancy related hormones, but such studies have never been done on women using OCs.

There are, however, three lines of indirect evidence that strongly suggest that abortion of the embryo caused by the OC occurs in at least some women taking OCs.

1) The significance of the ratio of ectopic (tubal) pregnancies to intra-uterine pregnancies in women using OCs: If it were true that the only actions of the pill were impairment of ovulation and alteration of the cervical mucus, then OCs should reduce the rate of tubal pregnancies to the same extent as they reduce the rate of intra-uterine pregnancies. But all of the published data used by Larimore and Stanford, in their article published in the Archives of Family Medicine, and other authors, indicate that significantly more ectopic pregnancies, relative to intra-uterine pregnancies, occur in women who use OCs.7,8,9,10,11 This constitutes good evidence that OC use seems to be associated with risk of ectopic pregnancy or unrecognized loss of embryos from the uterine cavity. In one publication12 the authors assumed that in a woman who is taking OCs, and who has break-through ovulation, it is "highly probable" that the endometrium is primed and ready for implantation, simply because ovulation has not been suppressed. Yet, no one has studied the tissue characteristics (histology) of the endometrium at the time of implantation in women using OCs. The authors provide no direct or indirect evidence to support their assumption. If this assumption were true, some women should experience a normal cycle (in terms of menstrual flow) as she would if she were not taking the pill. This has never been described in the medical literature.

2) The effect of OCs on the endometrium: the endometrium is thinned  up to 58% thinner than normal. Its glands are fewer and are atrophied. Its cell structure is altered. Its biochemical composition is altered.13 Thinness of the endometrium is related to its functional receptivity, and when it becomes too thin, implantation does not occur.14 The average thickness of the endometrium in women taking OCs is 1.1mm. The minimal endometrial thickness required to maintain a pregnancy in patients undergoing in vitro fertilization ranges from 5 to 13mm. This is strong evidence that changes in the endometrium reduce the likelihood of implantation.15 The Food and Drug Administration (USA) has accepted the assumption that OCs render the endometrium inhospitable to the implantation of the embryo.

3) Integrins: These are a group of 'cell-adhesion' peptide molecules which are accepted as the markers of the receptivity of the endometrium for implantation and normal fertility. They are conspicuously absent in patients with unexplained infertility.16 Three of these integrins have been shown to appear locally in the uterus for a brief interval at the precise time in the menstrual cycle that corresponds to the window of maximal uterine receptivity to successful implantation. They are also conspicuously changed in OC users, and this fact is believed to contribute to the failure of implantation.17

To sum up, it can be reasonably stated that OCs can not only prevent ovulation and therefore conception, but also can, at least some of the time, cause an embryo, which was conceived despite the fact that the mother had been taking OCs, to be aborted, due to a failure of implantation. Further, OCs can cause an embryo to implant in the fallopian tube, which almost invariably results in death of the embryo, and sometimes death of the mother. These facts are recorded in the Physicians' Desk Reference, in Drug Facts and Comparisons and in most standard gynecological, family practice, nursing, and public health text books. Nonetheless, few physicians and patients are aware of them.

It is important also to realize that the abortifacient potential of OCs is magnified by the concomitant use of certain antibiotics and anti-convulsants which decrease the ovulation suppression effectiveness of the OCs. These drugs include barbiturates, anti-depressants, and virtually all classes of anti-biotics. Anti-biotic use among OC users is not uncommon, such women being more susceptible to bacterial, yeast, and fungus infections, secondary to OC use.

Failure on the part of the physician to provide the patient with information about the potential of OCs to produce abortion and ectopic pregnancy in a failure to provide complete informed consent. Nonetheless, many physicians have consistently tried to conceal these facts by arguing that …

The Catholic Church teaches that the practice of contraception is seriously sinful. The fact that it is probable that OCs are, at least sometimes, abortifacient, adds another seriously sinful aspect to their use. What are the implications of these facts for the regulation of births? The Catechism of the Catholic Church teaches that one aspect of parents' duty to fulfill their responsibility to transmit human life and to educate their children, concerns the regulation of births. Parents may wish to space the births of their children in a spirit of generosity appropriate to responsible parenthood, but not for selfish or ungenerous reasons. To achieve this goal, methods of birth regulation based on self observation and the use of fertile periods may be used, because they are in conformity with the objective criteria of morality. These methods respect the bodies of the spouses, encourage tenderness between them, and favour the education of an authentic freedom.18

Dr. Thomas Hilgers founded the Pope Paul Vl Institute for the study of human reproduction in Omaha, Nebraska (affiliated with Creighton University). He was appointed by Pope John Paul II to the Pontifical Council for the Family. He is also a member of the Pontifical Academy of Science. He and his colleagues have developed a new scientific approach to human fertility, called Natural Procreative Technology. It provides for procreative health care as well as responsible parenthood, and instructs couples on how to achieve, as well as avoid, pregnancy. It also has the potential for preventing uterine, ovarian, and breast cancer. Dr. Hilgers has suggested that the term 'natural family planning', which has negative connotations, be replaced by the term 'fertility care', a totally new approach to fertility. A textbook on this new reproductive science is in preparation at the Pope Paul Vl Institute. More information about 'fertility care' can be obtained from the Marguerite Bourgeoys Family Center, Fertility Care Programme in Toronto.


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