AAPLOG (1999). Embryocidal Effects of Contemporary Contraceptives: A Review.
AAPLOG. Embryocidal Effects of Contemporary Contraceptives: A Review. 1999.
AAPLOG. Embryocidal Effects of Contemporary Contraceptives: A Review. 1999.
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Abstract
The mechanism of action of contraceptive drugs and devices forms an essential part of informed consent for patients considering various methods of family planning. Currently the literature is confusing at best, in part due to non-uniform definitions of basic terms, as well as the misinterpretation of endpoints of current. AAPLOG members take different positions on the issue of contraception per se. The purpose of this document is to investigate and summarize the current evidence-based concerns regarding potential embryocidal mechanisms of action of modern contraceptive drugs and devices.
There are three reasons for concern about embryos conceived during the use of a particular contraceptive drug or device:
All contraceptive drugs and devices “fail” at a certain rate. As noted in a recent paper, “Unintended pregnancies occur with all contraceptive methods, including IUDs. This provides incontrovertible evidence that fertilization and implantation can occur, albeit rarely, with modern methods of contraception.”1
Since pregnancies can and do occur during the use of all contraceptive drugs and devices, then we know by definition that fertilization, which marks the beginning of an embryonic human organism, can and does happen with all contraceptive drugs and devices since by definition, an embryo must be created for pregnancy to occur. That means embryos are created at a certain rate with all contraceptive drugs or devices.
The contraceptive drug or device will create a certain environment for the embryos created during their use. This environment may adversely affect embryo survival up to the point of yielding a positive pregnancy test at the end of the cycle (the contraceptive efficacy end point).
The remainder of this article will try to summarize what is known in the published medical literature about the environment facing an embryo who has been created during the use of various kinds of contraceptive drugs or devices.
Buskmiller C et al., 2020·Linacre Q·Free full text on PubMed Central
This review sought to evaluate the evidence for embryo formation during intrauterine device (IUD) use, to articulate how often embryo loss occurs in well-designed studies, and to comment on other bodies of literature suggestive of postfertilization mechanisms of action of IUDs. The MEDLINE, EMBASE, and Ovid databases were searched for English-language studies of markers of pregnancy in IUD users in May 2018. Studies of human chorionic gonadotropin (hCG) were subjected to quality assessment based on the US Preventive Services Task Force quality tool. Bias of studies assessing pregnancy in other ways was assessed on a study-to-study basis. In all, 1,073 studies were identified and 138 were read in detail. Twenty-three studies of β-hCG, 4 studies of direct observation of embryos in fallopian tubes, 2 studies of pregnancy-specific binding globulin (PSBG), and 1 study of heat-shock protein 10 (Hsp10) or chaperonin 10 were included. In all studies considered together, 7.3 percent of IUD users had evidence of fertilization and pregnancy failure. In good-quality studies, 4.5 percent had evidence of fertilization and pregnancy failure. There are no randomized trials of embryo formation and loss in IUD users compared with noncontracepting controls. Studies of β-hCG span a large spectrum of quality, but several good-quality studies exist, which support embryo formation and loss in IUD users. Evidence of embryos found in tubes is moderate and evidence of PSBG and Hsp10 elaboration was limited, but these are also concerning for embryo formation and loss. There is good-quality evidence of embryo formation and loss in IUD users. Studies are inconsistent, and the stated conclusions of several papers inaccurately diminish postfertilization evidence of embryo formation. To better assess the rate of embryo loss in IUD users compared with non-users, future research should include well-designed prospective trials and less subjective assessments of embryos in fallopian tubes. A systematic review was carried out examining the English-language literature in the MEDLINE, EMBASE, and Ovid databases for evidence of embryo formation and loss during IUD use. In all, 1,073 studies were identified and 138 were read. There are no randomized trials and evidence ranges in quality, but evidence for the embryo formation and loss in 4.5 percent of IUD users exists in good-quality research. Further research is needed to compare embryo loss in IUD users to loss in controls.
There are many potential mechanisms of action for the intrauterine device (IUD), which vary by type of IUD (inert, copper, or hormonal). This paper reviews the evidence for each potential mechanism of action. On the basis of available data for fertilization rates and clinical pregnancy rates, the relative contribution of mechanisms acting before or after fertilization were quantitatively estimated. These estimates indicate that, although prefertilization effects are more prominent for the copper IUD, both prefertilization and postfertilization mechanisms of action contribute significantly to the effectiveness of all types of intrauterine devices.
The primary mechanism of oral contraceptives is to inhibit ovulation, but this mechanism is not always operative. When breakthrough ovulation occurs, then secondary mechanisms operate to prevent clinically recognized pregnancy. These secondary mechanisms may occur either before or after fertilization. Postfertilization effects would be problematic for some patients, who may desire information about this possibility. This article evaluates the available evidence for the postfertilization effects of oral contraceptives and concludes that good evidence exists to support the hypothesis that the effectiveness of oral contraceptives depends to some degree on postfertilization effects. However, there are insufficient data to quantitate the relative contribution of postfertilization effects. Despite the lack of quantitative data, the principles of informed consent suggest 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 oral contraceptives.