In considering options of which birth control method to use, couples have a variety of factors that they may consider. See prior discussion at Times & Seasons here.
Among the information that couples need are the medical facts about contraception, including effectiveness, side effects, and mechanism of action. Why is mechanism of action an important consideration?
Different birth control methods may act at different stages of the reproductive cycle. While most birth control methods act before fertilization, some birth control methods may also have secondary effects after fertilization to prevent a clinically recognized pregnancy (a secondary postfertilization effect). Such effects could include direct killing of the embryo, or creating an inhospitable uterine environment for implantation and maintenance of the pregnancy. While some authors have called this an abortifacient effect, other authors have objected that because pregnancy has been defined to begin at implantation (a new definition that is not universally accepted in medicine or science), an â€œabortionâ€? or â€œabortifacientâ€? effect can operate only after implantation. The term â€œpostfertilization effectâ€? identifies this issue of interrupting early human development unambiguously without eliciting controversy based purely on competing definitions of the beginning of pregnancy. Regarding the definition of pregnancy, see
National opinion polls suggest that many women (about half) believe that â€œhuman life beginsâ€? at fertilization regardless of whether pregnancy is defined by medical experts to begin at fertilization or implantation.
For these women, a birth control method that could act after fertilization may conflict with personal moral and religious beliefs. As a result, these women may wish to refrain from using birth control methods that may exhibit a postfertilization effect.
We have recently published a study showing that a large percentage of female patients in Utah and Oklahoma are concerned about this issue and make their choices of birth control methods in accordance with their beliefs about which methods do not have a postfertilization effect:
Which methods of birth control have postfertilization effects? Hereâ€™s where it gets a little bit fuzzy. Other than abortion (including very early medication-induced abortion or â€œmenstrual regulationâ€? with RU-486 or mifepristone or other drugs), there is probably no method of birth control that operates mainly through postfertilization effects. Oral contraceptives (â€œthe pillâ€?) prevent ovulation most but not all of the time. However, there is medical evidence (but not absolute proof) that oral contraceptives have a postfertilization effect at least some of the time. How often they work this way is completely unknown. Postfertilization effects are more likely for the progestin-only pill (the â€œmini-pillâ€?), or when â€œthe pillâ€? is not taken consistently, i.e., doses are missed. We have reviewed the evidence:
The intrauterine device (IUD) prevents sperm migration through the uterus most but not all of the time. There are data on fertilization rates in women with the IUD, such that estimates can be made as to how often an embryo that has been formed dies as a result of the presence of the IUD. This ranges from 0.2 to 2 embryo losses per woman wearing an IUD per year.
Emergency contraception (â€œthe morning after pillâ€?) prevents ovulation much but not all of the time. We estimate that when emergency contraception prevents clinically recognized pregnancy, it does so by a postfertilization effect somewhere between 10-50% of the time.
Only when women are educated about the mechanisms of action of birth control methods can they make a fully informed decision in the process of birth control selection. Informed consent can be explained as the right and ability of individuals to determine their own goals based on their own values and to decide how they will achieve these goals they have established. A woman should be provided such information to determine her own goals in choosing birth control methods that are in harmony with her own beliefs and values. Not providing available information concerning postfertilization effects to women who consider this information important is a violation of informed consent. If moral or religious beliefs relating to when human life begins in relation to postfertilization effects are important to some women, as our research has documented, then it is their right to make a decision whether or not to use a birth control method that may exhibit such effects. Without such information, patients are denied the opportunity to make an informed decision.