“Emergency” contraception
“The expressions ‘emergency contraception’, ‘preimplantatory contraception’, ‘post-coital contraception’ are synonyms used to designate a range of practises used immediately after sexual relations which could have been fertilizing, in order to prevent a potential, unplanned, pregnancy. It consists in taking drugs (‘morning-after pill’) or using an intra-uterine device after sexual intercourse in order to prevent fertilization or, should fertilization already have occurred, to prevent the implantation of the embryo resulting from this conception”.
“The practise of post-coital birth control methods consists in the oral intake of a combination of female synthetic hormones (oestro-progestogenic) in heavy doses, ethinylestradiol and levonogestrel, or of a synthetic progestogen only (levonorgestrel) or of Danazol. The insertion of a copper treated intra-uterine device or the intake of Mifepristone (RU 486) immediately after intercourse are also considered as emergency contraception.
“These agents or devices work in different ways to interfere with the complex and delicate process of the implantation of a human embryo in the uterine endometrium, leading to the loss of this embryo”.
The “morning-after pill”: “a pill containing a heavy dose of hormones (progestin-only: Lenorgestrel, NorLevo), taken 72 hours after potentially fertilizing sexual relations in order to make them non-fertilizing (contraceptive effect) or to prevent the implantation of an embryo that has already formed (abortive effect). The operational mechanism of this pill depends on the moment of the menstrual cycle when sexual intercourse has taken place (this determines whether or not fertilization has occurred) and on the moment of the same menstrual cycle when the pill has been administered (before or after ovulation). If intercourse has taken place before ovulation, and if the morning-after pill has also been taken before ovulation, the pill’s effect is merely contraceptive. Nevertheless, the contraceptive effect of the pill ceases shortly before ovulation, giving way to an interceptive effect. If intercourse has happened shortly before ovulation or just after (making fertilization possible), and if the pill has been taken during this same period of time, it will act by preventing the already formed embryo’s implantation in the uterus (interceptive mechanism) and its effect is abortive. If the pill is taken when the embryo is already implanted, it has no effect”.
Intra-uterine devices: “the insertion of a copper treated intra-uterine device, the day after sexual intercourse, is a very efficient method (almost 100%) to stop a pregnancy from developing. Its efficacy is due to its ability to prevent the implantation of the embryo through a combination of mechanical, toxic (copper) and infectious (endometritis) effects. It is because of its abortive effect in preventing the nidation of an embryo that the IUD is such an efficient post-coital contraceptive. However, it is not recommended to insert an IUD under such conditions, as it can have unpleasant collateral effects, including uterine cramps, metrorrhagia and, especially, a significant risk of pelvic infection, if the intercourse took place with a little known partner, in the context of sexual promiscuity”.
Danazol: “progestogen agent, which no longer belongs to the commonly used emergency contraception methods, because of its high failure rate”.
Mifepristone (RU 486, “mifegyne”): “generally used to provoke an early abortion, it is also offered as emergency contraception. If administered in the very early stages of a pregnancy, it probably brings about an alteration of the endometrium’s structure, making the embryo’s implantation impossible. However, it is used as ‘emergency contraception’ only exceptionally, as it is more costly than Norlevo, requires a medical prescription and more often than not acts as a real abortifacient, causing the loss of the already implanted embryo (contragestion)”.
In conclusion:
- “emergency contraception does not always prevent ovulation, even when it is used before the ovulatory phase. The ‘contraceptive’ effect of these methods seems to be secondary at most, and certainly cannot explain the effectiveness of these products when administered after a possible fertilization”.
- “the main effect of these methods takes place after fertilization, perhaps at the molecular level, by disrupting the signal system (embryo-mother dialogue) that is necessary to prepare for implantation”.
- “we can therefore state that when ‘emergency contraception’ prevents a pregnancy from developing, it usually does so by preventing the implantation of an embryo that has already been conceived. It is therefore a pre-implantatory, and often abortive, pregnancy prevention method”.