The term emergency contraception encompasses all methods of preventing unwanted pregnancy used after unprotected sex or when other methods of contraception have failed. This article outlines the most commonly used methods and their mechanism of action.
Table of contents:
- Contraception after intercourse
- Main mechanisms of action of hormonal postcoital contraception
- What to use in hormonal postcoital contraception
- Contraception after intercourse - contraindications
- Effectiveness of postcoital contraception
Contraception after intercourse
Postcoital contraception is a method of management aimed at preventing unwanted pregnancy resulting from unprotected intercourse or when other forms of contraception used have failed for various reasons.
It is a safe and, above all, highly effective method. It is commonly referred to as post-coital or emergency contraception. It includes any form of contraception used after intercourse to avoid pregnancy. Depending on the method used, emergency contraception is used between 2 and 7 days after intercourse. Its main mechanism is to prevent fertilisation or implantation of a fertilised ovum in the mucosa of the uterine cavity. This applies for a period of about 5 days after ovulation.
Any method used at a later stage, i.e. after implantation, is already classed as a form of early contraception and not postcoital contraception. The effectiveness of this method is greater the earlier it is used.
For centuries, an effective method of preventing pregnancy has been sought. One of the many methods used was to wash oneself after intercourse with fluids containing sperm-destroying substances. However, this did not produce satisfactory results due to the fact that approximately 90 seconds after ejaculation, fertilisable sperm can be found in the cervical mucus, which already reaches the fallopian tubes a few minutes after ejaculation. As can be seen from the above, all natural methods such as perineal flushing or vaginal irrigation performed after intercourse are not sufficiently effective and the risk of pregnancy is high.
Currently, two basic methods are used for contraception after intercourse. The first involves taking hormonal pills, while the second involves inserting an IUD.
The beginning of pregnancy is considered to be the implantation of the fertilised ovum in the mucous membrane of the uterine cavity, or so-called nidation or implantation, which occurs about seven days after fertilisation.
The main mechanisms of action of postcoital hormonal contraception:
- Blocking or delaying ovulation, depending on at which point in the menstrual cycle the drug is taken.
- Changes in the mucous membrane of the uterine cavity preventing the possible implantation of a fertilised ovum.
- Thickening of the cervical mucus causing an impediment to sperm migration.
- Disruption of the movement of the ovum in the fallopian tube and of the embryo.
For many years, increased doses of binary (oestrogen+progestogen) contraceptive pills were most commonly used for postcoital hormonal contraception, resulting in blocking ovulation (if the drugs were administered before the ejection of LH) or preventing the fertilised ovum from implanting in the endometrium. This regimen is called the Yuzpe method after the Canadian gynaecologist who first used it. However, it caused very troublesome side effects, so the search began for doses of hormones that, on the one hand, would not reduce the contraceptive effect, while on the other, minimising the side effects of their use.
Postcoital hormonal contraception uses:
- The binary contraceptive pill - rarely used.
- Progestogens - most commonly used.
- Danazol - used very rarely.
- Synthetic or conjugated oestrogens.
- Antiprogesterones - not used in Poland.
Binary contraceptive pills, used to prevent pregnancy after intercourse, should contain an adequate dose of two hormones: an oestrogen (EE-ethinylestradiol) and a progestogen (LG-levonorgestrel). The hormones used do not destroy the already implanted zygote and therefore it is not an early abortion method.
Although the Yuzpe method can still be used, at present the most popular method for postcoital contraception only is the progestogen-only pill (levonorgestrel). This method was only developed in the 1980s and is still being modified and improved. One of the advantages of this particular pill is that it can be taken by women with absolute contraindications to the use of oestrogens. This is because levonorgestrel itself does not cause any serious side effects.
Postcoital hormonal contraception can lead to dysfunctions of the hypothalamic-pituitary-ovarian system and the fallopian tubes, the uterus and particularly its mucous membrane. These disorders are the main cause of the appearance of various side effects. The most common side effects of the drug are nausea, vomiting, headaches and dizziness, breast pain and tenderness. Spotting, bleeding or disturbances in the regularity of previous menstrual cycles may also occur. The Yuzpe method should not be used more than once per cycle, while the levonorgestrel-only preparation should be used 4 times per cycle, as a single application of hormones after intercourse in a given cycle does not protect for the entire cycle.
Contraception after intercourse - contraindications
The short duration of action of hormonal drugs used for postcoital contraception means that there are relatively few contraindications to its use. In women with absolute contraindications to binary contraceptive pills, the Yuzpe method should be used with great caution. The main contraindications to postcoital contraception include, first and foremost, pregnancy, so it is advisable to carry out a pregnancy test before taking the pill to check whether a pregnancy has already occurred. Others include hypersensitivity to any component of the drug and acyclic undiagnosed reproductive tract bleeding.
After taking hormones, menstruation usually occurs on time or in the next 21 days. The later after ovulation the medication is taken, menstruation may appear later. If menstrual bleeding does not occur 21 days after taking the medication, you should see your doctor. Contraceptive pills must be prescribed by a doctor, as not all preparations can be used for postcoital contraception. This applies in particular to preparations containing third-generation progestogens such as norgestimate, desogestrel or gestogen.
The regimen of hormonal drugs for postcoital contraception depends on the preparation to be used. It depends on the type and doses of hormones contained in the tablets. In the Yuzpe method, 4 tablets of the classic contraceptive preparation are usually taken no later than 72h after intercourse. After 12h, another identical dose of tablets should be taken. Tablets containing only levonorgestrel (750 mg) should be taken up to 72 hours after intercourse in two doses, every 12h. It is best to take the first tablet in the first hour after intercourse, and the next one 12h after the first one. A preparation consisting of only 1 tablet containing 1500 mg levonorgestrel has recently been registered in Poland.
One basic principle of all the methods presented is that the shorter the time between intercourse and taking the tablet, the lower the risk of pregnancy. Taking the tablets after 72h is pointless. After this time, if fertilisation has occurred, the hormone they contain (synthetic progesterone) will only sustain the pregnancy that has been initiated.
If for some reason it is not possible to take the pill within 72 hours, an alternative is to insert the IUD up to 5 days after intercourse. However, it should be borne in mind that if implantation has already occurred, the IUD can act as an early abortifacient. The copper-containing IUD was first used for contraception after intercourse in 1970. To date, this method has not gained much popularity and is still used very rarely.
Effectiveness of contraception after intercourse
The efficacyof postcoital contraception is high, ranging from 75% (Yuzpe method) to 85% (progestogen method), but lower than traditional continuous hormonal contraception.
The use of an effective method after the fact of intercourse is in many cases a necessity, but it should be used in exceptional situations due to its side effects. This is most often the case where there has been rape, incest or unprotected sexual intercourse with minors or under-privileged women. Its use is also advisable when contraceptives have failed, or in the presence of serious illnesses in which pregnancy may pose a serious threat to the woman's health or even life.
This method should not be used as a primary means of regulating fertility, but only in emergency situations. In the event of frequent use of this form of contraception, it is worth considering other, more effective and safer forms of continuous pregnancy prevention.
