Emergency contraception

Emergency contraception (EC) is defined as the use of any drug or device after unprotected intercourse to prevent an unintended pregnancy. It is an ‘after-sex’ or ‘back-up’ contraception solution.  It is also commonly known as ‘morning-after pill’ or ‘day-after pill’.

Emergency contraception can best prevent pregnancies when used soon (within 24h) after intercourse. It provides an important back-up in cases of unprotected intercourse or contraceptive accident and also after forced sex.  

Unprotected sexual intercourse can result from a couple not using any contraception, including ‘withdrawal’. It can also happen when they consciously try to prevent it. For example UPSI can happen as a result of accidental condom problem (breakage, slippage, not on in time); oral contraceptive (OC) problems e.g. forgotten pill; a temporary break from the usual contraceptive; forgetting to apply a patch or insert a vaginal ring. UPSI can also happen as a result of non consensual intercourse (rape).

Unprotected sexual intercourse (UPSI) is quite common. Approximately 30% sexually active women  aged 16.45 report having at least one unprotected sex in the last 12 months. These frequent acts of unprotected sexual intercourse are not happening in a distinct sub-population, but happen irrespective of age, income, education level and marital status.

Following UPSI, emergency contraception can help women to reduce risk of getting pregnant. Although the risk of pregnancy exists most of the time, women may underestimate the risk of pregnancy. Not recognizing pregnancy risk may be the most important barrier to EC use. A study has demonstrated that 61% of women terminating unplanned pregnancy in artificial abortion were not at all aware of the pregnancy risk - they didn't know that they have had unprotected, "risky" sexual intercourse.

Among those biomedical fields in which a virtual explosion of new knowledge and understanding has occurred over the past decades, the physiology and pathophysiology of reproductive processes are prime examples. It is of the utmost importance to transfer new knowledge towards general population in order to improve their reproductive health competencies and to achieve more favourable population outcomes.

Menstrual cycle theory
The follicular phase starts on the first day of menstruation and ends with ovulation. Prompted by the hypothalamus, the pituitary gland releases follicle stimulating hormone (FSH). This hormone stimulates the ovary to produce several follicles (tiny nodules or cysts), on the surface. Each follicle houses an immature egg. Usually, only one follicle will deliver an egg, while the others die. The growth of the follicles stimulates the endometrium to thicken in preparation for possible pregnancy.

The ovulatory phase relates to ovulation - the release of a mature egg from the ovary’s surface in response to rising levels of luteinising hormone (LH) and FSH. When the LH reaches a peak it triggers the rupture of the developing follicle to release the mature egg: ovulation; with no LH surge, ovulation does not occur. The released egg is funnelled into the fallopian tube and towards the uterus by waves of small, hair-like projections. The life span of the typical egg is only around 24 hours. Unless it meets a sperm during this time, it will die.

The luteal phase follows the release of the ovum, when ruptured follicle stays on the surface of the ovary. The follicle transforms into a structure known as the corpus luteum, which releases progesterone and small amounts of oestrogen. The thickened lining of the uterus is maintained and waits for a fertilised ovum to implant. If this happens the implanted ovum will start to produce human chorionic gonadotropin, detectable in a urine test for pregnancy. If pregnancy doesn’t happen, the corpus luteum regresses, usually around day 22 in a 28-day cycle. The drop in progesterone levels causes the endometrium to break down and menstruation begins again.

Current evidence challenges the simplified ‘text book’ understanding of the fertile window and overall menstrual cycle: we know today that only about 12% of ovulations happen on day 14 of the menstrual cycle. The variability of ovulation is large – it can happen from day 11 to day 21 in women with regular cycles.  In women with irregular cycles, it is even harder to predict. Furthermore, ovulation also varies from cycle to cycle.

Having in mind the variability of the ovulation and 5 days sperm survival following UPSI, it can be concluded that there are no risk free days of the cycle.

Dispelling key myths about oral emergency contraception

  1. Several studies have shown that facilitating access to EHC does NOT increase sexual or contraceptive risk-taking behaviour.
  2. A number of studies show that women and adolescents with greater access to EC are NOT more likely to engage in unprotected intercourse, and are more likely to adopt an ongoing contraceptive method after EHC use.
  3. Use of EHCs has NO effect on future fertility.
  4. If a woman is already pregnant, it is too late for EC. Emergency contraception does NOT interrupt an existing pregnancy or harm a developing embryo.
  5. EHCs do NOT protect against STIs. Only condoms protect against sexually transmitted infections.
  6. EHCs do NOT provide contraceptive cover for unprotected intercourse in the days following intake.

Which days of the cycle are fertile?

Sperm can survive for approximately 5 days within the female reproductive tract, which means that during the average woman’s menstrual cycle there are six days when intercourse can result in pregnancy. This ‘fertile window’ is the five days before ovulation plus the day of ovulation. However, since ovulation is highly unpredictable, it is very difficult to say which days of the cycle are fertile.

This means that the risk of pregnancy exists most of the time. However, women may underestimate the risk of pregnancy and miss the opportunity to prevent unplanned pregnancy. The lack of awareness of pregnancy risk may be the most important barrier to EC use.

The highest risk of pregnancy is when ovulation happens shortly after UPSI.  Sperm viability declines over time. This means that the risk of conception is highest during the first three days following unprotected sex or contraceptive failure.

Therefore, to avoid unwanted pregnancy, it is critical to avoid ovulation (happening shortly after UPSI while the sperm is still viable) by using EC as soon as possible.

The variability of ovulation is large: only 12% of women ovulate on the day 14. of the menstrual cycle. Ovulation can happen from day 11 to day 21.  If the cycle is not regular, there is a risk of ovulation happening even later in the cycle. Ovulation also varies from cycle to cycle.

Because sperm stay viable for up to 5 days, the period over which conception is likely to occur runs from day 6 to day 21 for regularly cycling women. The conception risk period does not end before day 28 for women with irregular cycles.  This shows that there is no such thing as a risk free period.

Having in mind large variability of the ovulation, it is clear why women who are not ready to get pregnant need to take EC following any UPSI, regardless of the day of their menstrual cycle.

In an everyday life it is very difficult to determine whether an unprotected sexual intercourse has happened during the fertile or non-fertile phase of the cycle, because of the ovulation being unpredictable and sperms surviving 5 days following UPSI in female reproductive organs.

Therefore all women who want to avoid getting pregnant following UPSI, need to take emergency contraception - regardless of the day of the menstrual cycle.


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