The way women have been advised to take the combined contraceptive pill for the last 60 years unnecessarily increases the likelihood of taking it wrongly, leaving them unplanned pregnancy.
And this is the ideal situation for the result of a cosmetic quirk of tablet design, based on long redundant historical context.
This is because standard combined oral contraceptive pills – such as Microgynon, Rigevidon or Marvelon – are designed to be taken for 21 days, followed by a seven-day break, during which time the woman does not take the pill and experiences of the vaginal bleeding. Pill-taking women, therefore, have a "period" every month.
But this "period" is far from necessary. Shortly before his death in 2015 I attended a lecture given by Carl Djerassi, the "father of the pill".
He commented that the seven-day break, and consequent withdrawal bleed, was designed in the pill in the 50s in an attempt to persuade the Vatican to accept the new form of contraception, as an extension of the natural menstrual cycle.
As is well known, this did not succeed: Pope Paul VI forbade artificial contraception. Despite this, the seven-day break is a component of the combined oral contraceptive pill.
This is a problem The seven-day break is a hazard that may increase the risk of pregnancy while taking the pill.
This is because the level of contraceptive hormones in the body is the crucial factor in turning off ovulation, without which pregnancy can not occur. It takes approximately seven daily doses of contraceptive pill to reach the ovaries off.
But the seven-day break If pill-taking is not resumed by the ninth day after stopping, ovulation will occur.
Missing an occasional pill is unlikely to cause hormone levels to reduce the level of ovulation.
But taking a deliberate seven-day break lowers hormone levels to a point after which more missed pills, either before or after the break, may allow ovulation to happen.
The seven-day break is an inbuilt hazard. Many women accidentally prolong their pill free week by forgetting to restart the next packet on time, or by missing pills in the first or last week of the packet.
The reduction of hormones in these circumstances can lead to an unexpected ovulation, and, if intercourse has taken place, to pregnancy.
But by shortening the pill-free interval (from seven to four days) and decreasing the number of times a year, the woman is prompted to have a pill-free interval, the risk of accidental ovulation, and hence the unwanted pregnancy is reduced.
New patterns of tablet taking
As a result, many clinicians now have extended or continuous pill exercises where three or more packets of pill is taken consecutively and only then does a woman have a pill-free week, or a shortened pill free interval of four days.
Unhealthy overgrowth of the tissue (endometrial hyperplasia), which causes the cause of uncontrollable overgrowth of the tissue (endometrial hyperplasia).
They also prevent inconvenient "breakthrough" bleeding which eventually occurs if the lining is not allowed to shed.
Some women already "tri-cycle" 30 microgram (standard dose) or 20 microgram (low-dose) pills in this way, running two or three packets together before taking a break, often to reduce the side effects of hormone withdrawal, such as migraines .
But for more expanded continuous pill-taking, use of lower-dose pills containing 20 micrograms of oestrogen is recommended to offset the increased yearly dose of oestrogen when fewer breaks are taken. This is because the total dose of oestrous over is associated with the small, but well known, increased risk of breast cancer.
Using established contraceptive pills in this way is "off licence", meaning that the prescriber, not the manufacturer, will bear legal responsibility for their use.
Nonetheless, the expanded or continuous tablet use, off licence, is professionally acceptable, and newer pills are being developed and licensed by pharmaceutical companies, which are meant to be taken in a limited way, with fewer pill-free intervals.
Light or absent bleeding
As well as providing fewer opportunities for ovulation to occur, these extended regimens also mean that a woman has lesser bleeding days. One review found such regimens to be both safe and effective.
But many women express concern that no bleeding is possible for their health or fertility. Beliefs that menstrual blood "builds up inside" if bleeding does not occur or that the body needs to "cleanse" itself every month
This may be due to a misunderstanding about why bleeding does not occur
In a natural menstrual cycle, the lining of the womb builds up over the first half of the menstrual cycle under the influence of oestrogen, its peak thickness at the time of ovulation.
It is then maintained for 14 days by progesterone, after which, if no pregnancy occurs, it is shed through the vessels in the womb's lining, and the woman experiences a period.
In most contraceptive methods, which cause a lack of vaginal bleeding, the supply of continuous low-dose progesterone greatly reduces the thickening of the lining, so that there is no need for it shed.
In continuous long-acting methods like the IUS or contraceptive injection, women experience greatly reduced or no bleeding because the lining is largely dormant. With the combined oral contraceptive pill, lighter bleeding is experienced because the thinner lining sheds as a result of withdrawal of hormones, not because of a need to shed a proliferated lining.
Many women and girls welcome the reduction in bleeding days and the lessening of social disruption, and missed school and work days. With the increased recognition of "period poverty" and the women suffering from problems in the women's home during pregnancy.
Ultimately, the decision to bleed or not to bleed should be done, according to their lifestyle needs.
Cleaving to a 21/7 pattern of pill taking, which was instituted for social not medical reasons, on the grounds of either tradition or unfounded health concerns, contraceptive pills in respect to the default position.
This article was first published on The Conversation.