Combined oestrogen-progestogen oral contraceptives have been extensively used since 1956. The principal mechanism is inhibition of ovulation (4, above) through inhibition of gonadotrophin secretion from the hypothalamus. In addition the endometrium is altered, so that implantation is less likely (7, above) and cervical mucus becomes more viscous and impedes the passage of the spermatozoa (5, above).
8 The word 'pill' has gained currency in both professional and popular usage to mean 'oral contraceptive', losing its original precise technical pharmaceutical meaning.
Oestrogens alone are not completely reliable. At the necessary dose, they can also cause thromboembolism and endometrial cancer.
Progestogens used alone inhibit ovulation in up to 40% of cycles, render cervical mucus less easily penetrable by sperm and induce a premature secretory change in the endometrium so that implantation does not occur. There is liable to be break-through bleeding and some are a cause of raised blood pressure and an adverse trend in blood lipids and arterial disease.
An appropriate dose of oestrogen + progestogen gives excellent reliability with good menstrual cycle control. The following account applies to these combined preparations.
The combination is conveniently started on the first day of the cycle (first day of menstruation) and continued for 21 days (this is immediately effective, inhibiting the first ovulation). It is followed by a period of 7 days when no pill is taken, and during which bleeding usually occurs. Thereafter, regardless of bleeding, a new 21-day course is begun, and so on, i.e. active tablets are taken daily for 3 weeks out of 4.9 For easy compliance, some combined pills are packaged so that the woman takes one tablet every day without interruption (21 active then 7 dummy).
In some instances, the course is not started on the first day of menstruation but on the 2nd to the 5th day (to give a full month between the menses at the outset). An alternative method of contraception should then be used until the 7th pill has been taken, since the first ovulation may not have been suppressed in women who have short menstrual cycles.
9 Despite rigid adherence to it, women occasionally conceive on this regimen, i.e. their follicles develop early. Where this has occurred yet the women wishes to continue on hormonal contraception, a safer regimen is 24 days hormone administration with a 4-day interval.
10 It may also be prudent to tell the patient how the pill works: 'Her medical records showed that over the previous 3 months, she had received 6 months supply of a contraceptive pill. Had she lost some, or had someone else taken the pills? After a shy pause, she confided that she was taking two pills a day — one for her husband and one for her lover.' Lancet 2000 356:1118.
The pill should be taken about the same time (to within 12 hours) every day to establish a routine.10 The monthly bleeds that occur 1-2 days after the cessation of active hormone administration are hormone withdrawal bleeds not natural menstruation. They are not an essential feature of oral contraception, but women are accustomed to monthly bleeds and they provide monthly reassurance of the absence of pregnancy.
Numerous field trials have shown that pro-gestogen-oestrogen combinations, if taken precisely as directed, are the most reliable reversible contraceptive known. (The only close competitors are depot progestogens and progestogen-releasing intrauterine devices.)
Was this article helpful?
Stop Your Scalp From Snowing! Finally... A Real Cure for Dandruff! No medication! No weird cures! No messy creams, smelly solutions or strange diets! Are you sick to death of being sold products that could make the problem worse? Are you sick of the shampoos and conditioners that make your head smell like sulphur? If so then try a permanent revolutionary treatment for dandruff!