The Menstrual Cycle
Every month, one egg leaves one of the ovaries on its way to the uterus via the fallopian tubes. Meanwhile, in preparation for the egg to arrive, the uterus starts to develop a thicker lining and it’s walls become cushiony (the endometrial lining). If the egg reaches the uterus and is fertilized by a sperm cell, it attaches to this cushiony wall.
Most of the time the egg just passes right through without fertilization. Since the uterus no longer needs the extra blood and tissue which made up the walls thick, it sheds them by way of the vagina. This cycle will happen nearly every month until the ovaries stop releasing eggs, usually several decades later.(menopause). In the Ovarian Cycle diagram is clearly visible how the estrogen and progesterone are peaking during the regular cycle.
How it works
The most important mechanism of action of the pill is suppression of ovulation.
This effect is brought about by the sex hormones estrogen and progesterone in the pill. The hormones signal the brain that no further hormone production is necessary. The brain consequently steps down production of FSH (follicle-stimulating hormone). This largely inhibits the growth of the follicles and the production of estrogen by the body. As a result of the constant estrogen levels in the blood provided by the pill, the brain does not receive its mid-cycle signal to secrete large amounts of LH, the hormone which triggers ovulation. Without ovulation there is no mature egg available for fertilization and conception cannot take place.
The pill has two further effects which help to prevent conception:
It suppresses the development of the endometrium. This remains thin and has a texture that does not allow an ovum to implant. In addition, the progestin in the pill causes the cervical mucus to remain thick and impervious to sperm.
The Pill and ‘Periods’
The pill tricks the body into believing it is pregnant. When the pill was being developed, however, it was felt that women would find the lack of a normal menstrual cycle disconcerting. Many women rely on their regular menstrual period for reassurance of not being pregnant. Consequently, it was decided to have the pill consist of 21 days of active pills followed by a pill-free interval of seven days (either no pills or sugar pills for the 28 pack). The rapid decline in the hormone level results in a ‘withdrawal bleed’, which somewhat resembles a menstrual period and is often still referred to as a ‘period’ for simplicity. It is however important to understand that the bleeding which occurs during the pill free interval is not a menstrual period.
The pill free interval is the ‘Achilles heel’ of the pill’s efficacy, as it can contribute to pill failure. To stop ovulation from occurring a woman needs to take seven consecutive active pills. The lengthening of the pill free interval is one of the most common causes of pill failure and is often associated with a woman starting her new pill packet late or neglecting the last days since “the period” is about to come anyway. This may also occur if some of the active pills near the end of the previous packet or active pills near the start of the new packet are not absorbed properly (due to vomiting, diarrhoea, use of antibiotics) this can also mean that there has not been enough pills taken overall to prevent ovulation, especially with the lower dose pills that have become more common.
So why have a pill free interval? As discussed above, the pill free interval was devised in the early days of the pill because it was felt that women would find having a ‘period’ more acceptable. For a range of reasons, however, women may choose to tricycle their pill (taking three packets together without a pill free interval), thus reducing the number of withdrawal bleeds a year from 12 to four. The pill Seasonale is marketed for this reason while it in fact consists of 4 strips of microgynon 21. A shortened pill free interval could mean the hormones in the pill could be lower, therefore, reducing risks and side effects. Pills consisting of 24 days of active pills and a four day pill-free interval are currently available (mircelle, yaz). They contain only 15 micrograms of estrogen, this dosage is also used for the first full year pill.
Answers to other common myths surrounding the pill
The pill makes you fat
Not necessarily: When the pill was first introduced it contained much higher levels of hormones than what is available in the formulations today (100-175 micrograms of estrogen compared to 20-50 micrograms today). While weight gain was associated with these older high dose pills, the pill formulations used today do not always result in weight gain. It is estimated that in the first year of use:
• 20-25% of women gain more than 2kg/4.4lbs
• 60% of women experience no change or have a weight change within 2kg (both up and down)
15-20% of women actually lose more than 2kg weight .
The progestogen in the pill can increase appetite which may result in weight gain. Some women may also experience water retention but this can often be reduced by switching to a lower dose pill. The low-dose pill, Yasmin, is effective at reducing the symptoms of water retention.
You need to have regular breaks from the pill
False: This is one of the most commonly held beliefs about the pill, even by some health professionals. The idea of taking a break from the pill may have its origins in the fact that the older pills consisted of high hormone doses. Some people also think it is necessary to have a break from the pill to maintain fertility levels. Repeated restarting might be more harmful than the relatively steady-state situation that is maintained during sustained use. In addition, as side effects usually occur in the first few months of the pill’s use, often subsiding after a time, women restarting the pill may experience these side effects again. It may be useful for women to remember that they are actually ‘taking a break’ during the pill free period.
The most dangerous time to miss a pill is in the middle of the packet?
False: This myth seems to have come from the idea that ovulation occurs in the middle of a woman’s menstrual cycle. When a woman has been taking active pills her ovaries will be in a resting state (ovulation cannot occur). She can miss seven active pills without the risk of ovulation (which is what occurs in the pill free interval). Therefore, the least dangerous time for a woman to miss pills is in the middle of the packet and the most dangerous time is at the beginning or end of a packet.
The pill makes you infertile
False: This myth may stem from the fact that women using the pill as a form of contraception may delay childbearing until their late 30s, a time when their natural fertility has declined. It may take a few months for cycles to return to normal for women who were on the pill. It could actually be argued that being on the pill actually contributes to the preservation of women’s fertility as it reduces the incidence of a number of conditions which impact on fertility (eg. ectopic pregnancies, endometriosis, fibroids).
The pill causes cancer
Not necessarily: The pill actually provides a protective effect from cancer of the ovaries and cancer of the endometrium (the lining of the uterus). Women who take the combined oral contraceptive pill show an increased risk of cervical cancer. It has been suggested that women who use the oral contraceptive pill may be less likely to use condoms with new sexual partners and, therefore, can be more at risk of being exposed to STD’s specifically the HP virus (which is considered to be the main contributing factor to cervical cancer). A review of data on the pill’s use and breast cancer found there was a small increased risk of breast cancer in pill users, but this increased risk decreased after stopping use and after 10 years of discontinuation it had disappeared altogether.
The Morning After Pill
Recently the USA has followed the example of most European Countries by accepting the sale of the morning after pill without prescription. This is valid for the progesterone only pill containing of 1.5mg levonorgestrel in 1 or 2 pills. It has the suitable name Plan B in the US, referring to the fact it should not be used as regular birth control. It is only effective if taken within 72 hours of the unprotected intercourse. It is not effective when you are pregnant. It decreases the chance of getting pregnant by 89% — from 25% without, to 3% with the MAP if taken around time of ovulation. It is locally available under the name Postinor by prescription or discretion of the pharmacist.
Hormonal birth control should be mandatory education to keep the world’s population at bay.