Female Reproduction Contraception
Clinical background
There are many oral contraceptive
preparations on the market and a choice should be made to prescribe the one
with the lowest estrogen and progesterone concentrations that give good cycle control.
Combined oral contraceptives (COCs) can also be used to treat a number of
gynaecological conditions involving irregular cycles, menorrhagia or
dysmenorrhoea. In addition to progesterone only pills (POPs), intrauterine
devices which release progesterone locally to the endometrium are available
(Mirena Intrauterine Systems, Schering Health) and are used both for
contraception and for the treatment of endometriosis and other painful
disorders of menstruation.
COCs are contraindicated in women who
are pregnant, or who have a history of various forms of cardiovascular disease,
cerebrovascular problems, certain liver disorders and undiagnosed
gynaecological problems. COCs influence blood coagulation and there is a small
increased risk of deep vein thrombosis, pulmonary embolism, stroke and
myocardial infarction. This is slightly higher in women taking COCs containing
third-generation progestagens (desogestrel, gestodene), particularly when
there are other risk factors such as obesity, smoking and older age (>35
years). COCs should not be prescribed to women with known clotting
abnormalities or a history of hemiplegic migraine. Side-effects should be
monitored including regular blood pressure readings.
Oral contraceptives
Oral contraception is fertility control
using orally active synthetic sex hormone derivatives (Fig. 30a).
Combined oral contraceptives (COCs) represent the most widely used form of
estrogens and progestagens, and constitute the most reliable and effective
method for preventing pregnancy in countries where they are widely available.
COCs act by preventing ovulation through negative-feedback inhibition of
gonadotrophin release. Women taking COCs do not show the early follicular rise
of follicle-stimulating hormone (FSH), nor the midcycle rises in FSH and
luteinizing hormone (LH). The COC is taken daily for 21 days and withheld for
seven, to induce withdrawal bleeding. The COC may also act directly on the
uterus and cervix. Cervical mucus becomes more viscous, presumably inhibiting
penetration by sperm, and the endometrium does not develop into a suitable
matrix for implantation.
Sequential COCs are prescribed so that the user takes estrogen
alone daily for 14–16 days, then estrogen and progestagen together for 5–6
days, then 7 days without any pills; this aims to mimic the natural cycle.
Advantages of COC use. COCs provide reliable, reversible contraception
and have a number of other advantages such as reduced dysmenorrhoea and
menorrhagia, less benign breast disease and a reduced risk of ovarian and
endometrial cancer.
Disdvantages of COC use. There is a small increase in the rate of venous
thromboembolism in all women taking COCs and a history of thromboembolic
disease or other risk factors for thromboembolism, such as obesity, immobility
or a family history, are contraindications to this form of contraception.
Likewise, there is an increased risk of arterial vascular disease and the COC
should be avoided for older women, particularly smokers with obesity and/or
hypertension. Other relative contraindications include migraine and a number of
rare liver disorders. COCs should not be given to women with a history of
breast or genital tract cancer.
Progestagen only pills (POPs;
mini-pills) were introduced to
eliminate the adverse effects reported with estrogen use. The progestagen does
inhibit FSH and LH release but a major component of action is due to the
thickening of cervical mucus, and endometrial atrophy. The method is not as
reliable as COCs, the success rate being 97–98%, as opposed to 99% for
combination OC use. Adverse effects reported with progestagen only OCs are:
amenorrhoea; changes in plasma high-density lipoprotein (HDL) and low-density
lipoprotein (LDL) – HDL decrease and LDL increase in concentration in plasma;
breakthrough bleeding and ‘spotting’; and abnormal responses to glucose
tolerance tests.
Emergency contraception is prescribed as levonorgestrel and is effective
if the first dose is taken within 72 hours of unprotected intercourse. The
treatment creates an endometrial environment hostile to the blastocyst and is
followed by a withdrawal bleed that may be heavy.
Other uses of estrogens
Hormone replacement therapy (HRT) describes the use of sex hormones to replace the
lack of endogenous hormones resulting from the cessation of cyclicity of
ovarian function at the menopause or in women who have developed hypogonadism
for other reasons. HRT is administered in the form of sequential daily doses of
estrogen, coupled with progesterone in women with an intact uterus to prevent the
risk of endometrial hyperplasia and malignancy. There are numerous HRT
preparations in the form of tablets, transdermal patches and creams. The
benefit versus risk of HRT should be calculated in all symptomatic menopausal
women and it should not be prescribed for longer than 5–10 years, following
which the risks from breast cancer and cardiovascular disease increase. In the
absence of good data to the contrary, hypogonadal women should be treated up
until the expected age of the menopause.
