Table of Contents
Page created on June 7, 2021. Last updated on January 10, 2022 at 19:39
Definition
Hormonal contraception involves progestins with or without oestrogens to achieve contraception. There are many types:
- Daily-use contraception
- Combined oral contraceptive pills
- Progestin-only contraceptive pills (also called minipill)
- Nondaily-use contraception
- Contraceptive patch
- Vaginal ring
- Injectable progestin
- Subdermal progestin implant
- Hormonal IUD (topic A13)
Many types of oestrogens and progestins can be used in hormonal contraception:
- Oestrogens
- Ethinyl oestradiol
- Oestradiol valerate
- 17-beta oestradiol
- Progestins
- Norethindrone
- Desogestrel
- Levonorgestrel
- Cyproterone acetate
Efficacy of contraceptives may be measured by the Pearl index, which is the number of unwanted pregnancies per 100 woman-years.
Mechanism of action
Oestrogen-containing contraceptives works mainly by increasing the negative feedback on the hypothalamus and pituitary. This inhibits the release of FSH and LH, which inhibits ovulation and folliculogenesis.
Progestin-containing contraceptives work mainly by making the body think that it’s pregnant. This has the following effects:
- It makes the cervical mucous thicker and impair fallopian tube peristalsis, thereby inhibiting movement of sperm and implantation (main effect)
- It inhibits LH secretion, thereby inhibiting ovulation
- It inhibits endometrial proliferation, thereby preventing implantation
Combination contraceptives contain both oestrogen and progestin, thereby exerting the effects of both.
Side effects
Oestrogen-containing contraception has the following potential side effects:
- Headache
- Mood disorders
- Venous thromboembolism
- Cardiovascular events (AMI, stroke)
- Hepatic adenoma
- Increased risk of cervical cancer
Progestin-containing contraception has the following potential side effects:
- Breakthrough bleeding (mid-cycle bleeding)
- Follicular cyst
Contraindications
There are some people in which oestrogen-containing contraception is contraindicated. This includes those with:
- Previous thromboembolism
- Coagulopathy
- Atherosclerotic cardiovascular disease
- Liver tumours
- Breastfeeding
- Migraine
- Oestrogen-dependent tumours (breast cancer, endometrial cancer)
- Smoking, if also > 35 years
Combined oral contraceptive pills
- Pearl index with ideal use = 0,1
- Pearl index with typical use = 7
Combined oral contraceptive pills contain both oestrogen and progestin. They are generally the first choice for people who want contraceptive pills. However, they can not be used while breastfeeding (as the oestrogen stops the milk production).
One blister pack of combined contraceptive pills contain 21 pills which contain the active ingredients (oestrogen and progestin), and 7 inactive pills, or 24 active and 4 inactive. The inactive pills contain no active ingredients but are present to keep the patient in the rhythm of taking one pill per day. This 4 or 7 day hormone-free period allows bleeding to occur, due to the absence of hormones. Protection lasts during these hormone-free days as well.
This predictable, monthly bleeding is one advantage of combined oral contraceptive pills over progestin-only pills.
Indications other than contraception include:
- Hyperandrogenism
- PCOS
- Acne
- Menorrhagia and dysmenorrhoea
- Endometriosis
- Functional hypothalamic amenorrhoea
Combined oral contraceptive pills can be monophasic, biphasic, or triphasic. In monophasic pills, the dose of oestrogen and progestin is constant in all the active pills throughout the cycle. In biphasic and triphasic pills, the doses of the hormones vary across the cycle. There are no proven advantages to multiphasic pills over monophasic.
For the first seven days on the combined pill, the woman should use other prevention as well, like condoms.
The combined contraceptives have some other advantages as well. They:
- Protect against endometrial and ovarian cancer
- Protect against osteoporosis
- Make periods become regular and easy to predict
Progestin-only contraceptive pills
- Pearl index with ideal use = 0,3
- Pearl index with typical use = 7
Progestin-only contraceptive pills, sometimes called minipills, are generally used in those who desire oral contraption but who have contraindication to the combined pill. These pills can be used during breastfeeding.
The progestin-only pills avoid the oestrogen-mediated side effects of combined pills. However, they have a few disadvantages over the combined pills:
- The menstrual bleeding can be irregular and unpredictable, increased, or prolonged
- They also have slightly lower efficacy than the combined pills
- The pill must be taken at the same time every day
Unlike the combined contraceptive pills, the progestin-only blister pack contains no inactive pills.
Contraceptive patch
- Pearl index with ideal use = 0,3
- Pearl index with typical use = 7
Contraceptive patches are small transdermal patches containing oestrogens and progestins. One patch is worn for 1 week.
The patch is changed every week for 3 weeks, after which there is one week without a patch.
Vaginal ring
- Pearl index with ideal use = 0,3
- Pearl index with typical use = 7
The vaginal ring is a small soft plastic ring which is inserted into the vagina. It contains oestrogens and progestins. One ring is left in for 21 days, after which there is a 7-day ring-free break.
Injectable progestin
- Pearl index with ideal use = 0,2
- Pearl index with typical use = 4
The person is injected with a intramuscular injection of depot progestin. It releases progestin slowly and lasts for 12 weeks, depending on the type. Before the injection expires, the person must return for another injection.
One disadvantage of this is that it may take more than 1 year after stopping before normal fertility returns.
Subdermal progestin implant
- Pearl index with ideal use = 0,1
- Pearl index with typical use = 0,1
This is a small rod which is implanted subdermally on the upper arm of the patient. It releases progestin slowly and lasts for 3 years.