27
Contraception
Introduction
Over the last 70 years, the global population has tripled from 2 billion to over 6 billion. According to the median variation of the United Nations’ Review of World Population Prospects, 2010, the world population is expected to increase from 6.9 billion in 2011 to 9.3 billion in 2050 and to reach 10.1 billion by 2100. The current ‘ecological footprint’, the productive area of earth necessary to support the lifestyle of an individual, is approximately double the level that is sustainable long term. Many of the world’s population already does not have enough food to eat, the number of people experiencing water shortages is continuing to rise and is estimated to reach between 500 million and 3 billion by 2050. Widely available, effective contraception has a central role to play in limiting population expansion.
Contraception also has the potential to make a contribution to maternal and child survival. It has been estimated that family planning could save the lives of 3 million children a year by helping women to space births at least 2 years apart, and to bear children during their healthiest reproductive years. When women have the ability to space their births, they are better able to recover from nutritional depletion, blood loss and reproductive-system damage, allowing them to have healthier babies. Many women in the developing world would like to space or limit their births, but do not have access to family planning information or services.
Reproductive health programmes aid in the prevention of HIV transmission and other sexually transmitted diseases. Half of all new HIV infections in the developing world are among women and nearly 10% are among infants and children.
The provision of appropriate contraception is arguably one of the most important branches of medicine today worldwide. In the UK, it is estimated that for every £1 spent on contraception, £14 is saved for the NHS. A wide variety of effective contraceptive methods are available, but there is no ‘ideal’ contraceptive and choice must be based on the balance of risks and benefits of each method for each individual. For most women, the use of contraception is safe, but there are limited data on the use of contraception by women with certain medical conditions. In view of this, the World Health Organization (WHO) developed Medical Eligibility Criteria, which provide evidence-based recommendations to facilitate the safe use of contraception without imposing unnecessary medical restrictions. A UK version is available (www.fsrh.org.uk) and the categories used to define risk are summarized in Table 27.1.
Table 27.1
UKMEC categories
| UKMEC category | Definition |
| UKMEC 1 | A condition for which there is no restriction for the use of the contraceptive method |
| UKMEC 2 | A condition for which the advantages of using the method generally outweigh the theoretical or proven risks |
| UKMEC 3 | A condition where the theoretical or proven risks usually outweigh the advantages of using the methoda |
| UKMEC 4 | A condition which represents an unacceptable health risk if the contraceptive method is used |
a The provision of a method to a woman with a condition given a UKMEC category 3 requires expert clinical judgement and/or referral to a specialist contraceptive provider, since use of the method is not usually recommended unless other methods are not available or not acceptable.
Defining ‘contraceptive failure’ is not easy, as it depends on the population studied: studies on a young population will suggest a higher failure rate than in an older group, as fertility is higher in younger people. Caution is therefore required when interpreting relevant figures. The ‘method’ failure includes the inherent risk of failure providing the method is used correctly. It is quantified in the units per 100 woman-years (HWY), the number of women who would become pregnant if 100 of them used that method of contraception for 1 year. ‘User’ failure is the failure rates when the method is not used correctly (e.g. missed pills, late injections, drug interactions). If used consistently and correctly, hormonal contraceptives (combined hormonal method, progestogen-only pills, injectable, implant and intrauterine system) and the non-hormonal methods (copper intrauterine device, male and female sterilization) are more than 99% effective in preventing pregnancy. These methods, as well as emergency contraception, barrier methods and natural family planning methods, are described in this chapter. Evidence-based guidance on all methods of contraception and the use of contraception in specific groups or situations is available on the Faculty of Sexual and Reproductive Healthcare website (www.fsrh.org.uk).
Methods of contraception
Contraception can be considered as either hormonal (pills, patch, intravaginal ring, injectable, subdermal and the levonorgestrel-releasing intrauterine system, LNG-IUS) or non-hormonal (copper intrauterine device, Cu-IUD, barrier methods, sterilization, lactational amenorrhoea method and natural family planning). UK national statistics show that oral contraception remains the most popular method used by women of reproductive age with sterilization used by older women. Increasingly popular are the so-called long acting reversible contraceptive (LARC) methods, which include subdermal implants and both copper and levonorgestrel intrauterine methods. The National Institute for Clinical Excellence (NICE) guidelines on LARC indicate that these methods are very cost-effective in the prevention of pregnancy. With long duration of use (between 3 and 10 plus years of use depending on the method chosen and the age at insertion), low user failure rates, good satisfaction rates and high efficacy they are becoming increasingly popular in the UK.
Combined oestrogen–progestogen methods (pills, transdermal patch and intravaginal ring)
Combined hormonal contraceptives (CHC) work primarily by inhibiting ovulation via the hypothalamo–pituitary–ovarian axis to reduce luteinizing hormone and follicle stimulating hormone. In addition, cervical mucus is less favourable to sperm penetration and the endometrium is more atrophic. Most data on the use and safety of CHC relates specifically to the combined oral contraceptive pill (COC). This evidence is extrapolated to the transdermal patch and intravaginal ring, as they also contain oestrogen and progestogen.
Most currently available COC pills contain ethinyloestradiol (EE) and progestogens (synthetic progesterone), which include levonorgestrel and norethisterone (second generation), desogestrel and gestodene (third generation) and drospirenone (fourth generation). All oestrogen-containing COCs increase the risk of venous thromboembolism (VTE) above the background risk of 4–5 per 10 000 woman years among women not using a COC. This background rate is almost 10-fold higher than previously recognized, which means that the magnitude of additional risk of VTE associated with COCs is less than previously considered. In the past, studies have suggested differing VTE risk associated with different COCs, depending on the type of progestogen. However, in general, the risk of VTE in COC users appears to be double the risk of VTE in non-COC users. The risk is greatest in the first few months after initiating the COC and the risk falls to that of non-users within weeks of discontinuation. Nevertheless, the absolute risk for VTE is very small (Table 27.2). Risk factors for VTE must be considered when counselling women regarding COC use.
Table 27.2
Risk of venous thromboembolism associated with COC use
| Absolute risk of VTE per 10 000 woman-years | Circumstance |
| 4–5 | For women not using COC and not pregnant |
| 9–10 | For women using a COC |
| 29 | For women who are pregnant |
| 300–400 | For women who are immediately postpartum |
Women considering the COC should be informed of the potential risks and benefits associated with use (Table 27.3). Combined hormonal contraception is safe for most women, most of the time. Indeed, a non-smoker may safely continue with COC use to age 50 years if she has no contraindications for use. Deaths in COC users over 35 years of age are eight times more common in smokers than non-smokers. It is recommended that women who continue to smoke at the age of 35 years should use an alternative form of contraception (UKMEC category 3 if aged ≥ 35 years and smoking < 15 cigarettes/day or UKMEC category 4 if smoking ≥ 15 cigarettes/day). The use of COC may pose an unacceptable health risk in women with cardiovascular disease (myocardial infarction, stroke, hypertension, venous thromboembolism), liver disease (severe cirrhosis, active viral hepatitis, tumours) or migraine with aura at any age.
How to take the COC
Usually a fixed dose monophasic pill containing 20–35 μg of EE and a progestogen is used. There are no proven benefits of a biphasic or triphasic COC (where doses of the constituent hormones are varied) over a monophasic pill. A COC can be started up to and including day 5 of the menstrual cycle to provide immediate contraceptive protection. If started after this time, condoms or abstinence is advised for the next 7 days. Most COC packages contain 21 active tablets: one tablet is taken daily for 21 consecutive days, followed by a 7-day pill-free interval. A withdrawal bleed usually occurs in the pill-free interval due to the withdrawal of hormones which induces endometrial shedding. Women should be encouraged to take COCs daily at or around the same time every day. Missed pill advice is summarized in Figure 27.1. In general, one pill can be missed at any time in the packet without loss in efficacy or the need to use barrier contraception.
Drug interactions
Liver enzyme-inducing drugs (such as carbamazepine, some antiretrovirals, griseofulvin, rifampicin and the over the counter herbal medicine St John’s Wort) accelerate the hepatic breakdown of contraceptive steroids, thus potentially reducing the efficacy of the COC. The options for women using liver enzyme-inducing drugs long term who wish to continue with COC use is to increase the dose of EE to 50–60 μg/day (usually taking two pills per day), although use in this manner is unlicensed. In addition, it is recommended to reduce the pill-free interval. Condoms should also be used, however, as there are no studies to identify the correct dose of COC required to maintain contraceptive efficacy in these situations. The antibiotic rifampicin and the antifungal griseofulvin are potent liver enzyme inducers and advice is as for other liver enzyme-inducing drugs but in addition barrier contraception is advised for at least 4 weeks after cessation of these liver enzyme-inducing medications. An alternative is to use a method of contraception, which is unaffected by liver enzyme-inducing medication (such as a progestogen-only injectable, the LNG-IUS or a copper intrauterine device, Cu-IUD).
COCs can affect the levels of some drugs. Serum levels of the anticonvulsant lamotrigine are reduced with COC use. Lamotrigine levels can increase in the pill free week or when stopping COC.
Gut bacterial flora is involved in the breakdown of EE in the large bowel; this facilitates the secondary reabsorption of EE via the enterohepatic circulation. Antibiotics commonly alter this bowel flora and were considered to have the potential to reduce the secondary reabsorption of EE. However, new advice form the FSRH and the British National Formulary (BNF) is that women using combined hormonal methods who start a (non-liver enzyme inducing) antibiotic do not require additional contraceptive protection.
Follow-up
A 12-month supply of COC can be given at the first visit, but for some women a follow-up at 3 months may be appropriate to assess any problems and provide re-instruction if necessary. Blood pressure should be assessed annually, but women should be encouraged to attend at any time if problems arise. The pill should be discontinued if any potentially serious side-effects occur (e.g. chest pain, leg pain or swelling). Follow-up visits are also an opportunity to carry out other well-woman screening (e.g. blood pressure, cervical cytology).
The COC should be stopped and an alternative method used at least 6 weeks before any planned major surgery where immobilization is expected. If women are travelling to altitudes > 4500 m for more than 1 week, changing to an EE free method may be advised.
Combined hormonal contraceptive patch
The risks and benefits associated with transdermal patch (Evra®) use are as described as for the COC (Table 27.3). A patch can be applied to the abdomen, buttock or thigh on the same day each week for three consecutive weeks. This is followed by a patch-free week, during which time there is endometrial shedding and a withdrawal bleed. The transdermal patch should be changed every 7 days, although a single patch will provide effective contraceptive protection for up to 9 days. As for the COC, the transdermal patch can be started up to and including day 5 of the menstrual cycle to provide immediate contraceptive protection. If started after this time, condoms or abstinence is advised for the next 7 days.
Combined hormonal intravaginal contraceptive ring
The risks and benefits associated with intravaginal ring (Nuvaring®) use are as described for the COC (Table 27.3). The intravaginal ring is associated with serum concentrations of EE of only 15 μg. The ring is inserted into the vagina on the same day each month and is retained for 3 weeks. This is followed by a ring-free week, during which time the endometrium sheds and there is a withdrawal bleed. Once inserted above the pelvic floor it is not felt and it does not need to be removed during intercourse. As for the COC, the intravaginal ring can be inserted up to and including day 5 of the menstrual cycle to provide immediate contraceptive protection. If started after this time, condoms or abstinence is advised for the next 7 days.
Progestogen-only contraception
Progestogen-only contraception (pills, injectables, subdermal implant and the LNG-IUS) avoids the potential increased risks attributed to oestrogen. Most progestogen-only methods are associated with a disturbance in the bleeding pattern and this is often the main reason for discontinuation of these otherwise very effective methods. Other side-effects have been reported (abdominal bloating, weight changes, acne, headaches and mood changes) but few have been objectively related to progestogen use.
