Basics of Contraception

There are many methods of contraception you need to be familiar with. It is a common task in OSCEs to counsel a patient about the different options. This involves discussing:

• Different options
• Suitability (including assessing contraindications and risks)
• Effectiveness
• Mechanism of action
• Instruction on use

It is worth noting that all forms of contraception are available free in the UK on the NHS.

Methods of Contraception

The key contraceptive methods available are:

• Natural family planning (“rhythm method”)
• Barrier methods (i.e. condoms)
• Combined contraceptive pills
• Progestogen-only pills
• Coils (i.e. copper coil or Mirena)
• Progestogen injection
• Progestogen implant
• Surgery (i.e. sterilisation or vasectomy)

Emergency contraception is also available after unprotected intercourse. However, emergency contraception should not be relied upon as a regular method of contraception.

UK Medical Eligibility Criteria

The Faculty of Sexual & Reproductive Healthcare (FSRH) has UK Medical Eligibility (UKMEC) guidelines published in 2016 (updated in 2019) to categorise the risks of starting different methods of contraception in different individuals.

There are four levels, from least risk of most risk:

• UKMEC 1: No restriction in use (minimal risk)
• UKMEC 2: Benefits generally outweigh the risks
• UKMEC 3: Risks generally outweigh the benefits
• UKMEC 4: Unacceptable risk (typically this means the method is contraindicated)

Explaining Effectiveness

The different methods of contraception are not equally effective. The effectiveness is expressed as a percentage. For example, the combined oral contraceptive is 99% effective. The only method that is 100% effective is complete abstinence.

What 99% effective means is that if an average person used this method of contraception correctly with a regular partner for a single year, they would only have a 1% chance of pregnancy.

It is essential to distinguish between the effectiveness of perfect use and typical use. This is especially important with methods such as natural family planning, barrier contraception and the pill, where the effectiveness is very user-dependent. Long-acting methods such as the implant, coil and surgery are the most effective with typical use, as they are not dependent on the user to take regular action.

The FSRH UKMEC guideline (2016) provides data on the effectiveness of each method with perfect and typical use. The table below is adapted from those guidelines to help your learning:

Specific Risk Factors

Exam questions frequently present an individual with specific risk factors and ask for the most suitable form of contraception for that person. It helps to remember key risk factors and their contraindications:

• Breast cancer: avoid any hormonal contraception and go for the copper coil or barrier methods
• Cervical or endometrial cancer: avoid the intrauterine system (i.e. Mirena coil)
• Wilson’s disease: avoid the copper coil

There are specific risk factors that should make you avoid the combined contraceptive pill (UKMEC 4):

• Uncontrolled hypertension (particularly ≥160 / ≥100)
• Migraine with aura
• History of VTE
• Aged over 35 smoking more than 15 cigarettes per day
• Major surgery with prolonged immobility
• Vascular disease or stroke
• Ischaemic heart disease, cardiomyopathy or atrial fibrillation
• Liver cirrhosis and liver tumours
• Systemic lupus erythematosus and antiphospholipid syndrome

Older Women

There are some additional considerations in older and perimenopausal women:

• After the last period, contraception is required for 2 years in women under 50 and 1 year in women over 50
• Hormone replacement therapy does not prevent pregnancy, and added contraception is required
• The combined contraceptive pill can be used up to age 50 years, and can treat perimenopausal symptoms
• The progestogen injection (i.e. Depo-Provera) should be stopped before 50 years due to the risk of osteoporosis

Women that are amenorrhoeic (no periods) when taking progestogen-only contraception should continue until either:

• FSH blood test results are above 30 IU/L on two tests taken six weeks apart (continue contraception for 1 more year)
• 55 years of age

Choice of Contraception Under 20

When prescribing contraception to women under 20 years:

• Combined and progestogen-only pills are unaffected by younger age
• The progestogen-only implant is a good choice of long-acting reversible contraception (UK MEC 1)
• The progestogen-only injection is UK MEC 2 due to concerns about reduced bone mineral density
• Coils are UKMEC 2, as they may have a higher rate of expulsion

Contraception after Childbirth

Fertility is not considered to return until 21 days after giving birth, and contraception is not required up to this point. The risk of pregnancy is very low before 21 days. After 21 days women are considered fertile, and will need contraception (including condoms for 7 days when starting the combined pill or 2 days for the progestogen-only pill).

Lactational amenorrhea is over 98% effective as contraception for up to 6 months after birth. Women must be fully breastfeeding and amenorrhoeic (no periods).

The progestogen-only pill and implant are considered safe in breastfeeding and can be started at any time after birth.

The combined contraceptive pill should be avoided in breastfeeding (UKMEC 4 before 6 weeks postpartum, UKMEC 2 after 6 weeks).

A copper coil or intrauterine system (e.g. Mirena) can be inserted either within 48 hours of birth or more than 4 weeks after birth (UKMEC 1), but not inserted between 48 hours and 4 weeks of birth (UKMEC 3).

TOM TIP: Remember that the combined pill should not be started before 6 weeks after childbirth in women that are breastfeeding. The progestogen-only pill or implant can be started any time after birth. 

Last updated August 2020