The combined oral contraceptive pill (COC) is one of the most popular methods of contraception currently used in the UK

Mechanism of action

  • main: stops ovulation
  • also: thickens cervical mucus (reducing chance of semen entering uterus) and thins endometrial lining (reducing chance of implantation)

Adverse effects

  • increased risk of venous thromboembolic disease
  • increased risk of breast and cervical cancer
  • increased risk of stroke and ischaemic heart disease (especially in smokers)
  • temporary side-effects such as headache, nausea, breast tenderness may be seen


The decision of whether to start a women on the combined oral contraceptive pill is now guided by the UK Medical Eligibility Criteria (UKMEC). This scale categorises the potential cautions and contraindications according to a four point scale, as detailed below:
  • UKMEC 1: a condition for which there is no restriction for the use of the contraceptive method
  • UKMEC 2: advantages generally outweigh the disadvantages
  • UKMEC 3: disadvantages generally outweigh the advantages
  • UKMEC 4: represents an unacceptable health risk

Examples of UKMEC 3 conditions include
  • more than 35 years old and smoking less than 15 cigarettes/day
  • BMI > 35 kg/m^2*
  • family history of thromboembolic disease in first degree relatives < 45 years
  • controlled hypertension
  • immobility e.g. wheel chair use
  • carrier of known gene mutations associated with breast cancer (e.g. BRCA1/BRCA2)

Examples of UKMEC 4 conditions include
  • more than 35 years old and smoking more than 15 cigarettes/day
  • migraine with aura
  • history of thromboembolic disease or thrombogenic mutation
  • history of stroke or ischaemic heart disease
  • breast feeding < 6 weeks post-partum
  • uncontrolled hypertension
  • current breast cancer
  • major surgery with prolonged immobilisation

Diabetes mellitus diagnosed > 20 years ago is classified as UKMEC 3 or 4 depending on severity

Changes in 2016
  • breast feeding 6 weeks - 6 months postpartum was changed from UKMEC 3 → 2