If a woman has unscheduled intermenstrual bleeding while using a combined oral contraceptive (COC):

• Exclude or manage situations which could compromise the effectiveness of the COC:
• Missed pills: check how the COC is being taken and if any pills have been missed.
• Drug interaction: review if any new prescription or non-prescription medicines, or herbal/natural remedies, have been taken (e.g. antibiotics, St John's wort).
• Vomiting within 2 hours of pill taking: review the cause and duration of vomiting. Check pill taking (e.g. if a second dose of COC was taken).
• Severe diarrhoea: review the cause and duration of severe diarrhoea. Check pill taking (e.g. if additional pills have been taken to compensate for probable malabsorption).
• In all cases, check if additional contraception protection (e.g. condoms) was used.
• Exclude or manage other situations which could result in unscheduled bleeding, such as:
• Sexually transmitted infections.
• Risk of STI if the woman is under 25 years, or has a new sexual partner, or more than one partner in the last year.
• Pregnancy.
• Gynaecological conditions such as cervical cancer. Provided there is consistent and correct use of contraception, speculum examination is warranted:
• For persistent bleeding beyond the first 3 months of use.
• For new symptoms or a change in bleeding after at least 3 months of use.
• If the woman has not participated in a National Cervical Screening programme.
• If requested by the woman.
• After a failed trial of modification of COC treatment (at least 6–8 weeks).
• If there are other symptoms such as pain, dyspareunia, or post coital bleeding. (Note that these symptoms also warrant pelvic examination.)
• Consider the following treatment modifications:
• If the bleeding occurs early in the use of a new COC, encourage persevering for 3 months.
• If the bleeding is intolerable, consider stopping the COC for up to 7 days, and then restarting (and use alternative contraception while protection is lost).
• Changing the type of pill
• If taking 20 micrograms ethinylestradiol, increase to 30 micrograms ethinylestradiol.
• If taking 30 micrograms ethinylestradiol, increase to 35 micrograms ethinylestradiol.
• Increase the dose or changing the type of progestogen may help on an individual basis.
• Changing to another method of contraception.

• These recommendations are based on those issued by the Faculty of Sexual and Reproductive Healthcare (FSRH), formerly the Faculty of Family Planning and Reproductive Healthcare (FFPRHC), which advises clinicians to be aware of the likely causes of unscheduled bleeding in women taking the combined oral contraceptive (COC) [FFPRHC, 2007b; FSRH and RCOG, 2009] and the NHS Clinical Practice Guidance for the Assessment of young women aged 20–24 with abnormal vaginal bleeding [DH, 2010].
• Unscheduled bleeding and ethinylestradiol content:
• The FFPRHC guidance highlighted that unscheduled bleeding was more common in women using combined oral contraceptives (COCs) containing 20 micrograms of ethinylestradiol than in those using COCs containing more than 20 micrograms of ethinylestradiol [FFPRHC, 2007b].
• This was based on a Cochrane review which found that several COCs containing 20 micrograms of ethinylestradiol resulted in higher rates of early trial discontinuation (overall and due to adverse events, such as irregular bleeding), as well as increased risk of bleeding disturbances (both amenorrhoea/infrequent bleeding and irregular, prolonged, or frequent bleeding, breakthrough bleeding, and or spotting) than did the higher-oestrogen comparison pills [Gallo et al, 2005].