Breakthrough Bleeding with Combined Hormonal Contraception

Most women find that combined hormonal contraception (CHC) provides reliable cycle control. Indeed the combined oral contraceptive pill (COCP) is often prescribed for the management of menstrual disorders such as menorrhagia and dysfunctional uterine bleeding.¹ However, although new formulations with low doses of oestrogen offer health benefits they may provide less satisfactory cycle control.² The risk of bleeding may also be related to the dose and type of progestogen. Unfortunately, methodological differences between studies have also made it difficult to compare rates of breakthrough bleeding between different preparations.¹

Irregular bleeding whilst taking CHC is a common problem³ with up to 30% of women experiencing breakthrough bleeding or spotting during the first cycle of treatment.⁴ Such bleeding occurs unpredictably⁵ and may cause significant disruption and anxiety for users.⁶ Irregular bleeding is thus one of the most common reasons for discontinuation of CHC.⁷

Normal endometrial maturation depends on complex interactions between oestrogen and progesterone. CHC provides a continuous supply of oestrogen and progestogen to the endometrium. The low dose of oestrogen in modern CHCs is insufficient to maintain endometrial integrity⁴ and the opposing effect of progestogen promotes atrophy of glands and stroma. The resulting endometrium is thin, fragile and prone to bleeding.¹

No relationship has been identified between serum steroid levels and bleeding.⁸ In the absence of missed or late pills, vomiting or drug interactions, reduced contraceptive efficacy has not been proven.³

Patient factors¹

• Poor compliance with medication is the most likely cause of irregular bleeding.
• Cigarette smoking has anti-oestrogenic properties and may affect cycle control.

CHC formulation factors

• COCPs containing only 20 mcg of ethinyloestradiol cause more disrupted bleeding patterns than those containing higher doses.⁹
• Monophasic and biphasic formulations provide similar cycle control.¹⁰
• Triphasic formulations may offer better cycle control.¹¹
• First generation progestogens e.g. norethisterone, provide poorer cycle control than second (levonorgestrel) and third generation progestogens.¹²
• Of third generation progestogens, gestodene may afford better cycle control than desogestrel.¹¹
• CHC patches are associated with more irregular bleeding than COCPs during initial treatment, but rates are similar after three months of use.¹³

Recommendations to prevent bleeding

• Use COCPs containing 30 mcg of ethinyloestradiol combined with a second generation progestogen as first-choice.
• There is no evidence that starting CHC mid-cycle reduces the incidence of bleeding.¹¹

Other considerations

Although CHC is a common cause of irregular bleeding, other unrelated causes must also be considered such as:⁴

• Chlamydia or other sexually transmitted infections
• Intrauterine or ectopic pregnancy³
• Endometrial or cervical polyp⁴
• Cervical cancer³
• Endocrine abnormalities such as hypothyroidism, hyperthyroidism, hyperprolactinaemia
• Bleeding disorders⁴