Combined hormonal contraceptives

Estrogen-containing contraception raises venous clot risk on its own, and in someone who also carries factor V Leiden the two effects multiply rather than simply add, producing a substantially higher risk than either factor alone. US CDC Medical Eligibility Criteria place combined hormonal contraceptives in category 4 — an unacceptable health risk — for people with a known thrombogenic mutation such as factor V Leiden. The same guidance states that routine screening for these mutations before starting contraception is not recommended, and the wider thrombophilia-screening literature gives the reason: the variant is uncommon and screening everyone yields little benefit for its cost. This is background information about a documented gene-drug interaction. It is not a recommendation to start, stop or switch any contraceptive; that decision belongs with your clinician.

CDC US Medical Eligibility Criteria for Contraceptive Use — combined hormonal contraceptives, thrombogenic mutations (category 4). PharmGKB/ClinPGx carries a clinical annotation for the F5 variant with hormonal contraceptives (evidence level 2A); there is no CPIC prescribing guideline for F5. Background evidence: Mohllajee AP et al., systematic review of hormonal contraceptive use in women with thrombogenic mutations, Contraception 2006, PMID 16413847.