Short answer: St. John's Wort induces the CYP3A4 liver enzyme that metabolises the estrogen and progestin in hormonal contraceptives — well-documented to reduce contraceptive effectiveness.
Why this interaction is stated with unusual directness
Linked to unintended pregnancies — a direct, serious consequence named explicitly rather than softened into a vague "may reduce effectiveness" caution.
What a specific, practical recommendation looks like
If you use hormonal birth control, either avoid Memocept or use a backup barrier method throughout your use — a direct, actionable instruction.
⚠️ Worth knowing: this applies to pills, patches, rings, and hormonal IUDs — all specifically named forms of hormonal contraception.