A threesome being you, your mate,… and a baby.

St. John’s wort is one of those nice over-the-counter natural supplements millions of people take to remedy mild depression and anxiety.
I don’t have any personal experience to comment on how well it works, although I’d recommend against it for relationship-blues. You are more likely to feel worse if you – or the person you are seeing – is not ready to become a parent. If you are on St. John Wort, and you are taking birth control, and you combine the two with make-up sex… you may end up pregnant.

Why?

Because St. John’s Wort causes your body to metabolize the pill faster, i.e. you end up with too low a dose in your system to stay baby-proof.