You could begin a low-key and very short discussion around the subject.
Provided you have time to work this through, you can expand on the subject on a regular basis until you eventually feel the groundwork is sufficient to directly broach the subject in question.
Do bear in mind your parents are probably not dumb, and will maybe have an idea where you're heading, even if they don't say so.
If you don't have time to approach the subject gradually, you'll simply have to ask them, in the nicest possible way, and be prepared for their reaction. They might surprise you.
If they take it badly, be prepared for that, too, and don't react in a hostile manner.
Something that seems of huge importance today will inevitably fade into unimportance with time, unless emotions get out of control.
Friends of mine, when their daughter reached puberty, bought a sex-education book, all sealed in plastic. It sat there on the bookshelf, waiting for the day they had the courage to open it and face the questions. They never found the courage. It stayed sealed. Now the girl is married and has children, and all her parents' agony over her sex education was pointless. But she learned from this that sex was a huge and horrific subject, never to be spoken of. I wonder how much good that did her?
If your parents have similar feelings on a range of difficult subjects, you'll just need to be more mature than they are.