We all know as a matter of indisputable fact not to be questioned by anyone - on pain of death - that our offspring will never, ever have sex.
We know this (the happily delusional tribe of mums and dads of young girls who begin to view the lovely neighbourhoodboys as the lone males on the fringe of the pack in some suburban Richard Attenborough moment) like we know the sun will come up and that we were supposed to buy power company shares - because we are, after all just ordinary Kiwi mums and dads.
So when the small person comes home and insists that she needs to have her HPV vaccine that will protect her against a host of cancers as well as genital warts and cervical cancer, which she maturely outlines in a Powerpoint presentation, I nod and smile encouragingly on the outside.
On the inside, I have already gone into the foetal position and am rocking and shaking my head whilst screaming ... Nooooooooooooo! They're all growing up too fast!!! "Perhaps we should wait a few years?" I ask hopefully. "Mmm. I thought you might say that. I've googled 'cervical cancer', it really doesn't sound like fun. Just be sensible and sign the paper.'
I remind myself that in order to maintain my tentative hold on being the adult in the room I should perhaps start acting like one. I stare into space and briefly contemplate joining a Christian fundamentalist sect where this won't be a problem.
I could arrange a marriage for her with the boy of my choice (provided it was a matriarchal cult - unlikely but I hold that thought) and this choice would not have to be made at all. Gloriavale would be nice this time of year ... I could get used to a bonnet.
"Mum! Just sign the paper and stop being silly!"
Now if there were a revolution, the first people I would shoot would be the selfish people who cruise on the coat-tails of the herd and refuse to vaccinate their children.
Given that I'm the world's biggest fan of hospital births and vaccinations for the simple reason that they both stop people dying - I'm struggling with my reticence to sign the parental permission.
I go to sign the paper and stop. "Why is this just for girls? How come the boys aren't getting it? Isn't that sexist?"
"Mum - the boys can get cancer - that's their choice but this is free, it stops a whole heap of bad stuff so I'm having it - you just sign the papers."
I suspect that the decision for boys not to have the vaccination is less the boys' doing and more about public policy and purse.
If we're going for herd immunity though - someone needs to think about the other 50 per cent.