One of my many improving hobbies, along with throwing sticks in the park for former Big Brother participants, embroidering psalms and eating wine gums, is collecting the pronouncements of the medical and sociological professions about when I should bear children. If it were left to me, you see, I might not have them at all or, even worse, I might abide by my late grandmother's advice and only reproduce when I've got enough mince in the house for three.

This week, I added a sparkling gem to my already heavily jewelled collection when Dr Susan Bewley, consultant obstetrician at Guy's and St Thomas' hospital in London, claimed that "middle-aged" pregnancies are now as big a problem for the NHS as teenage ones, and that public policies must be set down to deal with them.

Over the past year, I have gathered enough data to know that prospective mothers (that means you, yes you) must not be too old (eggs become splintery balls of decayed DNA resulting in defective babies who will never earn their weight in tax revenue), too young (healthy eggs but feral children), too rich (you'll be tempted into unforgiveable moral compromises like paying for an nanny), too poor (you won't be able to afford a nanny), too fat (yuck!), too thin (you'll feed your baby skimmed breast-milk and sushi), too successful (your child will be like one of those monkey experiments, hugging your laptop for surrogate maternal warmth) or too unsuccessful (no one wants your welfare-state-leaching type to breed). In fact, before this latest news, I had just completed a complex set of calculations and determined that, if I can take an extra A-level, and maybe lose a stone, while getting pregnant a week next Thursday, and also pay off my credit card by the end of the first trimester, I can keep everyone happy and be left to rear my offspring in relative peace.

However, I had not factored in my potential cost to the NHS. I had assumed that if I waited to find a penis owner willing to service me and stick around for a few years afterwards, ensured I could afford a child, even though these days I gather they require a range of fripperies in addition to mince, and put this crushing responsibility off until I was of an age at which I probably wouldn't take the infant with me on all-night drinking binges and leave it in the gutter with my handbag, I had more or less discharged my duties to responsible society. I confess I also had a vague feeling that responsible society wouldn't begrudge me tapping the NHS for help if pregnancy did turn out to be a bit of a medical minefield.

I see now how selfish I was being. The NHS is starved of resources. This is stony, immutable fact, not a product of, or alterable by, political will or governmental re-prioritising, and so if it can't be solved by refusing to treat fat people or smokers, because people howl inexplicably at the unfairness, perhaps elderly prima gravidas can be shamed into doing their bit for the cash-strapped medical environment and popping those kids out by the Bewley-mandated age of 25. I, of course, am years late now, but I shall be writing to the Inland Revenue and asking them to tax me an extra 10% per annum until I am successfully impregnated. I hope that's OK with everyone.