This is, in fact, rather a clever policy. The need for a confirmed hospital place puts a cap on the number of births, thereby easing the problem of medical congestion. Payment, and pre-payment, of course helps with the drain on the public purse.

It has been argued that mainland mothers are having the Hong Kong babies that SAR women seem reluctant to have, thus assisting with our developing demographic difficulties. Being entirely cynical about it, not only will Hong Kong get babies, but since actual physical residency here - given that the parents do not have right of abode - is difficult if not impossible, someone else will probably end up paying for their education and health care.

However, it leaves me feeling uneasy. On the miserly side, I would guess that even the higher fees rely on some implicit subsidies. Hong Kong people have no business subsidizing health care for those not part of our community; if we are going to be charitable, then the charity should be for the truly poor, not the relatively affluent Chinese who can afford the new fees.

It also appears that giving birth here allows mainland parents to avoid China's one-child policy. Even if this is now enforced largely in the breach, Hong Kong nevertheless becomes a party to evasion of Chinese regulations, whatever we might think of them, not the most comfortable position to be in.

But the larger issue is, as lawmaker Fernando Cheung Chiu-hung said recently in Legco, "mainland mothers giving birth in Hong Kong are not just a medical problem but also part of the population policy;" implicitly, anyway.

So, are we in favor of mainland mothers giving birth here and giving us new (potential) permanent residents, or not? If not, if we think that there is something illicit about mainland women traveling to Hong Kong to give birth and presumably secure residency for the child, then charging a fee rather legitimizes the exercise.

If we are, on the other hand, in favor of replenishing our stock of young, productive residents with the fruit of mainland loins, then one need ask if this is the best way to go about it.

The new policy in effect puts a price on Hong Kong residency. It is true that Hong Kong has put a price on residency before, but it was rather higher.

Furthermore, if, as has been reported, demand for "birth tours" has not slackened in spite of the fee increase, it will be interesting to see what prospective mothers end up paying for what is now a limited allocation of places.

If tour prices end up significantly in excess of actual hospital fees, or if there are "slotting fees," i.e. to get in line for a booking, then we will have handed a windfall to those who would in fact be trafficking in Hong Kong residency.

There is also no protection for less- than-affluent, but perhaps no less dedicated, mainland mothers who decide to go into debt to pay the fee now being levied.

And regardless of the ability of the parents themselves to reside in Hong Kong, the child presumably could if suitable guardians could be found or paid for, which given the potential benefits in social welfare, health care and schooling, might well be considered worth the cost. Or perhaps we will see new local boarding schools for children as young as five.

This has the potential to end up being rather sleazy, with possibly deleterious social consequences.

So while the policy change has much to recommend it, it has a certain ad hoc feel about it. Longer-term solutions might include a reinterpretation of the Basic Law as regards residency, changing social welfare regulations to reduce the potential attractiveness of residency for the child, or devising a population policy more sophisticated than merely placing quotas and levies on mainland births.

Even if one decides that the demographics are best solved by births rather than, for example, residency for mainland students upon graduation from a local university, should the sole criterion be position in the queue coupled with ability to pay? We are not selling flats here. All things being equal, one probably wants children whose parents have the means to educate them or who possibly have some cultural and linguistic affinity with Hong Kong.

But the main anomaly remains: having children with residency while their parents do not.