Usually I am very loathe to support government limitations on the medical services patients may seek. However, medical procedures designed to create new life directly affect people other than the patient, ie the children who are created. This alone justifies government intervention. The power to add more people to society also implies reactionary or limiting powers by the society over the creators in the context of maximising social welfare eg population engineering in Asia.
In reference to this article, for a morbidly obese mother to take radical medical action to become pregnant is unethical and abusive towards the child. For the NHS to be expected to finance such services is absolutely detrimental to British society. The demand of well-educated, hard-working labour to immigrate to Great Britain more than compensates for an otherwise negative population growth rate. Therefore, there is no reason for the government to finance such dangerous and expensive measures to add more children to the population.