Junior doctor leaders are due to meet next Saturday (7th) to decide their next actions after this week's two-days of full labour withdrawal.
Although the strike gained the backing of 78% of junior doctors rostered to work during the period and led to the cancellation of tens of thousands of operations and appointments, there has been little sign of the government backing down over contract imposition.
The British Medical Association junior doctors' committee is known to be considering an indefinite strike as one option.
Yesterday NHS England chief executive Simon Stevens wrote to trust chief executives and to clinical commissioning groups ordering them to "refresh" their contingency plans to prepare for extended action.
Hospitals are also expected to set out their response to an indefinite withdrawal of emergency and elective care.
The letter was also signed by Jim Mackey, chief executive of NHS Improvement.
It states: "Unfortunately it also appears that further industrial action is possible, including the possibility floated by the BMA of a full and indefinite withdrawal of junior labour.
"This will clearly have wide-ranging impacts on patients."
The letter cites the Civil Contingencies Act, suggesting the NHS might draw on military doctors in the event of extended strike action.
Junior doctors' committee chair Dr Johann Malawana, who obtained the letter, tweeted: "Would obviously be better if the signatories spoke to the Secretary of State and convince to lift imposition."
In the year from 2014 to 2015, some 76% of the 6,030 patients undergoing the procedure were female, according to the Health and Social Care Information Centre.
The figures highlight the growth of obesity in England. They show that 26% of the population were obese in 2014 compared with 15% in 1993.
And by 2014 some 3% of the population was defined as morbidly obese - including 4% of women and 2% of men.
Among children more than 20% were obese or overweight at the time of starting primary schools while about a third were overweight or obese by the age of 11.
But in primary care prescriptions for obesity reduced, the figures show. Some 519,000 prescriptions were issued in 2014 compared with 563,000 in 2013.
Izzi Seccombe, health spokeswoman for the Local Government Association, said the figures were "extremely worrying."
She said: "The problem will only get worse unless we take urgent action, with the number of obese adults in the country forecast to soar by a staggering 73 per cent to 26 million people over the next 20 years
“The fact that the number of obesity-related hospital admissions for children has more than doubled since 2004/5 underlines why it is vital that the Government uses its forthcoming childhood obesity strategy to address what is now one of the major health dangers of the 21st century."
And in nine countries, including Canada, the virus has been transmitted between people, according to the World Health Organisation.
WHO said six countries have now reported cases of microcephaly and other foetal malformations linked to congenital infection.
In total some 52 counties now have mosquito-borne transmission of the virus.
The World Federation of Neurology said yesterday it had established a working group on the virus, warning of potentially widespread neurological complications from infection.
President Professor Raad Shakir, from London, UK, said: “The Zika virus is more and more showing its ugly face, and the international community increasingly realises the dimensions of this problem.
"Neurological expertise is crucial to deal with the consequences of what proves to be a devastating epidemic."
He added: “In many areas particularly hit by Zika virus there is a clear lack of neurological resources, a shortage of neurologists, in particular also child neurologists, a lack of neurophysiological testing possibilities, and scarce intensive care facilities.
“If we do not overcome these problems there shall be more unnecessary deaths which would not have happened if the affected individuals would have lived in less deprived parts of the world.”
The working group chair Professor John England, from the Louisiana State University, New Orleans, USA, said: “Of great concern is the fact that the geographical distribution of the virus has steadily and rapidly expanded. There is great concern that the virus outbreak will continue to spread to other countries and territories.
"It has already reached the Caribbean countries and may spread to the southern United States and other countries where the virus mosquito vector (Aedes aegypti) thrives."
In both countries about nine out of ten doctors agreed that shortage of resources was putting patients at risk.
Both surveys were commissioned by the Royal College of GPs through pollsters ComRes in advance of national elections in the two countries.
In Scotland some 77% of GPs worried about missing something serious - while in Wales this proportion was 84%.
The surveys found that 9% of GPs in Scotland plan to quit within 12 months. Some 58% hoped to leave or reduce hours in the next five years while in Wales this proportion was 56%.
Dr Miles Mack, college chair in Scotland, said: "A wholesale departure of GPs now looks likely given the current conditions the profession faces. In that instance, patient safety clearly will suffer further.
“General practice in Scotland is a defining issue in this Scottish Parliamentary election.
“RCGP Scotland has been warning of this snowballing state of affairs for two and a half years now and has put forward positive solutions to see the crisis resolved."
The Welsh college chair Dr Rebecca Payne said: "Wales desperately needs more GPs to help alleviate the pressure and ahead of the Assembly election, we as a College in Wales are calling for 400 more GPs by 2020, as well as a rapid expansion in other professionals trained to work in primary care such as nurses, pharmacists and paramedics.
“The next Welsh Government must act on this and copy the massive English investment announced last week into general practice to support an increase in the general practice workforce and a transformation in how services are delivered."
ComRes questioned 100 doctors in Wales and 150 in Scotland.