The number of women becoming hospital consultants has jumped dramatically, narrowing the “gender promotion gap” with men, researchers have found.

The rise was due to an unusually large number of NHS vacancies created as older consultants decided to retire during the pandemic, according to the researchers, who compared the “considerable shift” to women taking on industrial jobs during the second world war.

Professor Carol Woodhams and colleagues from University of Surrey Business School and the University of Cyprus studied data on 10,485 NHS junior doctors from 2017 to 2023.

Junior doctors, or residents, spend at least six years doing training in specialist fields before they are eligible to apply for a job as a consultant.

The study, due to be presented to the British Academy of Management on Thursday, found that, from 2017 to 2023, 43% of British-trained male junior doctors at the end of their training were promoted to consultant, compared to just 25% of British-trained women. But the chances of promotion increased for men and women after March 2020, rising to 56% for British men and 48% for women.

This shift was “notable”, Woodhams told The Observer. “You don’t normally get that sort of considerable shift. It can happen, but it’s not typical. I’m starting to view it as similar to that reserve army of labour during both world wars – in times of crisis that reserve army moves up.”

The NHS, like many organisations, has been trying to encourage more women to enter the workforce. Such structural changes usually take a long time to take effect, Woodhams said, “but a crisis like Covid can produce unexpected and fairly grand effects”.

Woodhams was the lead researcher on the NHS’s Mend The Gap report in 2020, which highlighted gender pay gaps of 24% for hospital doctors and 33% for GPs, with women more likely to work part-time and men likely to hold more senior positions.

Women were much more likely to be affected by a parenthood penalty from taking time out of the workforce to look after children, which had an impact on their ability to progress, the report found.

“Women have to work harder, work longer and be better to demonstrate that they’re capable of promotion,” Woodhams said. “But the structures of medicine also indirectly discriminate against women. It takes a consultant 19 years to get to the top of their pay scale, after about 10 years of training. So if you’ve taken time out to look after children, you’ve lost four years or so. So the gender pay gap is the largest of any single occupation in the country.”

That may change, because the 19 different parts of the pay scale have now been reduced to five since the report, Woodhams said.

Having more women consultants may improve outcomes for female patients, according to Dr Isabel Stockton, a senior research economist at the Institute for Fiscal Studies (IFS).

“There is a lot of recent research in the US showing better outcomes of women being treated by women,” Stockton said. “So there are reasons to think that this matters, particularly in a profession like medicine, beyond the kind of general case that, of course, we would like everyone to have equal opportunities in all sorts of different professions.”

IFS research in April showed that some areas of medicine are much more likely to be male-dominated. In 2019, only 7% of trauma or orthopaedic consultants were women, compared with 77% of palliative care consultants.

Some types of medical specialisms may be “greedy work”, Stockton added, referring to Nobel laureate Claudia Goldin’s work about how some high-paying jobs required extremely long hours and could not be done by people with caring responsibilities.