Newly-qualified women doctors outnumber their male counterparts by almost three to two, a survey suggests.
80% of women expect to take a career break, the survey suggests
The British Medical (BMA) found that 58% of doctors who graduated in 2006 were female compared with 51% in 1995.
The poll of 435 doctors suggests one in five female doctors anticipate working part-time for most of their career. The figure for men was one in 25.
The BMA will call for more flexible working hours at its annual conference in Torquay which starts on Monday.
It is calling for increased funding for flexible training schemes which allow junior doctors to work less than full time.
The government has already taken steps to cut the hours that doctors work.
Under the European Working Time Directive, junior doctors are no longer allowed to work over 58 hours.
This must be reduced to 48 by 2009. They are also entitled to take rests to break up on-call duties and night shifts.
Although the BMA welcomes these changes, it says they are not enough. It wants to see more flexibility in doctors' hours and training.
Dr Jo Hilborne, chairman of the BMA Junior Doctors Committee, said: "The medical workforce is changing rapidly and the NHS needs to wake up to the needs of its staff.
"It's not just the fact that more and more women are entering medicine - all staff should have the right to work-life balance."
According to the poll, almost half (48%) of women doctors say they want to train less than full-time at some point, compared to 15% of men.
Two-thirds of those questioned expected to take a career break at some point.
That figure broke down to 80% of women and 50% of men who anticipated a career break.
One junior medic, Dr Sarah Blayney, who is 24 and in her first year of work after graduating, said the current system left doctors with very little choice or flexibility.
Dr Blayney, who works at Arrowe Park Hospital, the Wirral, said: "The training jobs as they stand are all or nothing. You either do all the hours or don't get the post.
"I want to pursue a career in hospital medicine, which will mean me committing to a minimum of five years of fairly hefty on-calls.
"At the moment I am 24, single and am enjoying life. But in four or five years time my situation may have changed and I may not want to work those hours."
She said flexible working would be particularly relevant to female colleagues wanting to start a family, but said male colleagues were also interested in changing their hours. For example, some wanted to take time out to travel, she added.
"It should not need to compromise training. Doctors appreciate that they need to put the time in. It's about having more flexibility."
The study, which began in May 2006, also found trainee doctors are now more likely to enter the medical profession at a later stage of life - the average age of respondents was 27, compared to 24 in 1995.
One of the doctors was 47 when they graduated.
And 15% of the doctors had already worked in a different profession before entering medical school.
Most were in debt when they graduated. The average amount owed was £20,798 with the highest level of debt standing at £80,000.