New European rules come into force on Friday which mean some women are set for a shock when their next car insurance quote lands on the doormat.
The new gender-neutral rules stem from a European Court of Justice ruling last year which means insurers are no longer able to consider a customer's gender when calculating how much they pay for their car or life insurance, or what their retirement income should be.
Women have benefited from smaller car insurance premiums due to their lower accident rates, and predictions as to how they will be affected have varied widely.
Some analysts believe younger women could see their premiums almost double, while others forecast that the increases could be more gentle than expected, provided insurers can piece together enough information about someone as a driver.
Young women are likely to bear the brunt of the increases, due to the higher accident rates of young men, which experts warn could force many younger female drivers off the road. Meanwhile, some men could see a small reduction in their premiums.
While the full impact of the changes is yet to be seen, price comparison website Gocompare has already seen women's premiums jump in recent days. At the start of November the typical cheapest quote offered to a woman was £748 but by the end of last week this crept up £114, or 15%, to £862. The site, which says it has monitored more than 10 million car insurance quotes since January last year, said this is the biggest shift it has seen in premiums so far.
Another comparison website, MoneySupermarket, said that although it is yet to see any great spike in prices, this could change quickly as insurers jostle for position in the fast-moving market. The website's insurance expert, Kevin Pratt, said: "There may be a period of a few days or weeks when the market adjusts. There are over 100 companies trying to get business and they will inevitably monitor what the others are doing."
Mr Pratt said he hopes insurers will place greater emphasis on other factors to make sure drivers can still get a reasonable price, such as their job, type of car, driving record, any security measures on the car and age. There is no reason why someone cannot continue to be deserving of the premium they are paying at the moment, provided the insurer can find out sufficient information about them, he said.
Michael Ossei, a personal finance expert at uSwitch.com, predicted that women aged between 17 and 25 could see premiums "almost double". The website said that more than a third of the women it has surveyed would have to cut back their living expenses to cope with higher premiums and one in 10 (11%) may end up selling their car. There are also signs that it is getting harder for young people to get a broader choice of car insurance quotes.
The Association of British Insurers has placed guidance about the changes on its website. It urges customers not to focus on price alone but to shop around for the most suitable deal. Drivers can push their costs down by paying their car insurance in one lump sum rather than instalments, having a "black box" installed in their car which rewards careful driving with lower premiums and having extra security measures fitted, it suggests.