The number of average sized women with bigger bust lines is increasing, a new survey has found.
The number is said to have gone up considerable, with the most common bra cup size increasing from a B to a DD in the past 50 years.
Women's health experts blame a range of environmental and hormonal factors, while lingerie specialists say some women have realised they have been wearing the wrong bra size for years.
According to bra fitter Esther Labi, there has been a sharp increase in slim women, particularly teenagers, with very large chests up to a F or G cup.
"A lot of teenagers wear a 10F - they're slim girls but they have boobs," the Sydney Morning Herald quoted her as saying.
Labi's company, Storm in a D Cup, caters for well-endowed women who often have had an unsatisfying experience in a mainstream store.
"There is a frustration in clothes not being available when you're small in the body but big in the bust," she said.
Myer lingerie fitter, Carol Ferlito, says about half of all the customers she sees are bigger than a DD cup. According to official company data, plus-size bras account for one-third of total sales.
Ferlito regularly fits girls aged 11 and 12 in sizes D and DD, even for their first bra.
"The younger generation are developing a lot earlier. Sometimes mums don't realise how big their daughters are," she said.
Susan Davis, a professor in women's health at Monash University said, bigger bust lines are typical in societies that have become more westernised, including in Asia.
The combination of early-onset puberty, delaying childbirth and an increase in overall body fat create a hormonal cocktail that is conducive to bigger breasts.
"If you go through puberty at age 12 you have a longer time for your breasts to get bigger. Fat tissue produces oestrogen which leads to increase in breast tissue," she stated.
Professor Davis believes oestrogens in the food chain and exposure to chemicals, rather than synthetic hormones found in the pill and hormonal replacement therapies, are also causing women's chests to expand.