One of Australia's hottest-selling products, infant formula, has been caught up in the market woes about the health of China's economy.

Shares in some of Australia's most-popular infant formula brands have plummeted in the past month amid increasing concerns from analysts that the world's second-largest economy will cool further this year.

Phin Ziebell said demand for infant formula in China should continue to remain strong.

On Tuesday, Beijing said fourth-quarter growth was less than expected while China's economy expanded 6.9 per cent in 2015, the slowest pace in 25 years.

Trans-Tasman producer, a2 Milk, has fallen 26.7 per cent to $1.58 in the past four weeks, while Bellamy's Organic has eased 14.6 per cent to $13.22. This compares with the S&P ASX 200 Index shedding 8.3 per cent in the same period.