BEIJING -- The percentage of women dying in childbirth has reduced rapidly across China in the past two decades, according to a recent study.

The study, a systematic assessment of maternal mortality ratios down to the county level, was conducted by researchers from West China Second University Hospital affiliated with Sichuan University.

Researchers collected data from China's national Annual Report System on Maternal and Child Health and used data mining to analyze the maternal mortality ratios for 2,852 counties in China between 1996 and 2015.

Results showed that in the past two decades, almost all counties in China had achieved the annual decline rate of 5.5 percent, a target set in the Millennium Development Goal.

China has seen fast declines in maternal mortality ratios from 108.7 per 100,000 live births in 1996 to 21.8 per 100,000 in 2015, with an annual decline of 8.5 percent.

Researchers also analyzed inequality of maternal mortality ratios at the country and provincial levels. They found that counties with lower maternal mortality rates were mainly concentrated in eastern and southeastern China.

The study said China needed to further improve the accessibility and quality of maternal health care in rural areas by nurturing more well-trained midwives.

This study will be helpful for other developing countries that are trying to achieve the Sustainable Development Goal on improving maternal health.

The study was published in the journal Lancet.