By Jill McGivering
More research is needed on the cause of birth defects
The birth defect rate rose again in the Chinese capital Beijing last year, mirroring increases elsewhere in the country, according to figures.
The city's birth defect rate has almost doubled in the last decade.
The causes of such defects are not clear, but there are concerns they could be related to heavy pollution.
A growing number of babies in China are being born with abnormalities - ranging from extra fingers and toes and cleft lips to congenital heart disease.
In Beijing last year, according to Chinese officials, the rate was 170 per 10,000 births. That is significantly higher than the global average.
This fits with other reports about sharp rises in birth defects across the country, in both rural and urban areas.
Some provinces with large coal and chemical industries seem to have some of the highest rates.
It is hard to know for sure what's causing these defects, but they are helping to fuel broader concern about the health impact of acute air, water and soil pollution in China.
An editorial in Tuesday's China Daily newspaper broadened the argument by pointing to modern urban lifestyles as another possible factor for the growth in birth defects.
As well as worrying about pollution, it said, individuals should also think twice about their busy, stressful schedules.
All this is politically sensitive for China.
More research is needed, for example, detailed mapping to see what correlation there is between different types of defect and pollution levels.
Improvements in health facilities, which give better monitoring of newborns and better diagnosis, may also account for part of the increase.