The study led by Gu Jiang, director of the School of Basic Medical Sciences affiliated to Peking University said that the finding does not mean that a global pandemic is near by.
"So far, no substantiated case of inter-human transmission has been observed. It largely depends on how the virus further mutates," the China Daily quoted him, as saying.
In the study, tissues taken from the body of a 24-year-old pregnant woman killed by bird flu were examined.
The analysis found that the virus had passed through the woman's placenta to infect the foetus.
Jiang said that besides woman's placenta, the virus was detected in the alimentary canal, brain, blood cells and respiratory tract. It was also found in the lungs and liver of the foetus.
He added that the findings had great significance in the treatment and prevention of the bird flu.
"For example, blood and faeces from people infected with the virus must be handled extremely carefully to avoid further spreading of the disease," he said.
Gregory Hartl, a spokesman for the World Health Organization, said that since mother and foetus function as two effective single bodies, passing of the virus was not really a case of human-to-human transmission.