Nearly half of all teenage pregnancies in the wealthy Chinese city of Shanghai have been blamed on increased access to the internet.
China has strict controls over the internet
A doctor who runs a helpline for pregnant teenagers in the city reports that many of the girls said they had met the boys they had sex with online.
The news will disappoint China's ruling Communist Party, the BBC's James Reynolds in Beijing says.
The government has made policing the internet a priority.
It is concerned about people having access to internet sites that might be deemed harmful to the morals of the Communist state, our correspondent adds.
Dr Zhang Zhengrong has run her helpline in Shanghai for the last two years.
She said that 46% of more than 20,000 teenage girls who had called during that time said they had sex with boys they met on the internet.
Most of the boys did not stick around after learning about the pregnancy, she said.
And many of the girls did not understand sex and considered abortions to be harmless, she added. About 10% have had as many as three abortions.
"There were some who were unaware they were even pregnant until very late," she said.
Dr Zhang has appealed to parents and schools to pay more attention to sex education.