Many pregnant women who have had their full quota of children also have abortions to prevent unwanted births.

The newspaper cited a survey done by a Shanghai-based army hospital which found that more than 70 percent of women who called to the hospital hotline number didn't know how sexual transmission causes HIV/AIDS.

Only 30 percent of callers knew how to avoid pregnancy, and only 17 percent were aware of venereal diseases.

Researchers say that the inadequate knowledge about sexual health leads to high number of abortions and other birth-related complications.

'Sex education needs to be strengthened, with universities and our society giving more guidance,' Li Ying, a professor at Peking University, told the newspaper.

'Chinese parents are reluctant to teach their children about sex, so more needs to be done on sex education,' Li added.