Newborn babies are being traded on a lucrative black market in Indonesia that could involve hundreds of children a year, some going illegally to parents offshore.

Pregnant women have been propositioned to give up their babies at pre-natal health checks and new mothers approached in the maternity ward, according to a court case due to start on Tuesday that exposes the trade.

Pregnant women are propositioned to give up their babies at pre-natal health checks and new mothers are approached in the maternity ward. Credit:Getty

The country's child protection commission says thousands of children have been bought and sold over the past 15 years.

In 2004 the illegal adoption issue caught out an Australian couple, who believed they were getting a baby legally but were rejected by the Australian authorities when they tried to have their child's citizenship changed. The couple exposed the agent behind that scam, lawyer Isnania Singgih, who spent four years in jail.