The statistical rate of abandonment was highest in Bangkok, at 7.43 per 100,000 babies, the deputy head of Mahidol University’s Institute for Population and Social Research told a seminar.

Assoc Professor Krittaya Acchawanichkul did not say how many babies were abandoned in maternity wards.

A study of nearly 2,500 pregnant women in the North and Northeast found that about 45 per cent of them had not planned their pregnancy and 16 per cent of them aborted the foetus for economic reasons, he told the seminar “Pregnancy, Abortion, Abandonment – Big Problems Left Ignored”.

Waranya Phithakthepsombat, of Planned Parenthood, said girls in their early teens are “most vulnerable to accidental pregnancy because they are in the early stage of puberty but have not been given enough education about sex and birth control”.

Both Krittaya and Waranya urged parents and the public not to treat young women who get pregnant accidentally harshly because this will cause mental distress and drive them to seek illegal abortions.

The chairman of the Medical Council, Dr Somsak Lohlekha, said doctors could perform abortions in cases where the woman suffers from an acute mental disorder or the foetus has severe genetic abnormality.

Previously, abortion was legal only in cases where the pregnancy was the result of rape or it threatened the life of the woman, Somsak said.