Women from ethnic minorities are more likely to smoke or drink during pregnancy the longer they have lived in Britain

Immigration also causes health problems:

The British Medical Journal study also showed they were more likely to stop breastfeeding sooner.

The Institute of Child Health team said doctors should not assume ethnic minority women did not smoke or drink.

A maternal health expert said it was "sad" that unhealthy habits became normal among immigrant groups.

The research looked at women taking part in the Millennium Cohort Study who had babies between September 2000 and January 2002.

In 2001-02, 7.6% of the population was from an ethnic minority group - up 44% during the previous decade.

Women from ethnic minority groups are known to be less likely to smoke or consume alcohol than the general population, but the researchers looked at how living in a Westernised society affected their habits.

The researchers studied 6,478 mothers of white British or Irish origin and 2,110 mothers from ethnic minority groups who had either migrated to the UK themselves, or were first or second generation immigrants.

Around a third of British and Irish mothers smoke or drank alcohol during pregnancy, compared with a sixth of all the ethnic minority mothers.

And just 27% of British or Irish mothers breastfed for at least four months, compared with 40% of those from ethnic minorities.

But, among women from ethnic minorities, first and second generation mothers-to-be were more likely to smoke and drink during pregnancy than immigrants.

Professor Catherine Law, of the Institute of Child Health, said: "Health professionals should not underestimate the likelihood of women engaging in risky health behaviours because of their ethnicity."

She said smoking and alcohol consumption rates did vary between ethnic minorities, but that in all the groups studied, the rates were increasing.

BBC News.