New York, May 24 (IANS): Mothers who smoke during pregnancy can increase the risks of mental disorders in their babies, warns a study.

The results showed that a higher maternal nicotine level in the mother's blood was associated with a 38 percent increased odds of schizophrenia among their offspring.

Nicotine readily crosses the placenta into the foetal bloodstream, specifically targets foetal brain development, causing short- and long-term changes in cognition and potentially contributes to other neuro-developmental abnormalities.

"To our knowledge, this is the first biomarker-based study to show a relationship between foetal nicotine exposure and schizophrenia," said senior author Alan Brown from Columbia University's medical centre in the US.

"We employed a nationwide sample with the highest number of schizophrenia cases to date in a study of this type," Brown added in the paper published online in the American Journal of Psychiatry.

The team examined nearly 1,000 cases of schizophrenia and matched controls among offspring born in Finland from 1983-1998, who were ascertained from the country's national registry.

The findings persisted after adjusting for important confounding factors including maternal and parental psychiatric history, socio-economic status and maternal age.

Heavy smoking based on cotinine, a reliable marker of nicotine in maternal sera, was reported by 20 percent of the mothers of cases, but only 14.7 percent of the mothers of controls.

Smoking during pregnancy is known to contribute to significant problems in utero and following birth, including low birth weight and attentional difficulties.

"These findings underscore the value of ongoing public health education on the potentially debilitating and largely preventable, consequences that smoking may have on children over time," Brown noted.

The researchers also found that offspring of mothers who reported smoking during pregnancy have an increased risk of bipolar disorder.