Research has uncovered an important relationship between pregnancy and a drug for bipolar disorder, which could be increasing risks to mothers and unborn children.

A study from Northwestern University in Chicago has found that the blood concentration of the commonly used drug ‘lamotrigine’ decreases in pregnant women, leaving some more vulnerable to worsened bipolar manic and depressive symptoms during their pregnancy.

Lamotrigine is available in Australia on the Pharmaceutical Benefits Scheme, it is often known by a brand name ‘Lamictal’.

Researchers have suggested the level of lamotrigine falls more rapidly due to the increased metabolism during pregnancy in a study published by the American Journal of Psychiatry.

The finding comes from one of the first in-depth studies of how physiological changes during pregnancy can reduce the effects psychiatric medication. The new findings will help authorities prevent bipolar manic and depressive symptoms during pregnancy, which are risky for the health of the mother and her unborn child.

“The safety of the foetus is at risk,” said lead investigator Dr Crystal Clark, an assistant professor of psychiatry and behavioural sciences at Northwestern University and a practicing psychiatrist.

“Pregnant women that are depressed are less likely to take care of themselves which often leads to poor nutrition, lack of compliance with prenatal care and isolation from family and friends. It has also been linked to premature births and babies with low birth weights among other poor birth outcomes.”

“Now physicians change the dose of the drug in response to women's symptoms worsening,” Dr Clark said

Details in the new paper are intended to help physicians understand how they might increase their patients’ doses during pregnancy, and then reduce them post-partum to avoid toxicity.

More information is available from the American Jounal of Psychiatry.