In recent years, approximately 4.4 million women in the U.S. have been diagnosed with bipolar disorder and women of childbearing age having the highest number of diagnoses. 

A new study has found that physiological changes during pregnancy reduce the effects of lamotrigine, a drug commonly prescribed for people diagnosed with bipolar disorder, making women more vulnerable to recurring episodes. The new findings will help psychiatrists and physicians prevent bipolar manic and depressive symptoms during pregnancy, which are risky for the health of the mother and her unborn child.

There also is little information and research to guide dosing for psychiatric medications during pregnancy so physicians may not realize medication needs adjusting to prevent symptoms.

The new paper shows the blood concentration of lamotrigine decreases in pregnant women. About half of the women in the study had worsening depressive symptoms as their lamotrigine blood levels dropped. The drug levels fall because women have increased metabolism during pregnancy.  

"Now physicians change the dose of the drug in response to women's symptoms worsening," said lead investigator Crystal Clark, M.D., an assistant professor of psychiatry and behavioral sciences at Northwestern University Feinberg School of Medicine and a psychiatrist at Northwestern Memorial Hospital. "We need to optimize their medication dosing so they stay well."

The study results will help physicians understand how to increase their patients' doses during pregnancy and then reduce them postpartum to avoid toxicity, Clark said. Guidelines for prescribing the drug for pregnant women with the disorder also are included.

Depressive episodes -- as opposed to manic -- are most likely to recur in pregnant women with bipolar disorder.

"The safety of the fetus is at risk," Clark said. "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."