Women with bipolar disorder at 50 percent greater risk of delivering preterm babies

Women who have been previously hospitalized for bipolar disorder are nearly twice as likely to have premature babies compared to women without a history of mental illness, according to a new study by researchers at Women's College Hospital and the Institute for Clinical Evaluative Sciences (ICES).

The study, published today in the American Journal of Obstetrics and Gynecology, shows pregnant women with bipolar disorder are at greater risk of having premature babies and other serious complications. While the study did not examine the causes that led to these findings, the researchers suggest that women may be able to reduce risk to their babies by modifying lifestyle and behavioural factors.

"Bipolar disorder is the sixth leading cause of disability among women of reproductive age and yet research tells us very little about how to ensure the best possible outcomes for mothers and babies," said Dr. Simone Vigod, lead author of the study, psychiatrist at Women's College Hospital and scientist at ICES. "Knowing the potential impact it may have, as well asany modifiable risk factors, will help us as doctors provide the best treatment possible for our patients."

In the study, the researchers examined the health records of women who delivered a single baby from 2003 to 2011. The researchers compared women previously hospitalized for bipolar disorder and major depressive disorder, to the general population. They found:

Women with bipolar disorder were twice as likely to have preterm birth compared to women without a history of mental illness.

Babies born to women with bipolar disorder were more likely to be large for their gestational age, in contrast to babies born to women with depression who were more likely to be born small for their gestational age.

Babies born to women with bipolar disorder were more likely to have higher rates of congenital malformations and other complications.

Babies born to women with bipolar disorder were more likely to be readmitted to hospital within 28 days of discharge.

"Outcomes like preterm birth are concerning, because they are known to negatively impact health in childhood and later adulthood," added Dr. Vigod. "While we don't know the exact cause of preterm birth and other negative outcomes, we do know mental health symptoms can promote the secretion of stress hormones that can lead to preterm birth."

What's more, psychiatric medications, genetics, health and lifestyle behaviours - including low socioeconomic status, a lack of exercise and obesity, poor nutrition and smoking - may also play a role, she noted.

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"Perinatal outcomes among women with bipolar disorder: A population-based cohort study," was published today in the American Journal of Obstetrics and Gynecology.