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Study finds pregnant women with bipolar disorder at increased risk for preterm birth

Nov. 7, 2014

New research indicates that pregnant women with bipolar disorder may have an increased risk of delivering a preterm baby, compared to women with no history of mental illness.

Researchers at Women’s College Hospital (WCH) and the Institute for Clinical Evaluative Sciences (ICES) found that women who had previously been hospitalized with bipolar disorder had almost double the risk of delivering a preterm baby as women with no mental health diagnoses. The study also found that babies born to women with bipolar disorder were more likely to be very large, and more likely to have certain newborn health problems and congenital malformations.

The study also found that risk for premature birth and neonatal health problems was also increased in babies born to women who had been hospitalized with major depression.

The study used data on 437,941 women who gave birth in Ontario. All of the women became pregnant between April 2002 and March 2010. There were 1,859 women who had been hospitalized for bipolar disorder within five years of becoming pregnant. Another 3,724 women had been hospitalized for major depressive disorder within five years of becoming pregnant. The remaining 432,358 women had no documented mental health problems.

The researchers led by Dr. Simone Vigod, a psychiatrist at WCH and a scientist at both Women’s College Research Institute and ICES, compared pregnancy and newborn health outcomes of the women who had been hospitalized for mental illness to those of the women with no mental health diagnoses.

They found that the women who had been hospitalized for bipolar disorder had a 95 per cent higher risk of premature delivery than the women with no mental illness. More than one in 10 of the women with bipolar disorder delivered preterm. Women with bipolar disorder were also 29 per cent more likely to have an infant that was very large for its gestational age.

Earlier studies had linked major depression with increased risk for adverse pregnancy and neonatal outcomes. In this study, the women who had been hospitalized for major depression had a 91 per cent higher risk of preterm delivery, compared to women with no history of mental illness. While they did not have increased risk of very large infants, they did have a 22 per cent higher risk of having an infant that was very small for its gestational age.

The study also looked at newborn health outcomes such as sepsis, neonatal abstinence syndrome and respiratory distress syndrome. Each of these conditions was significantly more common among women with bipolar disorder or major depression. Babies born to women with these mental health conditions were also more likely to be born with congenital malformations, and to be readmitted to hospital within 28 days of going home.

The study authors note that the increased perinatal risks in women with bipolar disorder are likely to be due to a number of factors, not a single issue. These factors may include:

  • the physiological effects of mental illness
  • socioeconomic and lifestyle factors that are common among women with major mood disorders
  • possible increased risks associated with medications used to treat mood disorders in pregnancy

The authors also note that because the study only looked at women with mood disorders who had been hospitalized, the results may not apply to women with less severe forms of these illnesses.

The study was published online in the American Journal of Obstetrics and Gynecology on Nov. 3, 2014.

 

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  • A publication of:
  • Women's College Hospital