Mass General Hospital

Harvard Medical School

What’s Worse for Pregnancy: Bipolar Disorder or the Medications Used to Treat It?

In studies of pregnant women with unipolar depression, it has been shown that untreated psychiatric illness in the mother may have a negative impact on pregnancy outcomes, influencing the length of gestation and birthweight.  There is far less data on pregnancy outcomes in women with bipolar disorder.  A recent Swedish study analyzes pregnancy outcomes in treated and untreated women with bipolar disorder and attempts to distinguish between the effects of medication versus the effects of untreated psychiatric illness in the mother.

In this population-based cohort study, women with a recorded diagnosis of bipolar disorder were identified.  Treated women (n=320) were those women who had filled at least one prescription for a mood stabilizer (lithium, antipsychotics, or anticonvulsants) during pregnancy.  Also included was a group of untreated women with bipolar disorder (n=554). Outcomes were compared with all other women giving birth (n=331,263).  Data was derived from three national health registries.  Outcomes of interest included preterm birth, mode of labor induction, gestational diabetes, infants born small or large for gestational age, neonatal morbidity, and congenital malformations.

In general, pregnancy outcomes were worse in women with bipolar disorder:

  • Women with bipolar disorder were more often induced or had a planned caesarean section compared to women without bipolar disorder.  The corresponding rates were 30.9% (n=171) in the untreated women (odds ratio [OR] = 1.57) and 37.5% (n=120) in the treated women (OR=2.12).

  • Risk of preterm birth was increased by 50% in both treated and untreated women.
  • Microcephalic infants were more commonly born to women with bipolar disorder: 3.3% of the treated women (n=311, OR=1.26) and 3.9% of the untreated women (n=542, OR=1.68) versus 2.3% of the women without bipolar disorder.
  • Similar trends were observed for risks of infants being small for gestational age and having lower birth weight and length.

The authors conclude that bipolar disorder in women, whether treated or not, was associated with worse pregnancy outcomes.  While this study is one of the largest to address questions regarding the impact of illness on outcomes, it does have some limitations.  First of all, do the women who receive treatment differ in any way from the women who do not?  And there are other factors which may influence outcomes.  For example, mothers with bipolar disorder were more often smokers, overweight and abusers of alcohol or illicit substances than unaffected mothers.  Nonetheless, the study suggests that exposure to mood stabilizers is not the sole reason for adverse pregnancy outcomes in women with bipolar disorder, and the illness itself – or behaviors associated with the having the illness – may also have an effect on pregnancy outcomes.

In an accompanying editorial, Dr. Salvatore Gentile highlights the importance of optimizing the treatment of women with bipolar disorder during pregnancy, stating that the avoidance of all medications is not necessarily the safest option.  Women planning a pregnancy must be properly counseled regarding the risks of treatment versus the risks associated with the untreated psychiatric illness in the mother, and the woman’s health care provider plays an important role in weighing these individual risks and selecting the best options for treatment.

Ruta Nonacs, MD PhD

Boden R et al. Risks of adverse pregnancy and birth outcomes in women treated or not treated with mood stabilisers for bipolar disorder: Population based cohort study. BMJ 2012; 345:e7085.

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