A recently published article in the prestigious British Medical Journal has demonstrated that there are no significant differences in adverse pregnancy and birth outcomes in treated versus untreated women with bipolar disorder; this is an important piece of empirical information for clinicians tasked with the onerous responsibility of weighing the risks and benefits of prescribing bipolar medication during pregnancy.
That said, this particular study was unable to assess the risk of medication related malformations; these have been described and fully documented in many other major studies. However, the study did clearly demonstrate, in line with other studies, that women diagnosed with bipolar disorder had worse pregnancy outcomes than women who did not have the condition.
You can read an excellent summary of the article here. Or, you can read the entire article here: 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 Nov 8; 345:e7085. (http://dx.doi.org/10.1136/bmj.e7085)