In 50 to 80% of cases, bipolar disorder is the biggest risk factor, the researchers found. Bipolar disorder, which includes symptoms such as mania, insomnia, engaging in impulsive behavior, and racing thoughts, affects 2.6% of the population, or about six million American Adults, according to the National Institute of Mental Health. (Sadly, there is no gender breakdown of the data, so it’s hard to say how many of these are women. But other research suggests bipolar disorder is indeed more common in women than in men.)For women who are aware of their bipolar disorder before and during pregnancy, knowing they’re at risk for postpartum psychosis can be a good thing, because it allows them and their families to at least be prepared for the possibility.This is why it’s so important for all pregnant women to share their mental health histories with their obstetricians and midwives — and and to work with their doctors to balance the pros and cons of continuing their medications during pregnancy, Dr. Wisner says.However, despite how relatively common it is — "Everyone knows someone with bipolar disorder," Dr. Wisner adds — many women are totally unaware they have it. That means that some women who experience postpartum psychosis don’t receive their bipolar diagnosis until after they have a psychotic episode triggered by pregnancy and birth.Unless you are already diagnosed with bipolar, the best thing you can do right now is to simply be aware (and make sure your loved ones are aware) that it can happen. This increases the likelihood that you’ll get the help you need ASAP (before it turns dangerous), should it happen to you.If you know you have bipolar disorder, on the other hand, you can ease your risk of developing postpartum psychosis by continuing to take your medication (under your doctor’s care) throughout pregnancy and while breast-feeding. This remains — quite literally — a scary pill to swallow for many mothers with mental illness, because of the question of safety.And it’s true: There are no easy answers. There’s a huge debate in the medical community about the safety of taking antidepressant and antipsychotic medication during pregnancy and the postpartum period. Many new mothers fear that the medicine will harm the baby’s growth and development, and since there is a dearth of large, long-term studies on the topic, it’s hard to say for sure what the effects will be.