I'm sorry, but as someone who is bipolar, it is impossible for for pregnancy to cause bipolar disorder. Bipolar disorder either already affected you and your pregnancy made it worse, or you are wrong yourself or somehow misdiagnosed. Severe depression, mood things, hallucinations etc are not remotely the same as being bipolar, even with "mania" (read: not mania just because you're hyper/anxious/very energetic etc). It's very very VERY commonly misdiagnosed (at least in the US) because some psychiatrists don't know exactly what bipolar symptoms look like an opposed to other stuff. Patients are given a new diagnosis once they present symptoms showing a different mental illness being more likely and/or once certain bipolar symptoms never present themselves.