grief is a transient phenomenon while depression is a clinical term and lasts. A "normal" person has griefs while a psych person has depression and this depression is not necessarily justified.
i found you a comparison by a researcher in bipolarity Jamison where she distinguishes Grief From Depression.
My view is that a normal person when in grief there is a feedback mechanism or a thermostat by which he adjusts himself again. While for us this thermostat is broken so it can turn into a trigger which results in depression.
again with a mood disorder personality he/she will find always excuses to get depressed, even if it isn't his/her own fault, this is how the mechanism goes, regret, remorse,... this is why they commonly associate BP to BPD
Well I wouldn't rule out grief, losing a child whether born or not is hard on a parent and I'm sure it could also trigger a depressive episode in your bipolar disorder as well. It's a tough question really.
Losing a child is one of the most stressful and traumatic things that can happen to anyone. Grief is a very powerful emotion and you can have both grief and depression at the same time. Grief and depression are like brother and sister, if you will, and both can cause you to have feelings of suicide etc.
So, what you need to do is get in to talk to someone who knows about both grief and bipolar. You need to move through this process of grieving and take care of yourself and your girlfriend. You can do this together, and support each other.
I am so very sorry about your loss. :(
I'm sorry to hear about your girlfriend's miscarriage. Grief and depression can feel very similar, but also very different at the same time in my experience. It's raw and powerfully overwhelming, inescapable. Depression for me, at least, is numb and lifeless, a void of emotion rather an a devastating flood of emotion.
Like the other posters said, it's very possible that what you're feeling right now is a natural grieving response to a major loss. Remember that feeling grief is entirely, completely normal. It isn't an uncommon thing for people in grief to feel so far gone that suicide becomes a real option in their minds. Please be safe right now, and reach out to people around you if you can to maintain a support network to see you through this difficult time. It sounds like you are aware of these feelings, and it's good that you are considering calling a helpline if they get to a dangerous point.
Unfortunately, major losses like this can potentially trigger episodes in people with mood disorders, and it's a possibility that you could slide into a depression that goes beyond grief. Remember, however, this is not to say that you are definitively going to become depressed. You just need to remind yourself that what you are feeling now is normal, and you need to give yourself time and space to process the loss, and to eventually heal from it.
I agree with the others, grief is natural under the circumstances. The loss of the child is an understandable cause of grief. However, grief can cause you to slip into depression, and stay there. (I know, I've been there.)
I don't know your religion, but in Buddhism, there's a statue called a jizo that is meant to represent a lost child. The jizo is a way to maintain contact with the lost child, while acknowledging that their soul is on a new path. It can really help to have something to symbolize the child that you can see, and honor. Anyway, it just a suggestion.
Good luck during this hardship,