That sounds like a scary thing to happen. Did she lose total vision? Or just part of her vision? Did she have any headaches? Does she have any other medical condition? Is this her first pregnancy?
This is a very odd situation. The MRI/MRA ruled out strokes, aneurysms. Only systemic problems can result is loss of vision in both eyes. Problems like low blood sugar, low blood pressure, blood loss, electrolyte imbalances. All of these would have also been ruled out in the hospital. Specific eye problems (like bleeding, stroke to the eyes, retinal detachment, inflammation) usually only affect one eye. She needs a good neurologic examination (I assumed that was done in the hospital). She also needs a good eye examination (I don't know if that has been done or not).
If all of these are normal, I must tell you (and you may not like to hear this) that the remaining diagnosis would be anxiety and/or hysterical vision loss (we call it physiologic vision loss).
Hope this helps.
After you have ruled out everything else, you are left with this. Physiologically, it is virtually impossible to lose total vision in both eyes simultaneously.
Symptoms of anxiety and/or conversion reaction usually cannot be predicted. These are not symptoms just from stress (that we all normally feel at times). These are real symptoms that have their cause in a psychologic condition. She really cannot see, but there is no structural damage to her eyes or brain. Psychologically, she cannot see.
How to treat it is more difficult. You can't just send the patient to see a psychiatrist. If they think that there is nothing wrong, that can be a turn off in terms of their healing. She needs lots of support and empathy. You may need to discuss this honestly with the doctors and try to come up with ways to help her. Find out what else is going on other than have her first baby (was there anything wrong with the last OB exam? is there friction or stress between her and the father? or his family? or your family? find out how she feels about being pregnant).
I sincerely XXXXX XXXXX you all find a solution.