She went to labor and delivery (5th month), and it was a holiday, so they were short on coverage and sent her to the er.
They monitored blood pressure, checked the baby on a monitor and did a urine sample. They said that migraines can cause restricted blood flow and lead to these type of syptoms. She had had a migraine that day, it was kind of a stressful day also. They told her that migraines are usually different during pregnancy (either better or worse than usual). They gave her baby aspirin and she hasn't had the problem since, besides slight numbness or swelling of the hands in the morning. When she later described that incident to her ob/gyn he said "did you have a migraine that day?", so he had seen it before.
She felt a headache coming on a week or so later and took another baby aspirin before any symptoms showed up.
We were pretty scared about it, but I get the idea there wasn't much they could do. It was a relief to at least have her talk to the doctor.
Good luck!