I Would Like Some Facts Concerning Hep C. My Sister

I would like some facts concerning Hep C. My sister in law was recently diagnosed and became pregnant shortly after, during the beginning of the pregnancy they did a viral load test for the Hep C and it came back negative. Her pregnancy has been perfectly normal the only problem has been her feet and lower legs began to swell really bad. She was 18 weeks and 5 days last Thursday and was admitted in the hospital only to deliver the baby early and it didn't survive. She is still in the hospital and the doctors say the fluid from her feet and legs traveled up to her stomach and is now around her heart. Is there anything you can tell me about what might be wrong?