
She was pregnant (barley a baby bump going) but about the time she would actually not be able to hide the child things went wrong. The baby turned to stone and started to cause Sylvia to get sick because of some mineral thingy that can happen when the baby turns to stone. A c section was called for but on removing the baby her uterus was cut. She was sewed up before they caught the cut. So she internally bled out and died.
I know, I'm a horrible person. Kill me later.