In The Good Thief by Hannah Tinti, what happened to Ren's Mother?

The protagonist of Hannah Tinti's The Good Thief is Ren, an orphan with a missing left hand who lives in St. Anthony's orphanage until being adopted by Benjamin Nab. Ren grows up with no knowledge of his family and with the only evidence of his past being his name: the letters R-E-N had been sewn into his baby clothing when he was abandoned at the gates of the orphanage.
Ren eventually learns the true story of his family from his mother's brother, Uncle McGinty. Ren's grandfather sexually abused his daughter, Margaret (Ren's mother), which led the woman to fall into a deep depression and attempt to commit suicide several times. Later on, Margaret became pregnant with Ren and died shortly after giving birth to him.