Its happen with my female also , I tell you the fact -" yep poor nutrition is main reason but I thing very impt which I did, as if babies are more in no. Mother gets tired n don't puncture the balloon in which babies get outside ( kind of very sticky layer of white skin) than babies died of no oxygen,when isaw that I puncture it myself n aftr few minutes baby start breathing.its good if delivery get into front of you.
My giena pig just had baby but she didn't look pregnet but she was in a cage with others I don't know who the mother is
There are many problems when they give birth it was probably the age or poor diet many baby pigs die from it or you touched her to much