Deputies said they found 22-year-old Courtney Quintana, who was 20 weeks pregnant, severely beaten.
The baby died that night at the hospital.
Authorities said Cunningham assaulted Quintana after a heated argument.
Cunningham is charged with capital murder, but Montague County District Attorney Jack McGaughey said even if a death sentence is recommended during the jury's deliberations, he doesn't believe it would be upheld during the appeals process because of Cunningham's lack of prior criminal convictions.
McGaughey said his office will seek life without parole.
Copyright 2016 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.