Fetal Demise

We have a patient that came in and she was 24 weeks 6 days and we couldn't hear a heart beat. So we sent her for an ultrasound and the ultrasound said it was fetal demise at 21 weeks 1 day. She had to deliver the baby and I was wondering do we bill it as 24 weeks 6 days or at the 21 weeks 1 day. Thank you