Tip: Over 42 weeks means you should opt for “prolonged” code. Patients whose pregnancies last longer than 40 weeks gestation are either labeled “post term pregnancies” (40-42 weeks) or “prolonged pregnancies” (over 42 weeks).  ICD-9-CM Codes: Currently, you should report this condition with the following diagnosis codes: 645.10, Post term pregnancy, unspecified episode of care  645.11, ... delivered, with or [...]