Final answer:
The diagnosis codes for the given condition are Z3A.20, O09.03, and O10.03.
Step-by-step explanation:
The diagnosis code(s) for a 20-week pregnancy with low weight gain and pre-existing essential hypertension complicating the pregnancy would be:
- Code Z3A.20 for 20-week pregnancy
- Code O09.03 for low weight gain during pregnancy
- Code O10.03 for pre-existing essential hypertension complicating the pregnancy
These codes are used in medical documentation to accurately describe the patient's condition and ensure proper billing and healthcare management.