Pre-existing hypertension with pre-eclampsia, unsp trimester

This code signifies a pregnancy complicated by the development of pre-eclampsia in a patient who had pre-existing hypertension prior to conception. It indicates a superimposed pre-eclampsia without specifying the severity or specific trimester of onset or diagnosis.

Use this code when documentation clearly states "pre-existing hypertension with pre-eclampsia" or "superimposed pre-eclampsia on chronic hypertension" without further specification of the trimester. This code is appropriate when the medical record confirms a history of hypertension predating the current pregnancy and the subsequent development of pre-eclampsia.

• Do not use this code if the pre-eclampsia is specified as mild or severe; instead, use the more specific codes within O11.x.
• Always sequence this code as the principal diagnosis if it is the main reason for the encounter, followed by codes for any associated manifestations.
• Ensure documentation differentiates between gestational hypertension, pre-existing hypertension, and pre-eclampsia to avoid miscoding.