O11.9 Pre-existing hypertension with pre-eclampsia, unspecified trimester

Billable ICD-10-CM code, FY2026.

Applies from O11 Pre-existing hypertension with pre-eclampsia

Includes

• conditions in O10 complicated by pre-eclampsia
• pre-eclampsia superimposed pre-existing hypertension

Use additional code

• code from O10 to identify the type of hypertension

MS-DRG index

Defines the logic of DRG(s) 817-819 in MDC 14.

Approximate ICD-9-CM (GEMs)

• 642.20 Other pre-existing hypertension complicating pregnancy, childbirth, and the puerperium, unspecified as to episode of care or not applicable (approximate)
• 642.70 Pre-eclampsia or eclampsia superimposed on pre-existing hypertension, unspecified as to episode of care or not applicable (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Maternity diagnoses (age 9 through 64): Age conflict edit. These diagnoses are clinically expected only in patients age 9 through 64.

Code annotations containing back-references to O11.9

Back-references to O11

• Type 1 Excludes: I10 Essential (primary) hypertension ("hypertensive disease complicating pregnancy, childbirth and the puerperium (O10-O11, O13-O16)")
• Type 2 Excludes: O10 Pre-existing hypertension complicating pregnancy, childbirth and the puerperium ("pre-existing hypertension with superimposed pre-eclampsia complicating pregnancy, childbirth and the puerperium (O11.-)")
• Type 1 Excludes: O14 Pre-eclampsia ("pre-existing hypertension with pre-eclampsia (O11)")
• Type 2 Excludes: O99.4 Diseases of the circulatory system complicating pregnancy, childbirth and the puerperium ("hypertensive disorders (O10-O16)")

Nearby codes

• O11.1 Pre-existing hypertension with pre-eclampsia, first trimester
• O11.2 Pre-existing hypertension with pre-eclampsia, second trimester
• O11.3 Pre-existing hypertension with pre-eclampsia, third trimester
• O11.4 Pre-existing hypertension with pre-eclampsia, complicating childbirth
• O11.5 Pre-existing hypertension with pre-eclampsia, complicating the puerperium
• O11.9 Pre-existing hypertension with pre-eclampsia, unspecified trimester (this code)