Obstetrics: Take the Confusion Out of Pre-Existing Hypertension ICD-10-CM Coding

Hypertension is a common diagnosis, so a lot of specialties have to understand the rules for coding this condition. Obstetrics coders have to go one step further for hypertension and learn the specific rules for coding pre-existing hypertension in pregnancy, which is our focus today. 

Watch for Documentation of Pre-Existing or Gestational

You’ll find the obstetrics codes for hypertensive disorders in the O10–O16 range of ICD-10-CM. Categories O10.- Pre-existing hypertension complicating pregnancy, childbirth and the puerperium and O11.– Pre-existing hypertension with pre-eclampsia are both specific to pre-existing hypertension. 

Term tips: Pre-existing means that the mother had the condition prior to pregnancy. If you like sources for your terms, you’ll find that definition of pre-existing in section I.C.15.c of the ICD-10-CM Official Guidelines for Coding and Reporting (FY 2019). 

In contrast to the pre-existing codes, two categories in the range specify “Gestational [pregnancy-induced]”: 

• O12.- Gestational [pregnancy-induced] edema and proteinuria without hypertension

• Note that O12.- specifies “without hypertension” 

• O13.- Gestational [pregnancy-induced] hypertension without significant proteinuria

The other categories in the range include O14.- Pre-eclampsia, O15.- Eclampsia, and O16.- Unspecified maternal hypertension. Pre-eclampsia and eclampsia are disorders of pregnancy involving high blood pressure and organ damage. Kidney damage is often detected after testing for proteinuria, or urine in the blood. Eclampsia also involves seizures. 

Follow ‘Use Additional Code’ Notes for Heart and Kidney Disease

Just like in non-obstetric cases, coding for pre-existing hypertensive heart disease and kidney disease in pregnancy requires some extra care because you have to identify the type of heart or kidney disease. Check out these subcategories and the “use additional code” notes that accompany them: 

• O10.1- Pre-existing hypertensive heart disease complicating pregnancy, childbirth and the puerperium
• Use additional code from I11 to identify the type of hypertensive heart disease 

• O10.2- Pre-existing hypertensive chronic kidney disease complicating pregnancy, childbirth and the puerperium
• Use additional code from I12 to identify the type of hypertensive chronic kidney disease 

• O10.3- Pre-existing hypertensive heart and chronic kidney disease complicating pregnancy, childbirth and the puerperium
• Use additional code from I13 to identify the type of hypertensive heart and chronic kidney disease 

• O10.4- Pre-existing secondary hypertension complicating pregnancy, childbirth and the puerperium
• Use additional code from I15 to identify the type of secondary hypertension

Add O10.- When Coding O11.-

Category O11.- applies when the patient has pre-existing hypertension with pre-eclampsia. When you report a code from O11.-, you should use an additional code from O10.- to identify the type of hypertension. 

And once you use a code from O10.-, you of course need to check if that code has a “use additional code” instruction of its own, to follow the rules we went over in the previous section. 

Know Timing to Select Final Characters

To ensure accurate reporting of hypertension complicating pregnancy, you’ll need to know whether the condition complicates pregnancy (and if so which trimester), childbirth, or the puerperium. The answer will lead you to the correct additional characters required to make your code reportable and valid. 

For instance: An example of a final, complete code is O10.111 Pre-existing hypertensive heart disease complicating pregnancy, first trimester.

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Deborah Marsh

Deborah Marsh, JD, MA, CPC, CHONC, is a senior development editor at AAPC. She has explored the ins and outs of coding for multiple specialties, particularly radiology, cardiology, and oncology.

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