Building an ICD-10 cheat sheet for obstetrics

In my previous blog in this continuing series, I introduced two principles for building less bulky, more useful ICD-10 based cheat sheets. They are:

  • Apply the 80/20 rule.
  • Take advantage of recurring code patterns.

I am going to show you how these principles can be applied to make a much smaller ICD-10 cheat sheet for coding obstetrics encounters. The number of codes in the ICD-10 obstetrics chapter is about double: There are 1,104 ICD-9 codes and 2,155 ICD-10 codes. The vast majority of that increase comes from the application of a new level of detail across a broad range of codes. The increase can be easily managed here by ignoring the codes you don’t use much, just as you do in ICD-9 (80/20 rule), and by exploiting the regularity in the code structure itself to cut down on the number of individual codes you list on the sheet (recurring code patterns).

The 80/20 rule in obstetrics is easily applied to the codes describing maternal care for fetal problems, for example in the subcategory, O36.80 Pregnancy with inconclusive fetal viability. An additional character (think of it as a required modifier) has been added to such codes to catalogue which fetus is the focus of attention when the pregnancy is a multiple gestation. This results in significant fatty infiltration of the classification. When this additional information is applied across the board to create the codes, our example looks like this:

O36.80X0 Pregnancy with inconclusive fetal viability, not applicable or unspecified

O36.80X1 Pregnancy with inconclusive fetal viability, fetus 1 
O36.80X2 Pregnancy with inconclusive fetal viability, fetus 2 
O36.80X3 Pregnancy with inconclusive fetal viability, fetus 3 
O36.80X4 Pregnancy with inconclusive fetal viability, fetus 4 
O36.80X5 Pregnancy with inconclusive fetal viability, fetus 5 
O36.80X9 Pregnancy with inconclusive fetal viability, other fetus 

The obvious good news is that applying the 80/20 rule to such codes means only the first code in the series, the “not applicable or unspecified” option, needs to be included on your cheat sheet. You don’t want to lard up your cheat sheet with codes you will use only rarely, when the pregnancy is a multiple gestation, and you are tracking a condition that applies to a specific fetus.

Taking advantage of recurring code patterns in the obstetrics chapter is practically "textbook easy" to do. You may have heard that the main difference between coding obstetrics in ICD-9 and ICD-10 is that ICD-9 classifies patients according to whether or not they delivered during the encounter, like so…

642.30 Transient hypertension of pregnancy, unspecified as to episode of care or not applicable 
642.31 Transient hypertension of pregnancy, delivered, with or without mention of antepartum condition 
642.32 Transient hypertension of pregnancy, delivered, with mention of postpartum complication 
642.33 Transient hypertension of pregnancy, antepartum condition or complication 
642.34 Transient hypertension of pregnancy, postpartum condition or complication

Whereas, ICD-10 classifies patients according to the trimester of the pregnancy on the date of the encounter, like so…

O13.9 Gestational [pregnancy-induced] hypertension without significant proteinuria, unspecified trimester 
O13.1 Gestational [pregnancy-induced] hypertension without significant proteinuria, first trimester 
O13.2 Gestational [pregnancy-induced] hypertension without significant proteinuria, second trimester 
O13.3 Gestational [pregnancy-induced] hypertension without significant proteinuria, third trimester

Instead of listing each trimester out as a separate code on your cheat sheet, you can list these as a modifier, and state the applicable range. For example, for the final character of codes in range O09-O30:

First trimester = 1
Second trimester = 2
Third trimester = 3

Note that I did not include the option for “unspecified trimester.” I trust you have more self-respect than that. In my coding experience, pregnancies are always documented by weeks of gestation, but I have no doubt you can do the weeks to trimester calculation in your sleep, and if someone else does the coding in your office, you can provide them the necessary cross-reference.

OB/GYN specialists, I realize I talked only about cheat sheet stuff here, and not at all about differences in terminology and emphasis in OB and GYN coding for ICD-10. So I owe you one, and that will be my next blog.

Rhonda Butler is a senior clinical research analyst with 3M Health Information Systems. She is responsible for the development and maintenance of the ICD-10 Procedure Coding System since 2003 under contract to CMS, and for the development and maintenance of the ICD-10 General Equivalence Mappings (GEMs) and Reimbursement Mappings under contract to CMS and the CDC.  She leads the 3M test project to convert the MS-DRGs to ICD-10 for CMS, and is on the team to convert 3M APR-DRGs to ICD-10. Rhonda also writes for the 3M Health Information Systems blog.