Identifying Trimester Coding in ICD-10 - Replaces previous tip from 2015
In ICD-10 trimester-based coding is utilized to identify the trimester during the encounter. Instructions about obstetric trimester-based billing is found in Chapter 15. The CMS and the NCHS (within the US Federal Government’s DHHS) provides these instructions in their ICD-10 CM manual. The ICD-10-CM is based on the ICD-10, the statistical classification of disease published by the WHO. These guidelines have been approved by the four organizations that make up the Cooperating Parties for the ICD-10-CM: the American Hospital Association (AHA), the American Health Information Management Association (AHIMA), CMS, and NCHS.
The majority of codes in Chapter 15 have a final character indicating the trimester of pregnancy. If trimester is NOT a component of a code it is because the condition always occurs in a specific trimester, or the concept of trimester of pregnancy is not applicable. Assignment of this final character for trimester should be based on the providers documentation of the trimester (or number of weeks) for the current admission or date of encounter.
Per the ICD-10 manual, there is a notation specifically ONLY about inpatient admissions (suggesting a differentiation when billing as an outpatient, though there is no specific verbiage to acknowledge that):
1) Outpatient Coding
The SMFM Coding Committee since 2015 has stated that for services provided in an outpatient setting, the ICD-10 trimester character is assigned based on the gestational age at the TIME OF THE ENCOUNTER. The Z3A.XX codes also reflect the completed gestational weeks at the TIME OF THE ENCOUNTER. Presumably this then means that you will CHANGE your trimester-based codes to reflect where you are in the pregnancy at the time of the visit on that date of service.
2) Inpatient Coding
In instances where a patient is admitted to a hospital for complications of pregnancy during one trimester and then remains in the hospital into the next trimester, the coding reflects the basis of the trimester when the complication developed (NOT the trimester of discharge or Date of service). If the entirety of the stay encompasses a single trimester, then the coding would reflect only that trimester. So, you assign the character for the trimester at the TIME OF THE ADMISSION, and then do NOT change it for the length of stay despite when you round, when the patient delivers, when she is discharged. If the condition developed during the admission, code the trimester in which the condition developed and then again do NOT change it for the length of stay. Further the manual states that for Z3A.XX codes that the date of the admission should be used to determine weeks of gestation for inpatient admissions that encompass more than one gestational week.
For example:
Andrea is admitted at 27 weeks 2 days with pre-existing chronic hypertension and preeclampsia.
Code: O10.012 (Pre-existing essential hypertension, 2nd trimester)
Code: O11.2 (Pre-existing essential hypertension with preeclampsia, 2nd trimester)
Code: Z3A.27 (27 weeks at the time of admission)
Now, 2 weeks later, you are again rounding on her as she has remained in the hospital for these conditions. Today, at 29 weeks 2 days your coding would remain as follows even though you are in the 3rd trimester now:
Code: O10.012 (Pre-existing essential hypertension, 2nd trimester)
Code: O11.2 (Pre-existing essential hypertension with preeclampsia, 2nd trimester)
Code: Z3A.27 (even though she is 29 week today at the time of the visit)
Even though Andrea is in the 3rd trimester, she is in the hospital, which means inpatient billing rules apply. The codes for her conditions have a 2nd trimester character as this is when the condition was present at the time of her initial admission. Some payers may have coding edits in place that prevent a second trimester code being used with a third trimester code on the same claim. As always, the committee recommends you submit the diagnoses required to facilitate appropriate claim payment regardless of the ICD-10-CM guidelines in these scenarios.
This situation above becomes more complex when you consider delivery. ICD-10-CM guidelines state that whenever delivery occurs during the current admission and there is an ‘in-childbirth’ option for the obstetric complication being coded that the ‘in-childbirth’ code be assigned. Many patients are inpatient status for quite some time, as in our example above, prior to delivery. Interim billing for inpatient services can take place prior to the delivery by facilities. If the patient is in the 3rd trimester and an interim bill is submitted, then following the coding above is appropriate. If the biller knows the patient has delivered at the time of the claim/billing, then it may be more appropriate to use the ‘in-childbirth’ code (O10.02 – pre-existing hypertension delivery).