Final character for trimester

The majority of codes in Chapter 15 have a final character indicating the trimester of pregnancy. The timeframes for the trimesters are indicated at the beginning of the chapter. 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.

Certain codes have characters for only certain trimesters because the condition does not occur in all trimesters, but it may occur in more than just one. Assignment of the final character for trimester should be based on the provider’s documentation of the trimester (or number of weeks) for the current admission/encounter.

This applies to the assignment of trimester for pre-existing conditions as well as those that develop during or are due to the pregnancy. The provider’s documentation of the number of weeks may be used to assign the appropriate code identifying the trimester.

Whenever delivery occurs during the current admission, and there is an “in childbirth” option for the obstetric complication being coded, the “in childbirth” code should be assigned. When the classification does not provide an obstetric code with an “in childbirth” option, it is appropriate to assign a code describing the current trimester.