Coding for Obstetrical Services in ICD-10 requires additional information over what was necessary for coding in ICD-9. The majority of codes in the Obstetrics Chapter include a character, either in the 6th position or final position, to identify the trimester or number of weeks of pregnancy. Each category that involves the use of a digit for “trimester” includes a code for “unspecified trimester,” but this should rarely be reported because the documentation should indicate the trimester involved, per the coding guidelines in ICD-10.

Official Guidelines for Coding and Reporting (OGCR) provides additional instruction: “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.”

The following is an example of how the trimester determines the ICD-10 that’s reported:

Example 1: Pregnancy_complicated by_decreased fetal movement 036.8-

  • Decreased fetal movements – O36.81_
    • O36.812_ - second trimester
    • O36.813_ - third trimester
    • O36.819_ - unspecified trimester
    • 7th character defines fetus involved

Per the ICD-10 chapter 15 (15.a.3) guidelines, the trimester timeframes are as follows:

  • 1st Trimester – less than 14 weeks, 0 days
  • 2nd Trimester – 14 weeks 0 days to less than 28 weeks 0 days
  • 3rd Trimester – 28 weeks 0 days to delivery
  • Weeks of Gestation (appended to certain codes from another chapter)

In addition to the trimester in the above example, a 7th character will need assigned to describe the fetus involved:

  • 0=not applicable or unspecified
  • 1=fetus 1
  • 2=fetus 2
  • 3=fetus 3
  • 4=fetus 4
  • 5=fetus 5
  • 9=other fetus

This change is applicable to categories O31, O32, O33.3-O33.6, O35, O36, O40, O41, O60.1, O60.2, O64 and O69, and is used to identify the fetus for which the complication code applies.

Generally, all pregnancy related services are reported with a code from Chapter 15 (15.a.1); however, if the provider of the service indicates the pregnancy is incidental, the OGCR guidelines would be followed for reporting the service:

          Codes from chapter 15 and sequencing priority instruction: "Obstetric cases require codes from chapter 15, codes in the range O00-O9A, Pregnancy, Childbirth, and the Puerperium. Chapter 15 codes have sequencing priority over codes from other chapters. Additional codes from other chapters may be used in conjunction with chapter 15 codes to further specify conditions. Should the provider document that the pregnancy is incidental to the encounter, then code Z33.1, Pregnant state, incidental, should be used in place of any chapter 15 codes. It is the provider’s responsibility to state that the condition being treated is not affecting the pregnancy."


Reference: ICD-10-CM Official Guidelines for Coding and Reporting
 FY 2016 Chapter 15: Pregnancy, Childbirth, and the Puerperium

Author - Female

About the author

Myra Blankenship, CIRCC, CPC of Compliance-Radiology, McKesson Business Performance Services.