O41.1029
Infection of amniotic sac and membranes, unspecified, second trimester, other fetus
O41.1029 (also written O411029) is a billable ICD-10-CM diagnosis code for infection of amniotic sac and membranes, unspecified, second trimester, other fetus. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 168 codes in category O41 (Other disorders of amniotic fluid and membranes). Its 7th character, 9, means other fetus. Its coding notes include a Use additional code instruction, 2 Excludes1 entries and 4 Excludes2 entries.
7th character
Category O41 requires a 7th character.
Guidelines tip
From the FY2027 Official Guidelines. ICD10Ref adds no rules of its own.
The trimester character comes from the provider's documentation for the current encounter. The unspecified trimester code should rarely be used.
Use additional code
Add the listed code as a secondary code, if known.
Also from chapter/block level (1 note)
- code, if applicable, from category Z3A, Weeks of gestation, to identify the specific week of the pregnancy, if known.
Excludes1
Not coded here. The listed conditions generally should not be reported together.
- encounter for suspected maternal and fetal conditions ruled out (Z03.7-)
Also from chapter/block level (1 note)
- supervision of normal pregnancy (Z34.-)
Excludes2
Not included here. Both codes may be reported if the patient has both conditions.
Also from chapter/block level (4 notes)
Care settings
How CMS programs treat this code. These are CMS claim edits and list entries, not coverage or eligibility rules.
Hospital MCC
Counts as a major complication or comorbidity (MCC) when reported as a secondary diagnosis on an inpatient claim. It does not count when the principal diagnosis is one of the 63 codes in its exclusion list. Some MS-DRGs also ignore a CC or MCC that defines the DRG.
Source: CMS MS-DRG Definitions Manual v44, effective October 1, 2026, Appendix CNotes
Also from chapter/block level (6 notes)
- CODES FROM THIS CHAPTER ARE FOR USE ONLY ON MATERNAL RECORDS, NEVER ON NEWBORN RECORDS
- Codes from this chapter are for use for conditions related to or aggravated by the pregnancy, childbirth, or by the puerperium (maternal causes or obstetric causes)
- Trimesters are counted from the first day of the last menstrual period. They are defined 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 until delivery