O40.2XX4
Polyhydramnios, second trimester, fetus 4
O40.2XX4 (also written O402XX4) is a billable ICD-10-CM diagnosis code for polyhydramnios, second trimester, fetus 4. It is part of the FY2027 code set, effective October 1, 2026. It is one of the 28 codes in category O40 (Polyhydramnios). Its 7th character, 4, means fetus 4. Its coding notes include a Use additional code instruction, 2 Excludes1 entries and 4 Excludes2 entries.
7th character
Category O40 requires a 7th character. O40.2 has only 4 characters, so a placeholder X fills the empty positions.
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.
Home Health Primary
Accepted as the primary (principal) diagnosis on a home health claim. The Home Health Grouper assigns it to the MMTA - Other clinical group.
Source: CMS Home Health Grouper Software v07.2.26, effective October 1, 2026Includes
Further defines or gives examples of the content of the category.
- hydramnios
Notes
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