Q91 – Trisomy 18 and Trisomy 13
ICD-10-CM 2027 diagnosis code · Chromosomal abnormalities, not elsewhere classified
ICD-10-CM code
Q91
- Code
Q91(claims format:Q91)- Description
- Trisomy 18 and Trisomy 13
- Billable
- No – use a more specific code below
- Valid for
- Dates of service October 1, 2026 – September 30, 2027 (FY2027)
- Chapter
- 17. Congenital malformations, deformations, chromosomal abnormalities, and genetic disorders (Q00-QA1)
- Block
- Q90-Q99 Chromosomal abnormalities, not elsewhere classified
Billable codes under Q91
Q91 is a header code and cannot be used on claims. Choose the most specific code:
- Q91.0 – Trisomy 18, nonmosaicism (meiotic nondisjunction)Billable
- Q91.1 – Trisomy 18, mosaicism (mitotic nondisjunction)Billable
- Q91.2 – Trisomy 18, translocationBillable
- Q91.3 – Trisomy 18, unspecifiedBillable
- Q91.4 – Trisomy 13, nonmosaicism (meiotic nondisjunction)Billable
- Q91.5 – Trisomy 13, mosaicism (mitotic nondisjunction)Billable
- Q91.6 – Trisomy 13, translocationBillable
- Q91.7 – Trisomy 13, unspecifiedBillable
Notes inherited from parent codes
Instructional notes at a category or block level apply to every code below it.
Block Q90-Q99
Excludes2 (not included here):
- mitochondrial metabolic disorders (E88.4-)
Frequently asked questions
What is ICD-10 code Q91?
Q91 is the ICD-10-CM code for trisomy 18 and Trisomy 13, in the block Q90-Q99 (Chromosomal abnormalities, not elsewhere classified).
Is Q91 a billable code?
No. Q91 is a header code with more specific child codes; report one of the billable codes listed above.
Source: CDC/NCHS ICD-10-CM FY2027 code files, tabular list and index. Reference only – code assignment must follow the official ICD-10-CM guidelines and documentation in the medical record.