N91.1Secondary amenorrhoea
Code usage status
Primary diagnosis
May be used as the primary diagnosis
Apply only when it matches the confirmed diagnosis and the documented clinical record.
Specificity
Complete code in the classification
Use when the diagnosis matches and no exclusion applies.
- Chapter XIV
- Diseases of the genitourinary system
- Group N80-N98
- Noninflammatory disorders of female genital tract
- Official Vietnamese name
- Vô kinh thứ phát
- Additional WHO coding guidance
- Absence of menstruation in a woman who had
Related N91 codes
N91
Absent, scanty and rare menstruation
N91.0
Primary diagnosis candidate
Primary amenorrhoea
N91.2
Primary diagnosis candidate
Amenorrhoea, unspecified
N91.3
Primary diagnosis candidate
Primary oligomenorrhoea
N91.4
Primary diagnosis candidate
Secondary oligomenorrhoea
N91.5
Primary diagnosis candidate
Oligomenorrhoea, unspecified
Clinical record checklist
View coding guide →- Confirm that the code matches the final documented diagnosis.
- Use one primary-diagnosis code and record only relevant additional conditions.
- Review Ministry indicators, inclusions, exclusions and notes.
- Do not infer a diagnosis beyond the clinical record.
2026 regulatory basis
Indicators are taken from columns 24–29 of the classification accompanying Circular 06/2026/TT-BYT, cross-referenced with Decision 1849/QĐ-BYT and Official Dispatch 4059/BYT-BH.
