O21.0 Mild hyperemesis gravidarum

Billable ICD-10-CM code, FY2026.

Applicable to

• Hyperemesis gravidarum, mild or unspecified, starting before the end of the 20th week of gestation

MS-DRG index

Defines the logic of DRG(s) 817-819 in MDC 14.

Approximate ICD-9-CM (GEMs)

• 643.03 Mild hyperemesis gravidarum, antepartum condition or complication (approximate)

Medicare Code Edits (MCE v43.1 (April 2026))

• Maternity diagnoses (age 9 through 64): Age conflict edit. These diagnoses are clinically expected only in patients age 9 through 64.

Code annotations containing back-references to O21.0

Back-references to O21

• Type 1 Excludes: R11 Nausea and vomiting ("excessive vomiting in pregnancy (O21.-)")

Diagnosis Index entries for O21.0

• Hyperemesis › gravidarum (mild)
• Pregnancy (single) (uterine) › complicated by (care of) (management affected by) › hyperemesis (gravidarum) (mild)
• Pregnancy (single) (uterine) › complicated by (care of) (management affected by) › vomiting › hyperemesis gravidarum (mild)

Nearby codes

• O21 Excessive vomiting in pregnancy
• O21.0 Mild hyperemesis gravidarum (this code)
• O21.1 Hyperemesis gravidarum with metabolic disturbance
• O21.2 Late vomiting of pregnancy
• O21.8 Other vomiting complicating pregnancy
• O21.9 Vomiting of pregnancy, unspecified