Headache in Pregnancy ICD-10 Code: O99.891

The ICD-10 code for headache in pregnancy is O99.891 (first trimester), O99.892 (second trimester), or O99.893 (third trimester) - Other specified diseases and conditions complicating pregnancy.

Why Use O Chapter Codes?

When a pregnant patient presents with a condition that complicates pregnancy, use Chapter 15 (O codes) rather than symptom codes. This follows the ICD-10-CM guideline that pregnancy codes take precedence when the condition affects or is affected by the pregnancy.

Key principle: Simple headache during pregnancy is coded with O99.89x, not R51.9 (Headache, unspecified). The O code tells payers and providers that the patient is pregnant and the condition is being managed in that context.

Trimester Selection

If trimester isn't specified, use O99.899 (unspecified trimester).

When to Use Different Codes

Not all headaches in pregnancy use O99.89x. The code depends on the underlying cause:

Critical: Headache is a warning sign for pre-eclampsia. If the patient has elevated blood pressure or other pre-eclampsia findings, code the pre-eclampsia (O14.x), not just O99.89x.

Common Coding Scenarios

Scenario 1: Simple Headache at 28 Weeks

Documentation: "28 weeks pregnant with frontal headache for 2 days. BP normal, no visual changes, no proteinuria."

Code: O99.893 (Other specified diseases and conditions complicating pregnancy, third trimester)

Rationale: Simple headache in pregnancy without pre-eclampsia features. Use third trimester code for 28 weeks.

Scenario 2: Migraine in Pregnancy

Documentation: "Migraine without aura in second trimester pregnancy. Discussed medication safety."

Codes:

• O99.892 (Other conditions complicating pregnancy, second trimester)
• G43.009 (Migraine without aura, not intractable, without status migrainosus)

Rationale: Code both the pregnancy complication code and the specific type of migraine for complete capture.

Scenario 3: Headache Concerning for Pre-eclampsia

Documentation: "36 weeks with severe headache, BP 158/102, 2+ proteinuria. Pre-eclampsia with severe features."

Code: O14.13 (Pre-eclampsia with severe features, third trimester)

Rationale: When pre-eclampsia is diagnosed, code the pre-eclampsia - the headache is a symptom of the pre-eclampsia, not a separate condition.

Scenario 4: Headache with Normal Workup

Documentation: "20 weeks pregnant, headache. BP 118/70, urinalysis negative, no visual symptoms. Likely tension headache. Advised acetaminophen."

Code: O99.892 (Other specified diseases and conditions complicating pregnancy, second trimester)

Rationale: After ruling out pre-eclampsia, code as other specified condition complicating pregnancy.

Don't Use These Codes Alone

During pregnancy, avoid using these as primary codes without the O chapter code:

• R51.9 - Headache, unspecified
• R51.0 - Headache with orthostatic component
• G43.x - Migraine codes alone

These may be used as secondary codes to provide specificity about the type of headache, but the O99.89x code should be primary to capture the pregnancy context.

Red Flag Headaches in Pregnancy

Always evaluate for serious causes before coding as simple headache:

• Pre-eclampsia/eclampsia - elevated BP, proteinuria, neurologic symptoms
• Cerebral venous thrombosis - especially postpartum
• Posterior reversible encephalopathy syndrome (PRES)
• Pituitary apoplexy - sudden severe headache postpartum

If any of these are diagnosed, use the specific condition code rather than O99.89x.