O36.0921 Maternal care for other rhesus isoimmunization, second trimester, fetus 1

Billable ICD-10-CM code, FY2026.

Built from O36.092 with 7th character 1 (fetus 1).

Applies from O36 Maternal care for other fetal problems

Includes

• the listed conditions in the fetus as a reason for hospitalization or other obstetric care of the mother, or for termination of pregnancy

Excludes1 (never code together)

• encounter for suspected maternal and fetal conditions ruled out (Z03.7-)
• placental transfusion syndromes (O43.0-)

Excludes2 (not included here)

• labor and delivery complicated by fetal stress (O77.-)

7th character note

• One of the following 7th characters is to be assigned to each code under category O36. 7th character 0 is for single gestations and multiple gestations where the fetus is unspecified. 7th characters 1 through 9 are for cases of multiple gestations to identify the fetus for which the code applies. The appropriate code from category O30, Multiple gestation, must also be assigned when assigning a code from category O36 that has a 7th character of 1 through 9.

7th character required

• 0 — not applicable or unspecified
• 1 — fetus 1
• 2 — fetus 2
• 3 — fetus 3
• 4 — fetus 4
• 5 — fetus 5
• 9 — other fetus

Applies from O36.0 Maternal care for rhesus isoimmunization

Applicable to

• Maternal care for Rh incompatibility (with hydrops fetalis)

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 O36.0921

Back-references to O36.0

• Type 1 Excludes: O36.2 Maternal care for hydrops fetalis ("hydrops fetalis associated with rhesus isoimmunization (O36.0-)")
• Type 1 Excludes: R76.0 Raised antibody titer ("isoimmunization in pregnancy (O36.0-O36.1)")

Back-references to O36

• Type 2 Excludes: O98 Maternal infectious and parasitic diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium ("when the reason for maternal care is that the disease is known or suspected to have affected the fetus (O35-O36)")
• Type 2 Excludes: O99 Other maternal diseases classifiable elsewhere but complicating pregnancy, childbirth and the puerperium ("when the reason for maternal care is that the condition is known or suspected to have affected the fetus (O35-O36)")
• Type 1 Excludes: Z03.7 Encounter for suspected maternal and fetal conditions ruled out ("known or suspected fetal anomalies affecting management of mother, not ruled out (O26.-, O35.-, O36.-, O40.-, O41.-)")

Nearby codes

• O36.0914 Maternal care for other rhesus isoimmunization, first trimester, fetus 4
• O36.0915 Maternal care for other rhesus isoimmunization, first trimester, fetus 5
• O36.0919 Maternal care for other rhesus isoimmunization, first trimester, other fetus
• O36.092 Maternal care for other rhesus isoimmunization, second trimester
• O36.0920 Maternal care for other rhesus isoimmunization, second trimester, not applicable or unspecified
• O36.0921 Maternal care for other rhesus isoimmunization, second trimester, fetus 1 (this code)
• O36.0922 Maternal care for other rhesus isoimmunization, second trimester, fetus 2
• O36.0923 Maternal care for other rhesus isoimmunization, second trimester, fetus 3
• O36.0924 Maternal care for other rhesus isoimmunization, second trimester, fetus 4
• O36.0925 Maternal care for other rhesus isoimmunization, second trimester, fetus 5
• O36.0929 Maternal care for other rhesus isoimmunization, second trimester, other fetus