ICD-10-CM > O00-O9A > O30-O48 > O36 > O36.0 > O36.09 > O36.091 O36.091 Maternal care for other rhesus isoimmunization, first trimester Non-Billable/Non-Specific Codes O36.0910..., not applicable or unspecifiedO36.0911..., fetus 1O36.0912..., fetus 2O36.0913..., fetus 3O36.0914..., fetus 4O36.0915..., fetus 5O36.0919..., other fetus