ICD-10-CM > O00-O9A > O30-O48 > O36 > O36.8 > O36.83 > O36.839 O36.839 Maternal care for abnormalities of the fetal heart rate or rhythm, unspecified trimester Non-Billable/Non-Specific Codes O36.8390..., not applicable or unspecifiedO36.8391..., fetus 1O36.8392..., fetus 2O36.8393..., fetus 3O36.8394..., fetus 4O36.8395..., fetus 5O36.8399..., other fetus