ICD-10-CM > O00-O9A > O30-O48 > O36 > O36.2 > O36.21 O36.21 Maternal care for hydrops fetalis, first trimester Non-Billable/Non-Specific Codes O36.21X0..., not applicable or unspecifiedO36.21X1..., fetus 1O36.21X2..., fetus 2O36.21X3..., fetus 3O36.21X4..., fetus 4O36.21X5..., fetus 5O36.21X9..., other fetus