floppy infant; hypotonic infant
Medical term for an infant with abnormally low muscle tone, often associated with conditions such as Down syndrome or neuromuscular disorders.
A floppy infant often feels limp when held.
The doctor assessed muscle tone to diagnose the hypotonic infant.
筋緊張低下 is the general medical term for hypotonia (low muscle tone), while 低緊張乳児 specifically refers to an infant with this condition.
Compound of 低 (low) + 緊張 (tone/tension) + 乳児 (infant). A straightforward medical term with no obscure historical derivation.