noun, noun which may take the genitive case particle 'no'
low body weight; underweight
Medical and general term for weighing less than the expected or healthy range. Often used in clinical contexts such as 低体重児 (low-birth-weight infant).
低体重で生まれた赤ちゃんは特別なケアが必要です。
Babies born with low body weight need special care.
彼女は低体重のため、医師から栄養指導を受けた。
Because she was underweight, she received nutritional guidance from her doctor.
やせ is a general term for thinness or being skinny, not necessarily implying a medical condition, whereas 低体重 specifically refers to low body weight.
Compound of 低 (てい, 'low') and 体重 (たいじゅう, 'body weight').