Sentence:  Her mother wrote Kate of her grief at the death of Kate 's <WSD>baby</WSD> and at Jonathan 's decision to go with the South `` And , dear Kate '' , she wrote , `` poor Dr. Breckenridge 's son Robert is now organizing a militia company to go South , to his good father 's sorrow . 
Meaning of the word marked with <WSD> tags:  a very young child (birth to 1 year) who has not yet begun to walk or talk