。
Her baby is due this month.
Literal
She [topic-は] this-month baby [subject-が] is-born [scheduled-予定] is.
The double-marking 彼女は…赤ちゃんが is a hallmark of Japanese topic-comment structure: 彼女は frames the topic ('about her'), and 赤ちゃんが marks the actual subject of the embedded predicate (生まれる). English has to recast this as 'her baby' with possession, while Japanese keeps the relationship implicit. This XはYが pattern surfaces constantly with body parts (彼は背が高い 'he is tall'), abilities (私はピアノが弾ける 'I can play piano'), and situations like this one. ~予定 marks the timing as scheduled rather than definite.