Just remember, when she brings the baby home, have someone else, not so close to the cats (say her bf or something?) carry the baby in and have her goo-goo over them. This way they won't feel left out and harmony will remain.
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One other suggestion - bring home a shirt or blanket worn by the baby. Put it on the floor where all the cats can get a whiff of it. Then they will be familiar with her/his smell from the beginning.