Our cats were terrified of the noise and hid in the spare room for about a week, in a state akin to shell shock. We put Feliway plug-ins upstairs and down and made sure that we devoted a small window of time every day for cat time - cuddling them, brushing them, playing with them. This helped them to adjust to not having as much attention as they were used to and we have never had any jealousy problems.
When the second baby arrived two years later they shrugged and carried on snoozing, as if to say 'oh yeah, one of those again. Hey ho'. The eldest is now a toddler and she adores the cats. Considering they had never laid eyes on a child two and a half years ago, they are amazingly tolerant of the shrieking and enthusiastic but rough handling.