It will destroy your relationship with the cat and it could lead to a serious aggression problem. Place the cat beside you while you pet it, not in your lap, and give Kitty a treat. Repeat the procedure. Pet and pay attention to the cat only when the cat is beside you, not on top of you. Cats are very sensitive to their environment.
Some cats stress easier than others.
To minimize the stress the cat may feel, it is best to prepare the home in advance of the new arrival. The earlier, the better . When you set up the nursery, let the cat explore and investigate the new furniture and equipment. At the same time train the cat to avoid the surfaces to be used by the baby. Place it on the surfaces you want the cat to avoid such as the bassinet and crib mattress, the top of the changing table, the playpen, and the carriage.