Jobs' 4th child on the way

"His wife is expecting," said Lou Mazzucchelli, a Gerard Klauer Mattison & Co analyst. "He has been saying that family comes first and he is demonstrating it here."

An Apple (Nasdaq:AAPL) spokeswoman said Jobs had a "previous West Coast commitment" and would not comment on Jobs' wife.

Apple has said that Phil Schiller, the company's vice president for worldwide marketing, will step in as the main speaker at Macworld, with Jobs scheduled to participate via teleconference in the 9 a.m. ET keynote Wednesday. It is unlike Jobs to miss Macworld, the biggest show for Apple product developers and users, which takes place twice a year in the U.S. This is the first time the summer show will take place in New York, after being in Boston for many years. The switch was made to focus on the creative and publishing community in New York, one of Apple's core customer groups.

This year's Macworld is one month from the first anniversary of the surprise announcement last year of Microsoft Corp.'s investment of $150 million in its former arch-rival and the revamping of Apple's board of directors, including the appointment of co-founder Jobs as a director.

"(News) probably won't be at that level, like last August," said an Apple spokeswoman. "But you never know."

Reuters contributed to this report.