Multithreading on window constructors

[nagendrababu]

Hi All,
I am developing an Widgetapp, Which has MainMenuWindow(480*800 pix) with QStackedwidget(480*500 pix) in it. I have added all my other windows(around 10 each with multiple widget's inside them) to stacked widget. The reason for this approach being, The top and bottom menu options are common across all windows, which I added to MainMenuWindow, based on Menu selected I am changing stacked widget index to show the corresponding window.
But the problem with this approach is, On bootup of the system, I am calling MainMenuWindow constructor which calls all other window constructors inside it. But all this process taking up around 1-2 Minutes, Which is causing my app fall outside acceptable bootup delay range of 15-30 secs.
I am thinking of initializing threads for each window constructor to run them in parallel, and wait for all threads to finish after constructor is done. But not sure how feasible this solution would be.
Any help in this prospect of how to do this in a graceful way or any better idea to solve this unwanted delay?

Thanks,
Nagendra.