Answer by  
                                                                                          Justbarb (98)
                                                            
                          
                          
                                                          Not long and you won't know it when it happens because you'll probably be asleep. Unlike dogs, cats demand privacy for birthing. Chances are she's already picked a secluded place (not the box you prepared), and you'll only become aware of the event by the kittens' mewing. If disturbed, she will move the litter to another secluded place.