One sign that a cat is almost ready to give birth is that she will exhibit nesting behavior--she will restlessly seek a place to deliver her kittens. It is important to provide your cat with a birthing box large enough to accommodate her and her kittens during and after birth.
Size
Generally, a box that is 2 feet long, 1 ½ feet wide and 1 foot high, will suffice as a birthing box. The ultimate goal is to make a box that is large enough for your cat to stretch out and change positions in, yet small enough for her to feel cozy and secure in.
Function
The purpose of a birthing box is to ensure that your cat and her kittens are warm and safe, according to Felineexpress.com.
Types
Common birthing boxes include laundry baskets, wooden crates and cardboard boxes.
Time Frame
You should introduce your cat to her birthing box two weeks prior to her expected delivery date. This will give you enough time to observe your cat's visits to the box and determine whether or not she is comfortable with where you have placed it.
Warning
If you use a laundry basket as a birthing box, make sure that the side openings are extremely thin and small so that the kittens will not get their heads stuck in them.