Some Does (female rabbits) just arnt cut out to be mothers and sometimes they will eat them, not feed them, or accidentally smother them. Those things can also happen if you touch the kits (baby rabbits) - most does will reject their kits if they have been handle by human hands, just like most other animals. For example - if a kit falls or accidentally gets kicked out of the nest box put rubber gloves on before picking it up and returning to the box.
Does need to be provided with a nest box - basically a regualar wooden box, the top is only covered halfway (its a place for the mother to be able to rest away from the kits when they are old enough to start roaming away from the box), and the front board is shorter in heighth for easier access.
Plenty of straw or haw needs to be provided for the mother to builder her nest inside the box, she'll had her own hair that she pulls from her tummy to the mix as well.
I feed my pregnant rabbits 16% protein rabbit food instead of the standard 8%. The 16 is used for meat rabbits, rabbits that suffer from weight loss, and I like to give it to my brood Does because the extra protein is good for them.
It is best that the cage that the babies are born in and stay in until weined have baby wire around the bottom sides of the cage or at least a board so that the kits don't fall out through the standard rabbit wire.
---Just an note before you decide to breed ---
I am a firm believer that animals should be bred only to improve future generations - weather its for better personality characteristics, conformation, color, size, etc. I just think that before you breed your rabbits you need to make sure that you are bring desirable kits into the world. Know what you are doing before you breed. Don't let it be a guessing game - running test after test.