Nursing cat behaviour towards kittens

Question
Our young cat (12 months old) delivered a litter of 4 kittens 10 days ago. both she and the kittens appear well. however today she appears very restless, she is pacing around meiowing louldly looking wild eyed and frightened. She is also being rather rough with her kittens who have just opened their eyes and are starting to becone more mobile. could you tell me if this behaviour is normal as i am a bit concerned for the kittens saftey. she is letting them feed but every now and then appears to attack one of them, biting their legs, tails and tummy and pinning them to the ground. To be fair they are not crying out, but the mother cat seems aggressive in nature which is mosy unlike her. I would be very grateful for any advice.

Answer
This is not normal as mother cats are usually very calm with their babies.  I would recommend a trip to the vet.  There is a possibility that mom has a uterine infection (or some other medical problem) that is causing the odd behavior.  She certainly may be in heat again and hormones are causing the irritability.  She should be spayed to prevent further pregnancies and help curb the un-wanted behavior.