Biting/scratching/hair pulling. Please help!

[Twogirls2]

Please help. My 18month has been scratching/biting/hair pulling for 6 months at nursery/at home/in public. Randomn attacks daily when she is happy playing she will lean over and bite or scratch, when she meets a new child, the same. She will lean over a scratch me when we are reading/cuddling. Got a baby due in 2 weeks! There doesn't seem to be any trigger despite all friends/family/nursery observing. Will she have behavior problems when she is older? We tell her no biting, tried time out for months, tried cuddling instead. Am list at what to do

It sounds like cause and effect. I bite , pull hair etc I get an amazing reaction - I think ill do it again.
They don't understand others feelings at that age.
You could do cause and effect back. Hour child bites something boring happens eg put in the corner and ignored. Don't ask then to say sorry at this age as they will not understand that.
Model behaviour eg take their hand and stroke your arm saying arrrrrr. Or do the same on another child.