My bitch has had three puppies - a boy and two girls, and thanks to this site I knew what to expect.  The first baby came out but Pip didn't take the sac off, so I had to, and for a few minutes she didn't breathe.  The next, two hours later, was the same, but I took the sac off straight away and the little girl was breathing okay.  The last was a breech, and I panicked a bit, and had to pull the last puppy boy out the last bit.  There was no sac, but he was breathing fine.  Then I called the vet as the afterbirth was not present, and he reassured me that no attention was required, and sure enough it emerged an hour later.  All puppies thriving and getting fatter by the minute, and Pip is a natural.  My question is that I discovered Pip has fleas, and want to give her a 4fleas tablet.  I know you can give them to nursing mothers, but has anyone experience of this?

I would get something from your vet as they would know which was the safest product to use for a nursing bitch.

Congratulations  :D on the safe delivery of your new babies.
Good luck with them and make the most of them while they are tiny as they will be bouncing around in no time!
Regarding the fleas,has Pip been seen by a vet since delivery? If not I would recommend a visit just to have her and pups checked over and mention the fleas to him then. :)

As far as I know the only safe flea product is Frontline Spray (not the spot-on). It can be used when the pups are over 2 days old.

You can use Advantage on Mum at this stage which is avaliable from your vet. It is a "spot on" product.
The dander from Mum that falls onto the pups will also kill any fleas on the pups too.

My chihuahua had 5 pups 4 weeks ago, sadly one only made it to 2 weeks. This is my first time with pups. I do chihuahua rescue and when I got Neenya she was already expecting, anyway I was wondering if anyone could help me with somethings, !- what is good for them to teeth on they have a few teeth but I want them to learn to chew on certain things. and what is the right age to give to new owners some say 6 weeks others say 8 weeks 

Give them rib bones to gnaw; and most toy breeders keep the pups until about 12 weeks, as they're so tiny and fragile.