We have just been through our third litter which does not make me an expert
Scans are rarely accurate. Pups can be hidden behind others or double counted. You also have another 20 days, or so, to go yet and lots can happen in that time.
Do you have a copy of The Book of the Bitch by JM Evans and Kay White. Its an excellent resource and gives guidance on feeding and exercise. You are right not to change your girls diet yet, exercise should be on lead walks now, ideally little or no running round.
I am sure there are others on here that can offer better advice and guidance but if she was my girl I would be getting her checked by the Vet, not least you may need their assistance at whelping and its a good way to stay connected with them.
This last litter weighed in at 1.4Kg (5 pups) and Mum was around 3Kg heavier at the time of whelping.
Good luck with your girl.
