I have an 8 1/2 month old pure bread Boston Terrier who just went thru her first heat. I have a 6 year old male which we thought we did well on separating the two during this time. Now my female's teats seem a little larger and I am afraid that she may be pregnant. How can I tell and what are the dangers of this?

OOPS.........I would take her to the Vet to have her checked. It is very young for her to be having pups. She isn't mature yet and there could be problems with the pups and the Mom, especially during the delivery. A Vet check is strongly advised.
Good Luck

How long ago was she in heat? Dogs are a funny lot, I have one that goes into heat and when she doesn't get pregnant produces milk anyway because she knows she should be pregnant or about to give birth at least. It could just be a phantom preg.

Unless your vet does some expensive tests there is no way to verify there are puppies. I went with the morning after shot. I did that 'just in case' with my lola and she hasn't grown a lick since! The shot did her no favours and we weren't 'sure' she was preg either.

just a something more to consider
Hope it helps
Amy