pregnant JRT found

Question
Essentially found:  was given around 2-3 y.o. male and female and the owner (an alcoholic who was losing her apt) didn't have shot records or anything.  So we first thought she was fat -- okay now we realize she's pregnant.  How do we know when we're close enough to start taking her rectal temps. I don't want to freak her out by checking for the next few wks.  So do we really need to have her xrayed.  I had a few litters 15 yrs ago without xrays.

Answer
Tami
Gestation is between 56 - 60 days, so if you can find out when she got pregnant you can start taking the temp about a week before she has the puppies. If there's no way to tell, you can check her vagina for a clear stringy discharge which is indicative of delivery within 24 hours. You shouldn't worry about freaking her out by taking her temperature, it doesn't hurt and is a good tool for you to be ready.
X-rays are smart to get because they let you know how many puppies she will be having and what to expect, as well as the size and possible delivery date of the puppies.
She needs good nutrition now and you should get updated on labor and delivery if it's been 15 years since you've whelped a litter, and then do everyone a favor and have the dogs spayed and neutered.
Very best of luck to all.