That depends on when you had her mated. The stud dog owner should be able to tell you, but you would not normally be able to see anything for at least three weeks.
First signs are slight thickening of the waistline, nipples getting pink and hard and generally she will be a bit more lovey dovey and wanting cuddles.
After about six weeks you will be able to see much easier.
You can have them scanned (ultrasound), again after about 3 weeks, and you can have them xrayed but do not do this until at least 8 weeks as the bones are not calcified until then and the radiation could harm them.