Can dogs detect pregnancy before you can?

So I volunteer at an animal shelter every Friday and Monday. On Friday, A beautiful lab mix momma just had puppies, who are in foster care. She doesn’t let anybody come near her and seems real agitated. Well, I took her into the patio pen to play with her and immediately she started loving on me. Anytime someone would come near me, she’d bark and growl at them and back her butt into me trying to protect me. I took a pregnancy test on Sunday and it turns out I’m pregnant! Is this just a coincidence? Or can dogs detect that kind of stuff before you can??