How to tell gravid

I came across a rattlesnake on the road a couple of weeks ago while road herping, I was curious to find out if you can easily tell if the rattlesnake is gravid, the tail seems smaller and very plump above where the spurs would be.

Without doing an ultrasound it is a guess. If you have seen enough of them you can sometimes tell when you come across gravid females. Are you sure it was a female to start? They should be giving birth here over the next month or two. What did you do with the snake, and what species is it? Rattlesnakes are good about flattening themselve out when approached to make them look bigger in size. This behavior can fool you into thinking it is gravid.

Yes, it was flat on the road. I simply took some photos and kinda "shooshed" it away from the road, I've seen enough snakes ran over already.

Anyway, I will try and upload these photos I took at a later time. Thanks.