The length of the stats structure is the same as the number of blobs in your image.
[L, numberOfBlobs] = bwlabel(binaryImage);
stats = regionprops(L, 'All');
fprintf('There are %d blobs in the labeled image.\n', numberOfBlobs);
fprintf('There are structures, in the stats structure array.\n', length(stats));
You can see that length(stats) will be the same as numberOfBlobs.
