Hmm, I'm sure bubs will just make as much room as he/she needs and soon you won't have much choice about it! But the thing I'd be considering is how the tightness of the jeans makes your whole pelvis feel, KWIM? Sometimes when we squeeze into jeans that are just a teeny bit too cosy-fitting (and I'm sure we've all done that, pg or not!) it compresses the joints at the back of your pelvis and will actually alter the way your hips move when you walk!

Actually, that doesn't really answer your question, sorry!