M.R.
Unless it were a significant amount of weight, I'd not bother with it at all. Besides, anytime you get weighed you can always consider that your true weight could fluctuate as much as 5 pounds heavier or lighter. Seeing as how you've lost 4 pounds, there are a lot of things that could explain it.
You would probably be a better judge as to when your baby is coming since you've already had 3 and know how your body has reacted in the past.