How accurate are ultrasound weight measurements?

Jamisha β€’ πŸ‘­πŸ’ΈπŸ₯‚πŸ’Ž

I had an ultrasound done yesterday and the Tech said my baby was weighing "around 5Ibs" . Before my ultrasound my Dr. said baby was measuring little but not to small.. im hoping she won't be to big or too small. Due to me being high risk pregnancy there hoping I deliver around 37-39 weeks if not I'll be induced before 40weeks...I still have a few more weeks to go. How are techs even able to estimate how much the baby weighs? Has anyone ever had there baby weigh close to what was estimated for baby's weight?