Thanks Amanda! Good answer!
That you are right on track. Your uterus grows in centimeters with your weeks. So at 30 weeks 5 days you are basically at 31 weeks and your uterus measured at 31 cm. So you are perfect. :) Any where within 2 weeks.. small or big... is considered normal. :) If you lean to much in one way your doctor will let you know they are concerned.