Why do i measure bigger one week and smaller the next?

Answer 1

In the early weeks of pregnancy fetal growth is fairly consistent and measurements are very accurate in a normal pregnancy. Differences would be most likely to more than one person interpreting the measurements from week to week.

After the half way mark at 20 weeks, the difference can be caused by the different people recording measurements, a baby who is small or large for dates, a baby whose growth pattern is not progressing "on average" or by restricted fetal growth - sometimes found in women with severe morning sickness (hyperemesis gravidarum).

If the differences are extreme and you are being measured by more than one person, request a recheck by the same healthcare provider several visits in a row.