Once you’re 20 weeks pregnant, your doctor will place a tape measure from the top of your pubic bone to the top of your uterus to measure your fundal height (always in centimeters). The point of this measurement is to assess baby’s size, growth rate, and position. The measurement should also match your gestational period, give or take two centimeters. For example, if you’re at 20 weeks, your fundal height should be around 18 to 22 centimeters. As your belly grows, your fundal height should also increase. But there are many reasons why the measurement may be higher or lower than expected. Baby may be larger or smaller than average, baby may be in a breech or sideways position, or you could have gestational diabetes. If your doctor notices anything alarming about your fundal height, they’ll do an ultrasound to understand the cause. Though ultrasounds aren’t perfect, they’re more accurate than looking at fundal height alone.