Starting at about 20 weeks, at each of your prenatal visits, your healthcare practitioner will measure your fundal height — the distance from your pubic bone to the top of your uterus. This measurement allows her to assess your baby's size, growth rate, and position. As a rule of thumb, your fundal height (in centimeters) should roughly equal the number of weeks you're pregnant. For example, at 20 weeks, your fundal height should be about 18 to 22 centimeters.
Did your doctor tell you you were TOO small? A measurment of 34 at 36 weeks would be on the small side of normal.
Measuring small for dates means your fundal height is more than 2 centimeters shorter than what's normal for your stage of pregnancy. Your practitioner will probably order an ultrasound to confirm your due date, in case you're not as far along as you thought, and to rule out problems such as intrauterine growth restriction and too little amniotic fluid.
Being small of stature or having well-conditioned abdominal muscles can give you a smaller initial fundal measurement. Or you may have a small, perfectly healthy baby. Some babies are small because their parents are small. But if your baby isn't growing as he should be, you'll have another ultrasound in a few weeks to check on his growth, and frequent monitoring to assess his well-being.


