The amount of amniotic fluid that surrounds and protects your baby is now at its maximum and the placenta has almost completed its growth.
Amniotic fluid is essential for your baby's lung development, gut maturation, protein requirements, and temperature control. Adequate fluid also allows your baby to move easily since she is in an almost weightless state. There is about 800 ml of amniotic fluid around your baby. The range, however, is quite wide and "normal" can be anywhere between 300 ml and 2 liters. Sometimes there is too little, a condition known as oligohydramnios, or too much fluid, a condition known as polyhydramnios, surrounding the baby. In this situation you would be closely monitored and premature delivery may be necessary.
It's not surprising that the size of your uterus may not reflect the size of your baby since there can be so much variation in the quantity of fluid.
As the amount of amniotic fluid reduces in late pregnancy, your baby is not as well cushioned and her movements may become more obvious, although you should bear in mind that increasingly, as she grows, she has less space in which to move around.