By the time you are 18 weeks pregnant, the baby's growth rate may have slowed down, but his or her reflexes are developing rapidly. Changes in your baby at about week 18 of pregnancy include increased fetal movements, the development of taste buds, and the hardening of the bones. When you're about 18 weeks pregnant, you may have an ultrasound to check the development of the baby; many pregnant women have an ultrasound between weeks 18 and 22 of pregnancy.