- At about the eight week of pregnancy bone cells first appear. This is the signal that the developing baby is now a fetus. This also signals the start of the fetal stage of development. Starting at this time the baby will continue to grow to a length about 20 times the size he is at eight weeks. An ultrasound shows the size of the developing baby and is used to monitor the pregnancy.
- At the 12th week of gestation, the fetus starts to swallow and inhale amniotic fluid, the liquid that surrounds and protects the developing baby inside the womb. This stimulates the senses of taste and smell. It is also thought to help with the development of organs for respiration and digestion. At 14 weeks, the fetus will have mature taste cells. During weeks 11 to 15, the fetus' nose develops.
- At the 16th week, a fetus is able to listen to its surroundings. The baby will start to respond to the mother's voice and body. The ear and sense of sound is fully complete at 24 weeks. Even though the baby has many layers of protection she can still hear outside of the mother's body. Babies are able to remember specific sound patterns of music and speech. After they're born prefer the sounds they are familiar with from inside the womb.
- The developing fetus will not open his or her eyes until the 26th week of gestation. Even though the eyes may be closed the developing baby will be sensitive to light. When light is shown on a mother's abdomen, there is an increase in the fetus' heart rate. After birth, the eyesight will continue to develop. The newborn baby only sees 8 to 12 inches away with a visual acuity of 29/400; this progresses until it reaches 20/20 around 8 months of age.
- An ultrasound should be able to determine the gender of a fetus. Although the development is fairly similar, there can be a slight difference of behavior in the womb. It may seem to be an urban legend that baby boys will kick more, but male fetuses actually tend to be more active in the womb than female fetuses, according to "A Child's World: Infancy through Adolescence." Generally this will also continue during infancy.
