Explain Fetal Development?

The medical profession divides pregnancy into three-month stages called trimesters. At the end of the first trimester, the fetus is only about 5 cm long. During the second trimester, the head remains large, but not markedly so in comparison to the rest of the body, Major organs are mostly complete, blood cells develop, head and body hair appear, and movement may be felt by the mother. The fetus may begin sucking its thumb, and begin cycles of waking and sleeping.

During the final trimester, from sixth to the ninth month, the fetus is normally viable, if born. The major organs have completed development, although they are not used until after birth. The head is so large that it must usually be slightly compressed to pass through the birth canal. The fetus usually can survive outside the womb beyond the age of 7 months. It reacts to music and loud sounds, and may even recognize its mother's voice.