This is the longest stage of prenatal, human development that lasts from 9 weeks after conception to birth. By the end of the 6th month, the fetus usually has developed internal organs (e.g., stomach and intestines), which also become functional. Many people believe that it is important to talk to the fetus to help foster attachment, and get the baby used to the sound of the parents voice. Others believe that this is not useful as the fetus can't hear. However, the reality is that the fetus is responsive to sound at approximately 6 months of development. So...talk it up, they can hear.