Title: Prenatal Development | Introduction to Psychology
Headings: Prenatal Development
Prenatal Development
Learning Objectives
Prenatal Development
Germinal Stage (Weeks 1–2)
Embryonic Stage (Weeks 3–8)
Fetal Stage (Weeks 9–40)
Prenatal Influences
What Do You Think? Should Women Who Use Drugs During Pregnancy Be Arrested and Jailed?
Infancy
Link to Learning
Think It Over
Glossary

Content: Fetal Stage (Weeks 9–40)
When the organism is about nine weeks old, the embryo is called a fetus. At this stage, the fetus is about the size of a kidney bean and begins to take on the recognizable form of a human being as the “tail” begins to disappear. From 9–12 weeks, the sex organs begin to differentiate. At about 16 weeks, the fetus is approximately 4.5 inches long. Fingers and toes are fully developed, and fingerprints are visible. By the time the fetus reaches the sixth month of development (24 weeks), it weighs up to 1.4 pounds. Hearing has developed, so the fetus can respond to sounds. The internal organs, such as the lungs, heart, stomach, and intestines, have formed enough that a fetus born prematurely at this point has a chance to survive outside of the mother’s womb. Throughout the fetal stage the brain continues to grow and develop, nearly doubling in size from weeks 16 to 28. Around 36 weeks, the fetus is almost ready for birth.