Stages of Prenatal Development

Prenatal development unfolds in three key stages: germinal, embryonic, and fetal. Each stage plays a vital role in forming the foundation for a healthy baby, highlighting the importance of early development in understanding human growth and behavior in PSYC 210.

1. Germinal stage

   • Lasts from conception to about two weeks.
   • Involves the formation of a zygote and initial cell division.
   • The zygote travels down the fallopian tube toward the uterus.
   • Key processes include cleavage and the formation of a blastocyst.

2. Embryonic stage

   • Occurs from the third to the eighth week of pregnancy.
   • Major organs and structures begin to develop, including the heart and brain.
   • The embryo is highly sensitive to environmental influences, such as teratogens.
   • This stage is crucial for establishing the foundation of the body plan.

3. Fetal stage

   • Lasts from the ninth week until birth.
   • Characterized by rapid growth and maturation of organs and systems.
   • The fetus begins to exhibit movements and responses to stimuli.
   • Development of fat layers and preparation for birth occur during this stage.

4. Zygote formation

   • The zygote is formed when a sperm fertilizes an egg.
   • Contains genetic material from both parents, establishing the genetic blueprint.
   • Undergoes mitotic divisions to become a multicellular organism.
   • Marks the beginning of prenatal development.

5. Implantation

   • Occurs around 6-10 days after fertilization.
   • The blastocyst attaches to the uterine lining, initiating pregnancy.
   • Essential for establishing a connection between the mother and developing embryo.
   • Successful implantation is critical for further development.

6. Gastrulation

   • Takes place during the third week of development.
   • Involves the formation of three germ layers: ectoderm, mesoderm, and endoderm.
   • These layers give rise to all body tissues and organs.
   • Sets the stage for complex body organization and structure.

7. Neurulation

   • Occurs shortly after gastrulation, around the fourth week.
   • The neural tube forms, which will develop into the central nervous system.
   • Critical for brain and spinal cord development.
   • Defects in this process can lead to serious conditions like spina bifida.

8. Organogenesis

   • Takes place from weeks 3 to 8 of embryonic development.
   • Involves the formation of major organs and systems from the three germ layers.
   • Each organ system begins to take shape and function.
   • This stage is vital for the embryo's viability and health.

9. Quickening

   • Refers to the first noticeable movements of the fetus, typically around 16-25 weeks.
   • Marks a significant milestone in fetal development and maternal awareness.
   • Indicates the development of the nervous system and muscle control.
   • Provides emotional bonding opportunities for the mother.

10. Viability

    • Refers to the ability of the fetus to survive outside the womb, typically around 24 weeks.
    • Advances in medical technology have improved survival rates for preterm infants.
    • Factors influencing viability include gestational age and health conditions.
    • Understanding viability is crucial for prenatal care and ethical considerations in developmental psychology.