Introduction to Psychology/Child and Adolescent Psychology/Prenatal Environment

Prenatal development is the development of an organism before its birth.

Stages of Prenatal Development

1. Germinal stage – conception to 2 weeks
   • Begins at conception and ends when the zygote implants itself in the mother's uterine lining.
   • Between 8 and 12 days after conception, implantation occurs. This is when the zygote embeds itself in the inner lining of the mother's uterus.
2. Embryonic stage – 3 to 8 weeks after conception
   • blastocyst differentiates to form three cell layers in the embryo: the ectoderm, mesoderm, and endoderm.
     • The ectoderm is the outer layer of the cell mall, and during the embryonic stage it gives rise to the nervous system, sensory receptors, and outer skin layers.
     • The mesoderm becomes the circulatory system, skeleton, muscles, excretory system, reproductive system, the outer layer of the digestive tract, and the inner layer of the skin.
     • The endoderm will eventually become the respiratory system and the remainder of the digestive system.
   • chronological development following conception
     • 3rd week - vulnerable brain cells and spinal cord form from the neural tube
     • 3rd and 4th week - placenta and umbilical cord form
     • by 4 weeks - eyes begin to form, torso continues to form, heart tissue begins to beat, arm buds appear
     • by 5 weeks - arms are developed and legs buds begin to form
     • during 8th week - organogenesis is complete, signaling the end of the embryonic stage and beginning of the fetal stage
3. Fetal stage - week 9 to birth (38–40 weeks)
   • chronological development following conception
     • 9 through 12 weeks - first arm and leg movements begin, reflexes appear, sex organs develop.
     • 17 through 20 weeks - mother begins to feel movement, heartbeat can be heard with a stethoscope.
     • by 24 weeks - fat forms and rapid weight gain begins
     • 26 through 28 weeks - lungs are mature enough to allow breathing
     • 28 though 40 weeks - major organ systems are functional and brain develops rapidly.

Teratogens

• preterm births occur before 37 weeks of gestation
• low birth weight is less than five and half pounds (two pounds lighter than average)

• Fetal Alcohol Syndrom (FAS)
  • overall growth deficiency, head and facial malformations, and dysfunction of the central nervous system
• effects of alcohol use
• effects of cocaine use
• effects of cigarette smoking
• sexually transmitted diseases
• effects of stress