CHAPTER 3CONCEPTION, PRENATAL DEVELOPMENT, AND BIRTH
In this chapter
• What happens during the first nine months of development?
• Will the baby be normal?• What should parents do during pregnancy to
optimize the baby’s health?• What happens during the birth process?
Conception and the Zygote: The First Two Weeks
• Gestation – period from conception to birth• Within hours of conception, the sperm and egg
create a zygote.– End of first week differentiation of cells begins.– During second week implantation occurs.
• Infertility– Primary factors affecting infertility include health, lifestyle,
and age,– Treatments: fertility drugs, artificial insemination, IVF,
surrogate mother
Figure 3.1: Changes between 1970 & 2005 in Age When Women Have Their First Child
The Embryo: Weeks Three Through Eight
• Specialized layers of cells– Ectoderm– Mesoderm– Endoderm
• Organs begin to function– “Primitive streak”– Neurogenesis
The Fetus: Week Eight to Birth
• Size of fetus increases twentyfold• The brain and behavior– Some neurons die off as others make new connections.– CNS becomes active and responsive in mid-pregnancy.– Prenatal behavior shapes further brain development.
• Learning– Fetuses recognize repeated, familiar sounds.
• Individual differences– Differences in heart rate, activity level
Boy or Girl?
• Prenatal development– Stage 1 – male and female have similar gonadal streak,
Müllerianducts, and Wolffian ducts– Stage 2 – physiological sex differences emerge– Stage 3 – external genitals form; testosterone stimulates
development of testicles and penis– Stage 4 – testosterone inhibits the cycles of the
hypothalamus and pituitary, which regulate female ovulation
Prenatal Development
• Ultrasound imaging• Chromosomal malformations– Caused by mutations or accidents during meiosis– Down Syndrome
• Recessive genes– Most genetic disorders carried on a recessive gene– Sickle cell– Hemophilia
• The Founder Effect
Genetic Counseling
• Beneficial when– member of group know to be at risk– Experienced miscarriage, stillbirth, or infertility– Woman is over 35
• Karyotype• Prenatal testing– Preimplantation genetic diagnosis– Amniocentesis– Chorionic villi sampling
Video: Prenatal Assessment
Protecting the Fetus
• Maternal characteristics– Age– Diet and nutrition– Stress
Protecting the Fetus
• Outside influences– Teratogens– Diseases– Medications– Drinking and smoking
• Alcohol• Nicotine
– Illicit drugs• Heroin• Cocaine
– Environmental toxins
Figure 3.3: Sensitive Periods in Prenatal Development
Pregnancy and Parents-to-Be
• Experience of pregnancy depends on timing
• Women’s concerns over course of pregnancy
• Social and emotional challenges of pregnancy
Video: Effects of Drugs on Learning
Birth
• Labor and delivery– Mother’s pituitary gland releases oxytocin, which triggers
uterine contractions.– Labor consists of involuntary contractions.• Stage 1 – cervix opens to 4 centimeters• Stage 2 – baby’s head, then body, pushed into birth
canal• Stage 3 – contractions expel placenta
Birth Complications and Controversies
• Complications– Anoxia– Cesarean section
• Newborns at risk– Preterm– Low birth weight– Respiratory distress syndrome
Infant Assessment
• APGAR– Appearance– Pulse– Grimace– Activity– Respiration
• Neonatal Behavior Assessment Scale (NBAS)
Video: Birth and APGAR Assessment