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