Prenatal Development

Germinal Period

• conception - 2 weeks

  • classified as the moment when egg and sperm combine

  • creation of the zygote (fertilized egg)

  • cell division within 36 hours

  • cells are differentiated

  • inside cells —> embryo

  • outer layer of cells —> placenta, umbilical cord

Embryonic Period

• implantation - 2 months

• cell differentiation and organs appear

  • endoderm - inner - digestive & respiratory

  • mesoderm - middle - bones, muscles, circulatory and reproductive

  • ectoderm - outer - skin, sensory, nervous and brain

• development is cephalocaudal (head to foot) and proximodistal (near to far)

• placenta, umbilical cord and amniotic sac and fluid are developing.

Organogenesis - Organ Formation

• Week 3 - neural tube

• 21 days - eyes

• 24 days - heart cells differentiate

• Week 5-8 - arms and legs, face begins to form, intestinal tract, nervous system and brain

Fetal Period

• 2-9 months

• fetus begins to move

• fine details emerge

• genitals are identifiable

• fetus becomes viable around 24-25 weeks

Maternal Stress

• anxiety and stress can cause and increased risk of

  • premature birth

  • low birth weight

  • miscarriage

Prenatal Development Hazards

• teratogen - environmental agents that can harm the embryo or fetus

• effect depends on dose, genetic susceptibility, timing of exposure

Alcohol

• 5 in 1000 infants suffer from fetal alcohol syndrome

• symptoms: below average IQ, facial differences, defects in limbs and heart, deficits in perception, cognition, behavior

• outcome: shorter life expectancy

Smoking/Nicotine

• maternal smoking or exposure to 2nd hand smoke

• associated with: low birth weight, stillbirth and miscarriage, higher incidence of sudden infant death syndrome, longterm health, cognitive and behavioral issues, ADHD

Illegal Drugs

• cocaine

  • short term - low birth weight, smaller head circumference, poorer reflexes

  • long term - delays in motor functioning, attention difficulties, behavioral problems

• marijuana

  • short term - low birth weight, premature birth, increased chance of NICU

  • long term - lower IQ, depressive symptoms

• heroin

  • short term - withdrawal, tremors, disturbed sleep

  • long term - behavioral problems, attention difficulties

Paternal or Partner Factors

• exposure to lead, radiation, pesticides can affect health of sperm and increase risk of miscarriage

• older fathers associated with higher risk of miscarriage

• smoking

• partner support can lower stress in a pregnant person