Prenatal Development

Question 1

Prenatal Period

Answer 1

• Conception-Birth (38 weeks)
• Three stages: Germinal, Embryonic & Fetal
• Begins with creation of a zygote
• Single-celled organism formed by the union of sperm and ovum
  All other cells develop from zygote

Question 2

Germinal Stage

Answer 2

• 2 weeks after conception
• Within 36 hours of fertilization, cell division starts and zygote becomes increasingly multi-cellular
• Zygote moves down fallopian tube into uterus
• Attempted implantation at 7 days
• Process takes 7 days
  1/5 pregnancies end at this point with rejection of zygote

Question 3

Embryonic stage

Answer 3

• From 2 weeks (after implantation) until end of second month
• Vital organs and bodily systems start to grow
• Period of major vulnerability
• Most miscarriages occur in this window
  Most major structural problems arise

Question 4

Fetal stage

Answer 4

• From 2 months until birth
• Muscle and bones form, allowing physical movement
• Final three months brings intense brain development
• Age of viability: Fetus can survive premature birth (22-26 weeks)
  Survival rate jumps to 85% at 26-28 weeks

Question 5

Environmental Factors

Answer 5

• Fetus is not immune to environmental factors

Development can be affected by mother’s eating habits, drug use, physical health

Question 6

Nutrition

Answer 6

• Fetus needs a variety of nutrients
• Risk of birth complications and neurological defects with maternal malnutrition
• Prenatal malnutrition has been linked to increased risk of developing schizophrenia and other psychiatric disorders
• Low birth weight is associated with increased risk of heart disease and diabetes in mid-life
  That said: Hard to dissociate common co-morbid factors (drug use, poor health care)

Question 7

Drugs

Answer 7

• Teratogens: Non-genetic agents that can cause malformation of the embryo and/or fetus
• Primarily refers to drugs, maternal illness and environmental toxins
• May include malnutrition
• Most drugs past through placenta
• Includes prescribed drugs
• Most women only told to take Tylenol during pregnancy
• Thalidomide (wonder drug for insomnia, coughs, colds and headaches)
• Initiated study of teratogens
• Mild sedative and painkiller
• Produced birth defects that varied according to when mother took drug
• Malformation of eyes, ears
• Deformation of internal organs
• Fused fingers, toes
• Phocomelia: Limbs are shortened, hands and feet are connected to torso like flappers
• Virtually all recreational drugs can be harmful
• Heroin: Born addicted to narcotics, further risk of birth defects and respirator difficulties
• Cocaine: Reduces blood flow, limiting oxygen and nutrients; difficulty. Regulating alertness; abnormal sleep patters
• Marijuana: deficits of executive function (attention/impulsivity, problem solving)
• Caffeine: Most commonly consumed when pregnant
• Associated with miscarriage, prematurity, low birth weight, irritability, poorer muscular development and reflexes
• Heavy drinking can lead to Fetal Alcohol Syndrome
• Microcephaly; heart defects; delayed mental and motor development; cranio-facial malformation
• Most commonly known cause of intellectual disability
• Nicotine: Estimated 10.5% of pregnant women smoke
• Reduces blood flow and nutrients
• Constricts blood vessels/suppresses appetite
• Babies are smaller
• Change of prematurity and complications increases with # of cigs smoked/day
  Increases risk of SIDS (sudden infant death syndrome)

Question 8

Infection

Answer 8

• Placenta prevents most infections from passing, but not all
• Rubella, mumps, severe flu can be dangerous
• Syphilis: CNS damage, deformities of teeth and skeleton, death
• Gonorrhea: Premature birth, blindness (if untreated) Silver nitrate drops at birth
• Link between maternal infection (influenza, rubella) in first half of pregnancy and SZ
• Virus directly affects fetal brain
• Body’s inflammatory response (IL-8)
• Fever from cytokines
• Auto-immune response
• Most are preventable with early & consistent medical care
  Health Canada recommends exclusive breast feeding until 6 months

Question 9

Toxins

Answer 9

• Mercury: between 1954-1960, industrial dumping of Hg in a bay in Japan
• Caused cerebral-palsy disorder (neurological)
• Lead: Linked to miscarriage, neuromuscular problems, ID
• BPA: Girls are more aggressive, hyperactive (no affect in boys)
  Disrupts estrogen in developing brain