Environmental Influences
on Birth Defects
Inadequate nutrition of mother
o Stunt Brain Development of Baby
o Lead to mental retardation
o Increased risk of multiple birth defects
Exposure to diseases or infections during
pregnancy
o Rubella, or German measles, during first
trimester of pregnancy
Can cause severe birth defects including:
Blindness
Deafness
Heart disease
Mental retardation
o Toxoplasmosis
Parasite causes blindness, hearing loss, and
learning disabilities, and death
Found in cat litter and some raw meats
o Varicella, or chicken pox, during first half of
pregnancy
Cause scarring of the baby’s skin, limb
defects, eye problems, and miscarriage
o Sexually transmitted diseases (STDs) can be
passed to unborn child and can lead to serious
illnesses, physical disabilities, or death
Harmful substances consumed during pregnancy
o Nicotine from smoking tobacco or secondhand
smoke
Smaller than average babies
Miscarriages and premature deliveries
Respiratory infections or allergies
Fetal Alcohol Syndrome (FAS)
o 20% of infants die
o Facial deformities
o Delayed physical growth
o heart defects
o Hyperactivity
o Mental retardation or disabilities
o Poor coordination
o Difficulty controlling behavior
Drugs, over-the-counter and illegal
o Even over-the-counter drugs can potentially
cause serious defects if taken during pregnancy
Nothing should be taken during pregnancy
without doctor’s permission
o Pass on drug addition to the baby
Makes it necessary for baby to go through
painful withdrawal period after birth
o Produces severe, long-term learning and
behavioral problems
o Large amounts of caffeine increase risk:
Miscarriage
Low birth-weight babies
Infant death
o Cocaine increases risks:
Miscarriage
Produces strokes that lead to:
Brain damage
Heart attack
Birth abnormalities
Death
Causes:
Tremors
Irritability
Sleep problems
Developmental delays
Exposure to hazards during pregnancy
o Chemicals
Some types of:
Paint
Pesticides
Lead-based chemicals
Carbon monoxide
Mercury
Solvents
Paint thinners
Formaldehyde
Potentially cause physical and mental
abnormalities in unborn baby
o X rays can cause:
Childhood cancer
Miscarriages
Mental retardation
o Toxoplasmosis
Extreme high blood pressure
Accidental injuries
o Cerebral palsy caused by damage to the brain
before, during, or shortly after birth
o Damage to the developing embryo and fetus
from accidental injuries of all types can
potentially cause a wide range of birth defects
Hereditary Influences on
Prenatal Development &
Birth Defects
Dominant genes are stronger; recessive are weaker
Defective recessive genes inherited from both
parents
o Cystic fibrosis
Caused by inheritance of recessive genes
More likely to affect Caucasians than
African- or Asian-Americas
o Tay-Sachs disease
Inherited disease most common among
eastern European families of Jewish
descent
o Sickle cell anemia
Malformed red blood cells that deprive the
body of oxygen and prevalent in African-
Americans
Defective dominant gene inherited from one
parent
o Hemophilia
Passed on from mothers to sons only
Prevents blood from clotting
o Huntington’s disease
Manifests in adulthood
Leads to dementia (loss of brain function, memory loss)
o Duchenne muscular dystrophy
Transmitted by female carriers
Usually affects only males
o Color blindness
Usually affects only males
Errors in chromosomes--Problems with the
number or structure of chromosomes
o Down syndrome
Associated with mental retardation
Increased risk of heart defects
Leukemia
Poor muscle tone
Distinctive physical characteristics
Hereditary &
Environmental Influences
on Prenatal Development
& Birth Defects
Heart Defect
o Inherited
o Drug use
o Virus during pregnancy
Cleft lip/cleft palate
o Gap in upper lip or palate
Spina bifida and hydrocephalus
o Risk can be reduced by taking folic acid
during pregnancy
Multiple births
o Hyper-ovulation gene may be inherited from
the mother--Leading to fraternal twins
o Primarily influenced by environment
Twin-to-twin syndrome (TTTS) is the
result of one twin taking nourishment
from the other; fertility drugs