“Issues in Prenatal Development”
For each of the 7 general causes of congenital anomalies, fill in the chart with definitions, types, descriptions and facts. Be sure
to define the terms in the shaded column headings
Genetic Disorders
Chromosomal Errors
Teratogens: Maternal Diseases – agents
Teratogens: Drugs
which cause damage to embryo or a fetus
Autosomal disorders – disorders caused by
recessive genes are PKU (causes developmental
delay) baby has difficulty digesting
phenylalanine; found in Caucasian babies
Sickle-cell disease – African infants – causes red
blood cell deformities; can’t carry enough oxygen
to tissues; few live to 20 years
Tay-Sachs disease – E. Jewish children; Fr.
Cdns.; severe intellectually delayed and blind;
live to 3 yrs
Trisomies – a condition where 3 copies of a specific autosome;
Viruses: may pass through the placental filters and
attack the embryo or fetus
Down Syndrome most common; 3 copies of chromosome 21; 1
in 800 children in Canada; intellectually delayed, distinctive
features, plus other health concerns
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Also Trisomy 13 and 18 – more severe; death by 1 year old
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Sex-chromosome Anomalies- associated with the sex
chromosomes;
Huntington’s – causes brain to deteriorate; risk 1
in 10 000; 50% chance if parent has it
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Sex-linked disorders – caused by recessive genes;
colour blindness; hemophelia (blood will not
clot); Fragile-X syndrome (developmental
delayed – males more often affected
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Most common is an XXY pattern
Called Klinefelter’s syndrome; 1-2 in every 1000
males
Intellectually delayed, at puberty experience
enlarged penis and breasts
Turner’s syndrome is single X patter; anatomically
female but show stunted growth and usually sterile
Imbalance in cognitive skills
1 in 1000 boys have extra Y chromosome – taller,
large teeth, normal puberty and intelligence
Rubella or german measles; can be deadly for
a fetus; may cause deafness, cateracts, heart
anomalies
Cytomegalovirus (CMV); herpes group;
transmitted thru bodily fluids
10% of infected newborns display serious
symptoms (deafness, damage to nervous
system, intellectual delay)
STD’s – sexually transmitted organisms that can be
passed frommotherto fetus
HIV: can cross the placenta andenter the fetus’s
bloodstream, or infant can contact the virus in the brith
canals during labour, or virus can be passed thru breast
milk; 3-4 per 10 000 births in Canada
Infants become ill within first 2 years; weakens immune
systems; children must restrict exposure to viruses and
bacteria
Others: syphilis, genital herpes, gonorrhea: cause variety
of anomalies
Prescription drugs: must be careful what you take
when pregnant; doctors recommend avoiding
drugs
Thalidomide in 1960’s – prescribed for morning
sickness; caused malformations of the limbs
Drugs for anxiety and depression have been
associated with increase risks of preterm delivery,
low birth weight, low Apgar score
Tobacco – smoker mothers are on average give
birth to babies of lower birth weight; also higher
rates of miscarriage, stillborn, premature babies,
neonatal death; even second-hand smoke provides
risks to baby
Alcohol – can adversely affect an ovum prior to
ovulation; mothers who drink heavily are at
significant risk to delivering FAS baby; smaller
brains, hear anomalies, hearing losses, faces with
distinctive features, smallish looking, wide-set
eyes; often have learning and behavioral
difficulties; SAFEST course is no alcohol at all
Psychotropic drugs – heroin, methadone can
cause miscarriage; babies addicts; Cocaine,
marijuana (mixed results; not implicated as a
human teratogen)
Teratogens: Others
Teratogens: Mutagenic, etc…..
Paternal Influences
Fetal Assessment & Treatment
Diet – some nutrients vital to prenatal
development;
Mutagenic (agents that cause changes to genomic DNA)
Father’s role – at least a portion of unknown causes of
malformations are related to paternal factors
Diagnostic tests
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Spina bifida: folic acid deficiency
during early stage pregnancy
Low birth weight – due to insufficient
calorie intake; connected also to
development of mental illnesses
adulthood
Greatest impact of malnutrition is on
the nervous system
Women should gain 11.5 to 16
kilograms during pregnancy
Age – trend in Canada – women having babies in
their 30’s; average age is now 29.3 years
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Most older moms have no
complications
Low birth weight is potential
Congenital anomalies (nervous
system, female genetalia anomalies,
cleft lip or club foot)
But teenage moms can have poor
prenatal care, unhealthy diets, smoke,
drink or do drugs…can be factors
Chronic illnesses – emotional or physical
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Severe depression can lead to slow
fetal growth and premature labour
Less likely to feel attached to their
fetuses
Heart disease, diabetes, lupus,
epilepsy can also affect prenatal
development
Hence: Fetal-maternal Medicine: helps
manage pregnancies of women with
such conditions listed above
Exposure to radiation, chemical toxins can cause
mutations that interfere with conception and
embryo/fetal development
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Environmental (agents can damage cells or disrupt or damage
cell development)
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Can cause such things as disruption of neural
networks in the brain
Epimutagenic (agents that cause abnormal gene silencing or
expression without changing DNA)
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Ex. Infertility, miscarriage, congenital
abnormalities
Higher percentage of risk with men working
in certain occupations (janitors, painters,
printers, firefighters, woodworkers)
Also agriculture, gardeners, butchers, the arts
Exposed to solvents, preservatives, pesticides,
hydrocarbons, etc.
2/3rds “unknown” factors
Eg. A mother’s diet can produce enduring changes
on successive generations - i.e. our diet may
impact our grandchildren
Sperm – may be toxins in the seminal fluids that can be
transmitted during intercourse
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DNA damage to sperm can contribute to
congenital anomalies
Also concern over impact of father’s age
Evidence links adverse birth outcomes with
both teenage fathers and older fathers
Physical abuse – abuse of mother during pregnancy
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Can lead to premature labour
Premature breaking away of the placenta
Low birth weight
6% of pregnant Canadian women affected
2/3rds perpetrated by husband, boyfriend, or
“ex”
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Preconception and first trimester
screening assay the potential for
developmental complications
Tests can identify chromosomal errors
for many disorders
o
chorionic villus sampling
(CVS):
Cells are extracted from the
placenta
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amniocentesis – done at 14-16
weeks; needle extracts amniotic
fluid ; can diagnose
chromosomal and genetic
disorders
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maternal blood, urine, and
amniotic fluid can help monitor
fetal development
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Fetoscopy – insertion of a tiny
camera into the womb to observe
development – can be used for
fetal blood transfusions and bone
marrow transplants
Maternal emotions: anxiety and depression lead
to changes in body chemistry
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May eat less, weakened immune
system – can retard fetal growth