teratogenesis: birth defects, prenatal diagnosis, prevention Flashcards
1
Q
teratology
A
- teratogens: factors that cause birth defects
- dysmorphologists: clinicians studying, diagnosing and treating children with birth defects: usually pediatric geneticists
- ancient discipline
- critical periods vary depending on the apparatus
2
Q
critical periods in human prenatal development: blastocyst
A
- many zygotes, morulae, blastocysts abort spontaneously
- implantation of the blastocyst may fail to occur owing to inadequate production of progesterone and estrogen by the corpus luteum
3
Q
late period
A
- delayed by several days and unusually profuse: likely spontaneous abortions
4
Q
critical periods in human prenatal development: implantation
A
- overall early spontaneous abortion rate is approx. 45%
- fourth before pregnancy detected
- over 50% is from chromosomal abnormalities
- some chromosomal abnormalities are compatible with birth: congenital anomalies and syndromes
5
Q
early in gestation
A
- most structural defects are caused in 3-8 weeks when organ systems are forming
- before women realise pregnancy
- prevention of birth defects must begin before conception
- first prenatal visit at 8 weeks (10 weeks after LNMP): prenatal care has not resulted in significant defect reduction
6
Q
birth defects
A
- 2-3% diagnosed at birth
- 2-3% first years of life
- congenital doesn’t mean evident at birth
- 4-6% in total
- emotional and financial toll: high divorce rates
- leading cause of infant mortality (+ prematurity=50%)
7
Q
mechanisms of birth defects
A
morphogenetic processes depend on…
- cell size growth/control
- cell number control
- cell position
- cell adhesion/mobility
- genetic mutations, environmental insults may perturb these processes - dymorphogenesis - structural birth defects
8
Q
malformations
A
defective organ formation (organogenesis w3-8)
9
Q
disruptions
A
- alterations in already formed structures (vascular accidents, amniotic bands)
- amniotic bands: entrapment of fetal parts (usually limbs or digits) in ibrous amniotic bands while in utero
10
Q
deformations
A
mechanical forces alter structure (clubfoot, potter’s face)
11
Q
minor malformations
A
- can be indicators that other defects are present
- microtia: small ears
- birthmark: pigmented area
- 15% of all babies have 1 minor malformation
- one = 3% of major defect
- two = 10%
- 3+ = 20%
12
Q
causes of birth defects
A
- 15% genetic
- 10% environmental
- 20% multifactorial
- 50-60% unknown
13
Q
chromosome abnormalities
A
- trisomy 18 (Edwards syndrome)
- trisomy 21 (downs syndrome)
- turner syndrome: 45X
14
Q
thalidomide-induced defects
A
- late 1950s as antinauseant in early pregnancy
- critical teratogenic period for limb development
- heart defects
- proved that drugs can cross the placenta: babies are sensitive to what mother is exposed to
- limb defects: phocomelia
15
Q
environmental causes
A
- alcohol
- retinoids
- thalidomide
- antiepileptic drugs
- endocrine disruptors
- radiation
- infections
- maternal diabetes
- obesity
- nutritional deficiencies
