Congenital Malformations + Teratology Flashcards
What are malformation abnormalities and what causes them?
- Occur during formation of structures
- Most originate 3-8th week of gestation
causes = environmental/genetic factors
What are disruption abnormalities?
- Alteration of pre-existing structures due to destructive processes
e. g. amniotic band syndrome/ limb amputations
What are deformation abnormalities?
- Mechanical factors which mould fatal parts over prolonged periods
e. g. clubfeet = from compression in amniotic cavity
What is Oligohydraminos?
- Type of sequence abnormality
- Deficiency of amniotic fluid
What are syndromes?
- Pattern of malformations occurring together, considered to have specific common cause
- Term indicates diagnosis made + risk of recurrence known
What are associated recognised patterns of malformation?
Where initiating cause has not been identified
What is teratology?
The study of abnormal development (prenatal)
What are teratogens?
Anything capable of disrupting embryonic or fatal development + producing malformations/birth defects
What are the 3 pain principles of teratogenesis?
- Dosage
- Time + length of exposure
- Genotype of embryo
What causes birth defects?
- Chromosomal abnormalities
- Single gene defects
- Enviro
- Multifactorial
- Unidentified
What are the types of chromosomal abnormalities?
Numerical or Structural
What percentage of conceptions end in spontaneous abortion?
50% -> 50% of these = due to chromosomal abnormalities
What are the most common chromosomal abnormalities?
- Monosomy (Turner syndrome)
- Triploidy
- Trisomy (21, 18, 13)
What causes chromosomal abnormalities?
Chromosome breakage =
- loss of broken piece
e. g. Cri dut Chat dyndrome - microdeletions
- fragile sites (regions of CGG repeats)
e. g. Fragile X syndrome
What is Cri dat Chat syndrome?
- Partial depletion of short arm of chromosome 5
- Children have catlike cry, microcephaly, mental retardation + congenital heart disease
What is Fragile X syndrome?
Mental retardation, large ears, prominent jaw
What is the risk of Rubella during pregnancy?
Preconception - minimal risk
0-12 weeks
- 100% risk congenital infection
- major abnormalities
- risk spontaneous abortion
13-16 weeks - deafness + retinopathy
After 16 weeks - normal development, slight risk deafness + retinopathy
What are the risks of pregnant women being exposed to radiation?
Babies with microcephaly, skull defects, spina bifida, blindness, cleft palate + limb defects
No known max. safe dose
Indirect effect of radiation on germ line cells = congenital malformations successive generations
When is the greatest risk of congenital malformations from drug use during pregnancy?
1st trimester - 3rd-11th week of pregnancy
What affect do drugs have during the 2nd-3rd trimester?
- May affect fetal growth/development or toxic effects of fatal tissue
- Drugs given shortly before term/during labour may adversely affect labour or neonate after delivery
What were the consequences of Thalidomide use during pregnancies?
- Increased frequency of phocomelia - babies born with segments of limbs missing
- Drug given to prevent morning sickness
- Critical period for limb formation
What are the contraindications and warnings during pregnancy?
- Accutane
- v. high risk severe birth defects
- inc. facial abnormalities, eyes, ears, skull, CNS, CVD + other
- increased risk spontaneous abortion/premature births reported - Industrial agents
- lead, mercury, pesticides - Recreational
- alcohol, tobacco, cocaine - Hypothermia
What are the effects of tobacco on pregnancy?
- Doubles rate of premature delivery
- Reduces birth weight = leading predictor of infant mortality
- Nicotine constricts blood vessels of placenta = reduces blood flow to infant
- Nicotine crosses placental BB + affects brain development + impairs cell growth
- IUGR = intrauterine growth restriction
