Congenital Anomalies
Written by Rhiana Devadasan
20) Congenital anomalies - teratogenic factors and prenatal diagnosis.
21) Congenital diseases - basic principles of surgical treatment.
22) Congenital anomalies of head and neck.
23) Congenital anomalies of the gastrointestinal tract.
Dysmorphology = the branch of clinical genetics concerned with the study of structural defects, especially congenital malformations.
Congenital anomalies = structural or functional abnormalities (e.g. metabolic disorders) that occur during intrauterine life and can be identified prenatally, at birth or later in life. They can be isolated abnormalities or part of a syndrome. (aka Birth defects, Congenital disorders, Congenital malformations)
Result = physical, intellectual or developmental disabilities, ranging from mild to severe.
3 STAGES OF PRENATAL DEVELOPMENT:
- Preembryonic Period (aka implantation stage) - teratogens at this period will either kill the embryo or produce no harm if the embryo survives (i.e. all of nothing effect) from the time of fertilization to the end of the 2 weeks of gestation
- Embryonic stage - congenital anomalies normally develop during this stage from the beginning of week 3 to the end of week 8. 3 germ layers (endoderm, mesoderm, ectoderm) give rise to organ systems.
- Fetal stage - the fetus is less vulnerable to teratogenic effects, but the growth & development of organs such as the brain and eyes may still be affected from week 9 until birth.
CRITICAL PERIODS
3-6 weeks: CNS, heart, upper extremities, eyes, lower extremities
6-9 weeks: eyes, hands and legs, heart, palate, genitalia, ears
9-16 weeks: palate, genitalia, ears
20-36 weeks: lower sensitivity to tertogenic factors