CONGENITAL ANOMALIES -Birth defects(Introductory note)

 

Simple Defination -It is a structural abnormality of any type that is present at birth. Etiology - Congenital anomalies may be induced by: 1.Genetic factors 2 Environmental factors Most common congenital anomalies, however, show the family patterns expected of multifactorial inheritance (determined by a combination of genetic and environmental factors). PREVALENCE-  About 3% of all live born infants have an obvious major anomaly. The incidence is about 6% in 2-year-olds and 8% in 5-year-olds. Congenital anomalies may be single or multiple and of minor or major clinical significance. Causes of congenital anomalies 1-Genetic factors such as chromosomal abnormalities and mutant genes. 2-Environmental factors e.g.: the mother had German measles in early pregnancy will cause abnormality in the embryo. 3-Combined genetic and environmental factors (mutlifactorials factors). Types of abnormalities 1-Malformations: this occurs during the formation of the structures of the organ (during organogenesis) results in partial or complete non formation or alterations in the normal structure. This occurs in the 3 to the 8 week of gestation. Ex. Cleft lip and or cleft palate. 2-Disruptions: results in morphological change of the already formed structure due to exposure to destructive process. e.g.: vascular accidents leading to intestinal atresia, amniotic band disruption. 3-Deformations: due to mechanical forces that affect a part of the fetus over a long period. Ex: talipes equinovarus deformity. 4-Syndrome: is a group of anomalies occurring together due to a common cause Chromosomal abnormalities are classified into numerical and structural deformity. PATHOPHYSIOLOGY During the first 2 weeks of development, teratogenic agents usually kill the embryo or have no effect. During the organogenesis period (3rd-8th weeks), teratogenic agents disrupt development and may cause major congenital anomalies. During the fetal period (9th week - 9th month)teratogens may produce morphological and functional abnormalities, particularly of the brain and eyes. By, Dr Jay M.Thakkar- (M.P.H, O&P,PH.D- PMR)