Birth defect and poor environment

 

 

What are the different manifestations of drug insult / environmental insult??  Ans; This may be  effected as  A) abnormal development B) as death C) diff  kinds of  malformation D) growth restriction and above all F)  functional disorder ?

Ans: Same teratogen may have one effect A) if exposure occurs during embryogenesis and B) different effect  if the exposure is during the fetal period. Embryonic exposure is likely to lead to structural abnormalities or embryonic death; fetal exposure is likely to lead to functional deficits or growth restriction.

Despite the importance of teratogen timing on specificity of anomalies a general pattern usually emerges with respect to any given teratogen. This will be evident throughout this chapter as we consider various agents. If no pattern is evident for a purported teratogen, it increases the suspicion that any purported association is spurious the observation reflecting confounding variables not recognize and hence not taken into account.

Ill effects on  adverse environmental influences on embryo or foetus:  Adverse environmental influences to developing tissues depends on the nature of the influence . This principle relates to such pharmacologic factors as maternal metabolism and placental passage. Although most clearly understood for chemical agents or drugs the principle also applies to physical agents such as radiation or heat. For an adverse effect to occur an agent must reach the conceptus either transmitted indirectly through maternal tissues or directly traversing the maternal body.

Dose Effect : The final principle is that manifestations of abnormal development increase in degree from the no-effect level to the lethal level as dosage increases. This means that the response may be expected to vary according to the dose duration or amount of exposure. For most human teratogens, this dose response relationship is not clearly understood but along with the principle of critical stages of development these concepts are important in supporting causal inferences about human reproductive hazards. Data regarding in utero exposure to ionizing radiation clearly show the importance of dose on observed effects for teratogens has been noted.