- These are chemicals or drugs causing malformed foetus.
- The production of monsters or malformed foetus is called tertogeny or teratogenesis.
- The ability of a drug to cause foetal abnormalities when used by pragnant women is termed teratogenicity.
- Study of malformed babies is known as teratology.
- Teratogens may affect embryogenesis by disturbing one or more development processes.
- They may cause over developed & under development of tissue or organs.
- There are three main categories of teratogens -
1. DRUGS AND CHEMICALS -
(i) Alcohol may cause foetal alcohol syndrome (FAS). It includes deficient prenatal growth, facial abnormalities, mental retardation.
(ii) Thalidomide may cause phocomelia i.e. hands & feet are attached close to body, resembling the flippers of a seal, ear anomalies, cardiac malformation, closed oesophagus, failure of kidney development.
(iii) Diazepam (Valium) use increases the risk of oral cleft.
(iv) Halucinogens - THC causes birth defects, LSD produces chromosomal & foetal abnormalities.
(v) Quinine (Malaria), bubulphan (Leukemia), chlorambucil (Hodgkin's diseases) aminopterin (abortion) seriously harm the foetus.
(vi) Tetracycline increases susceptibility to caries, streptomycin increase susceptibility to hearing loss.
(vii) Epileptic woman should discontain anticonvalsant drugs (Dilantin) during pregnancy as it causes foetal hydantain syndrome (FHS) characterised by poor prenatal growth short limbs, mental retardation, facial anoma- lies, cardiovescular abnormalities.
(viii) Many pragnent woman take progestin or estrogen to avoid abortion. Use of these hormones causes masculinization of the ext. genitilia in female foetuses.
If hormone cortisone and vit. A taken in excess during early pregnancy, cause foetal defects such as hydrocephalus (very large head).
(ix) Tobacco smoking by pregnant women leads to poor foetal growth & increases risk of abortion, intrauterine foetal death, neonatal death and premature birth.
2. INFECTIOUS AGENTS -
Viral, bacteria and parasitic infections may cause serious effect on foetus.
3. RADIATION -
Exposure to ionizing radiation of 2 to 6 weeks old foetus is teratogenic. It may cause pregnancy loss, growth retardation, eye malformation and CNS defects.
May cause mutation and leukemia.