Genetics

Definition

Teratogens are agents or factors that can cause congenital malformations or birth defects in the developing embryo or fetus.

Classification

Teratogens can be classified into four main categories:

• Physical: These include radiation, heat, mechanical forces, etc.
• Chemical: These include drugs, alcohol, nicotine, caffeine, etc.
• Biological: These include viruses, bacteria, parasites, etc.
• Environmental: These include maternal stress, nutrition, pollution, etc.

Grading

Teratogens can also be graded according to their potency and frequency of causing birth:-

• High-grade: These are teratogens that have a high probability of causing severe malformations or fetal death, such as thalidomide, isotretinoin, warfarin, etc.
• Low-grade: These are teratogens that have a low probability of causing minor malformations or functional impairments, such as aspirin, ibuprofen, phenytoin, etc.
• Other: These are teratogens that have an uncertain or variable risk ofcausing birth defects, depending on the dose, timing, and genetic susceptibiliw, such as alcohol, tobacco, caffeine, etc.

Examples

Some examples of teratogens and their effects are:

• Thalidomide: This is a high-grade chemical teratogen that was used to treat morning sickness in pregnant women, but it caused severe limb defects in the babies.
• Rubella: This is a high-grade biological teratogen that is a viral infection that can cause deafness, cataracts, heart defects, and mental retardation in the babies.
• Alcohol: This is an other-grade chemical teratogen that can cause fetal alcohol syndrome, which is characterized by growth retardation, facial abnormalities, and cognitive impairment in the babies.
• Cytomegalovirus: This is a low-grade biological teratogen that is a viral infection that can cause microcephaly, hearing loss, vision loss, and neurological problems in the babies.
• Iodine deficiency: This is a low-grade environmental teratogen that can cause cretinism, which is a condition of stunted growth, mental retardation, and goiter in the babies.