Which kinds of substances and infections can act as teratogens?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Fetal growth — human development Growth of the human fetus from the fourth month to the ninth month of pregnancy.

Teratogens are environmental agents that can cause physical defects in a developing embryo or fetus, particularly during the first trimester of pregnancy. These agents interfere with normal embryogenesis, potentially leading to structural abnormalities, functional issues with the central nervous system, growth restriction, or even fetal death.1

Teratogenic substances and agents include:

Chemical Agents: Various drugs of abuse, alcohol, and certain prescribed medications are known to be teratogenic. Specific examples include thalidomide, phenytoin, and the synthetic hormone diethylstilbestrol.1
Infections: Certain infectious diseases can act as teratogens, such as varicella (chickenpox).1
Physical Agents: Irradiation is a documented physical agency capable of producing developmental abnormalities.1
Hormonal Imbalances: Both deficiencies and excesses of fetal hormones can cause bodily defects, such as gigantism or conditions related to hermaphroditism.1

Exposure to these agents is most critical during the early stages of development, with harmful effects potentially occurring as soon as 10 to 14 days after conception.1