Harmful chemicals or viruses that can be transferred from a mother to her developing fetus are called

Teratogens are harmful chemicals or viruses that can be transferred from a pregnant mother to her developing fetus when exposed to teratogens which affect pregnancies and cause complications such as preterm labor, spontaneous abortion or miscarriages. Example of teratogen chemicals or viruses are; alcohol, tobacco smoke, mercury, lead, air pollution, pesticides, and drugs used during pregnancy. These toxicants cause low birth weight, paralysis, anemia, heart and lung problems to infants.

Tetratogens

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.