Teratogens and Pregnancy

A teratogen is any substance that can produce birth defects in a developing baby. It is very important for women to know what agents in their environment have the potential to harm their child. The environmental and infectious agents below fit under this classification because they harm the fetus.

Environmental Agents

Organic Mercury

Fetuses that have been exposed to organic mercury show a collection of symptoms called minamata disease. This disease resembles the neurological and behavioral similarities to cerebral palsy. Other symptoms include brain damage, mental retardation, and blindness. Exposure to methyl-mercury may cause brain damage, seizures, and mental retardation.

Lead

Lead passes through the placental membrane and is stored in fetal tissue. Exposure to large amounts of lead during pregnancy may cause increased abortions, intrauterine growth retardation, and fetal anomalies. Small amounts of exposure to lead may cause behavior problems and psychomotor disturbances in small children.

Polychlorinated Biphenyls (PCBs)

PCBs may cause intrauterine growth retardation and skin discoloration. PCBs are found in fish caught in contaminated waters.

Radiation

Exposure to high amounts of radiation during pregnancy may cause problems with mental development and physical abnormalities. The amount of damage caused by radiation depends on the absorbed dose, dose rate, and stage of development of the fetus. Some other abnormalities include changes to the retina pigment, cataracts, and cleft palate.

Infectious Agents

Rubella

The risk of passing rubella to an unborn fetus is 20%. The collection of symptoms is called congenital rubella syndrome. These symptoms include cataracts, cardiac defects, deafness, mental deficiencies, glaucoma, and tooth defects. The most vulnerable time for the unborn child is 4-5 weeks after fertilization.

Cytomegalovirus

Cytomegalovirus may cause spontaneous abortion when exposed early in pregnancy. Later on in pregnancy, Cytomegalovirus may cause IUGR, eye deformities, mental retardation, CNS abnormalities, and deafness. Asystomatic CMV infection may cause audiological, neurological, and neurobehavioral abnormalities.

Herpes Simplex Virus (HSV)

HSV triples the abortion rate of the unborn fetus. HSV also increases the rate of prematurity of the unborn fetus. Infection late in pregnancy may cause cutaneous lesions, microcephaly (small head), eye problems, and mental retardation.

Toxoplasmosis

Toxoplasmosis is caused by the organism Toxoplasma gondii. It can be contracted by eating poorly cooked meat with Toxoplasma cysts, getting close to infected domestic animals, or soil. If the unborn fetus contracts Toxoplasmosis, the unborn child may experience CNS problems, eye problems, and hydrocephaly (water on the brain). Toxoplasmosis may cause death if it happens early in pregnancy.

Congenital Syphilis

Congenital syphilis is caused by the organism Treponema pallidum. Infection may cause serious fetal anomalies, and one-fourth of children born with syphilis are stillborn. Early manifestations of syphilis may cause deafness, teeth and bone abnormalities, hydrocephalus, and mental retardation. Late manifestations of syphilis may cause facial abnormalities and dental abnormalities.

Works Cited

Moore, Keith, and T.V.N. Persaud. The Developing Human Clinically Oriented Embryology. Philadelphia: Saunders, 2003.