A few common teratogens and their effects

Tobacco

Exposure to tobacco common through smoking cigarettes or otherwise ingesting tobacco or being the recipient of second hand smoke. The risk to a developing fetus, whose mother is exposed to tobacco, is that the placenta may not develop normally causing conditions like a placenta previa that can cause severe complications, including death, during pregnancy and/or delivery. The fetus is also at increased risk of developing heart defects and being born at a low birthrate.  Babies that do survive are often difficult to comfort and are sometimes described as nervous or "jittery".  Another tangential point is that babies that continue to be exposed to tobacco (second hand smoke) after birth have increased risk of SIDS, asthma, and other lung related problems.[8]

Alcohol 

Fetal Alcohol Syndrome. Fetal alcohol syndroe (FAS) is a pattern of mental and physical defects that develops in some offspring when exposed to alcohol in utero. The first trimester is the most susceptible period. Some babies with alcohol-related birth defects, such as lower birth weight and body size and neurological impairments, do not have all of the classic FAS symptoms. These outcomes are often referred to as fetal alcohol effects (FAE). Currently there is not total agreement among medical scientists concerning the precise differences between FAE and FAS. In addition to growth retardation, the most common outcomes of fetal alcohol syndrome include psychomotor dysfunction and craniofacial anomalies.

The observed growth deficiences are associated with an inability of the baby to catch up due to a slower than normal rate of development. Other infrequent outcomes include skeletal malformations such as deformed ribs and sternum, scoliosis, malformed digits, and microcephaly. Distinctive facial anomalies have been associated with a diagnosis of fetal alcohol syndrome: small eye openings, epicanthal folds, failure of eyes to move in the same direction, short upturned nose, flat or absent groove between nose and upper lip, and thin upper lip. Visceral deformities may also be present: heart defects, genital malformations, kidney, and urinary defects.

A common concurrent manifestation of FAS include central nervous system defects. These include irregular arrangement of neurons and connective tissue. Mental retardation may also be present and associated with learning disabilities as well as difficulties in controlling body coordination.[9]

Accutane (Isotretinoin)

Accutane is a member of a family of drugs called retinoids, which are related to vitamin A. It is approved to treat serious forms of acne. These painful and disfiguring forms of acne do not respond to other acne treatments. Accutane is a prescribed medication that controls and prevents some of the mechanisms in the glands that contribute to acne. Accutane is very effective, but its use is associated with a number of risks including birth defects. Exposure of pregnant women can lead to birth defects such as facial malformations, heart defects, and mental retardation. This is an extraordinarily dangerous substance for a developing foetus.[15]

Thalidomide 

Thalidomide was identified as a human teratogen 20 years ago. Compared to other teratogens, thalidomide's selective toxicity in the embryo, particularly for the developing limbs, and its relative lack of toxicity in the adult is striking. [10]

Thalidomide is famous teratogen.  Thalidomide is a sedative-hypnotic drug used in Europe from 1957 to 1961. It was marketed for morning sickness, nausea, and insomnia. It went into general use and was widely prescribed in Europe, Australia, Asia, Africa, and the Americas. Women who had taken the drug from gestation days (GD) 35 to 50 gave birth to offspring suffering from a spectrum of different malformations, mainly amelia (absence of limbs) or phocomelia (sever shortening of limbs). Other malformations included: absence of the auricles with deafness, defects of the muscles of the eye and face, and malformations of the heart, bowel, uterus, and the gallbladder. The compound was withdrawn from the market in 1961 after about 10,000 cases had occured.[9] 

PAHs

Polycyclic aromatic hydrocarbons (PAHs) are a group of over 100 different chemicals that are formed as byproducts of combustion (burning) of coal, oil, gas, garbage, tobacco, foods and other organic substances. Benzo[a]pyrene (BaP) is the most toxic and best studied of the PAHs.  Naphthalene is a type of PAH used in mothballs and some cleaners. In test animals exposed during pregnancy, BaP has caused reduced viability of litters, decreased birth weight, and cancer and reduced fertility in offspring.[11]

 

Mercury

Mercury is a shiny silver metal that is in liquid form at room temperatures.  Exposure to mercury might happen around broken thermometers, dental fillings, broken florescent light bulbs and eating fish that have high levels of mercury (especially swordfish, shark, king mackerel and tilefish).  A fetus, whose mother is exposed to mercury, could be in serious danger.  Mercury can stop the duplication process of cells and lead to the death of the fetus.  It can also alter the cells as the divide and introduce a variety of unpredictable mutations in the developing fetus, especially to their nervous system. [8]

Ethidium bromide 

Ethidium bromide (EtBr) is widely used for rapid visualization of nucleic acids in electrophoretic gels.  EtBr forms fluorescent complexes, by intercalation of DNA, which are readily visible under ultraviolet (UV) light. EtBr is strongly mutagenic (a frameshift mutagen).  Although there is not enough evidence yet to classify EtBr as a human carcinogen or teratogen, this material must be considered a possible carcinogen and reproductive toxin.  EtBr is highly toxic by inhalation (R26), particularly in powder form, and is irritating to the skin, eyes, mucous membranes and upper respiratory tract.[12]

Radiation

There are a number of ways to be exposed to radiation: having a medical X-ray, working at a nuclear power plant, working in any industrial setting where X-rays or other radioactive substances are used, nuclear accidents (like Chernobyl) nuclear bomb detonations (testing or the Japanese wartime explosions) and countless other minor sources like TVs, smoke detectors, and airplane trips.  Radiation exposure at high enough levels can cause developmental risks to a developing fetus like a reduction in height, severe mental retardation, small head size, impaired brain development, childhood leukemia, and cancer in later life.[8]

Toxoplasmosis

Toxoplasmosis is an infection caused by a microscopic parasite called Toxoplasma gondii. Although the infection generally causes a mild, symptomless illness in people with healthy immune systems, it's risky during pregnancy because the parasite may infect the placenta and  unborn baby. This infection can be mild or severe, causing stillbirth, long-term structural and neurological damage, and other devastating effects. Experts estimate that about half of toxoplasmosis infections are caused by eating raw or undercooked infected meat, but you can also get the parasite by eating unwashed contaminated produce, drinking contaminated water, or handling contaminated soil, cat litter, or meat and then touching your mouth, nose, or eyes.[13]

HIV

HIV is the virus that causes AIDS (acquired immune deficiency syndrome).  A person typically becomes infected with HIV by having vaginal or anal sex (especially unprotected sex) with a carrier or being exposed to infected blood (most often by sharing needles) - There are other, more atypical, methods of exposure like oral sex and blood transfusions.  The health risk to a developing fetus, whose mother is infected, is that they will contract the virus themselves (congenital HIV) sometimes spontaneously aborting or surviving but being born infected with, the currently incurable, HIV.  Being born infected with HIV is probably the most common birth defect in the world today.  Medications to reduce the virus levels in the mother's blood and a short delivery by caesarian can greatly reduce the risk to the baby.  An infected mother can pass the virus on to her baby during breastfeeding.[8]

Iodine Deficiency

Iodine is required for the production of the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). These thyroid hormones regulate growth, development, metabolism, and reproductive function in all age groups. Fetal and child development suffers the greatest impact from low levels of thyroid hormone and the greatest risk of iodine deficiency disorders.

During pregnancy, thyroid hormone production increases by 50 percent; this requires a greater intake of iodine to maintain thyroid function and thyroid hormone production.

At 11 weeks of fetal development, the fetal thyroid gland begins to function and is producing its own thyroid hormone by 18 to 20 weeks. During this time, and up to the third year of life, iodine intake is crucial for the mother and child. In the developing fetus, the brain is rapidly growing and the nervous system developing. If iodine is unavailable or in short supply during pregnancy and lactation, there is a likelihood of irreversible brain damage and other iodine deficiency disorders.[14]