Chemical Agents

There are many chemicals that can cause fetal abnormalities by crossing the placenta and entering the fetal blood stream. Some of these are naturally occurring substances, others may be drugs. 

Smoking during pregnancy

Cigarettes contain 1000s of chemicals. Some of these are known carcinogens and others such as nicotine are addictive. Because of the large number of compounds it can be difficult to know exactly which chemical causes certain effects. It is known that babies’ of smokers are born with a much lower birth weight. Fetuses with a lower birth weight are more susceptible to miscarriage. There is also constriction of blood vessels so that the amount of oxygen passing into the baby in decreased and this may in turn cause changes in the brain. There are links with the children of smokers having short attention spans, or hyperactivity and well as slow mental development. There are also studies linking an increased incidence of cleft lip in babies to mothers that smoke.

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Illegal drugs during pregnancy

It can be difficult to obtain reliable information on illegal drug use and the effects on the developing fetus as more users will use many different substances, smoke or drink alcohol. There has been some research into cocaine use.  Most problems during pregnancy are associated with regular use of cocaine although some reports suggest that even one use can have severe effects. As well as babies being born with low birth weight and shorted body length, there are also risks to most of the body including heart, brain, skull, face, genitals and GI tract.

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Anticonvulsants

The use of anticonvulsants during pregnancy to treat maternal epilepsy can cause fetal abnormalities. About 10% of children exposed to Dilantin will have hypoplasia, metal retardation and a characteristic face. The use of another drug valproic acid has a 1% chance of causign spina bifida. There is also some controversy to weather or not exposure to benzodiazepines increases the risk of cleft lip and palate. Some anticonvulsant medication can cause anencephaly.

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Cyclopamine- An animal model

Although it has not been studied in humans to a great extert, many sheep grazing on corn lily in Idaho gave birth to cyclopic offspring. It was discovered that the active ingredient, cyclopamine, interfered with fetal patterning by disrupting Hedgehog signaling in the embryo. Although during pregnancy it can act as a teratogen, it is possible that cyclopamine may provide a possible therapeutic route for cancers which are caused by over active hedgehog pathways.

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