For a fetus to develop normally it requires a complicated interaction of genetic and environmental factors to come together in a woman’s body. The most critical period of any pregnancy is the first eight weeks during which the most important parts of the developmental process takes place: during which the zygote is created and the organs of the body begin to develop. During this period any disruption to the developmental process can result in birth defects which can be caused by the genetic errors in the embryo or by conditions of the environment to which the embryo is exposed (or both).

When considering environmental birth defects many people think of exposure to contaminated materials, harmful infections or radiation as possible risk factors but often forget that things a mother would otherwise take for granted can also be harmful including caffeine, alcohol and commonly used medicines. While the decision to use these is a personal one, they are all environmental factors that a woman subjects her fetus to during pregnancy.

The placenta is the organ that provides a fetus with nourishment during a pregnancy and anything that passes through a woman’s body from the external environment is also transferred to the fetus through the circulation of maternal blood. During pregnancy the placenta acts as the lungs, kidney and liver for the fetus and any interference or degeneration of its function can cause the fetus significant risk of abnormality. A substance that is capable of producing an abnormality in a fetus is called a teratogen but the likelihood of it happening is also impacted by a woman’s overall health, medications she is using and her overall genetic makeup. Teratogens that have been identified as contributing to birth defects include:

• Alcohol
• Tobacco
• Caffeine
• Aspirin
• Barbituates or Amphetamines
• Antibiotics
• Marijuana
• Narcotics
• Hallucinogens

Infectious diseases can also cause severe environmental birth defects so it is important to prevent them during pregnancy. These can include the following:

• Rubella (German Measles)
• Venereal diseases
• Exposure to radiation

The full range of environmental factors to which a woman is subject during pregnancy that have the potential to impact the embryo and fetus is not yet known in full and there is much that obstetricians have yet to discover. It is important for women to be aware of the potential risks and carefully weigh their personal decisions about taking any substance that has the potential to impact an unborn child during pregnancy.