Exposures and Risk Factors

When discussing exposures and risk factors in regards to birth defects, we are talking about anything the fetus is exposed to as well as anything that may alter conditions within the womb. This includes everything the mother may come into contact with during pregnancy. Because most structural development of the fetus occurs during early pregnancy, we focus on what is called the "periconceptional" period - the month before and first 3 months after conception.

• Exposures – anything that comes into direct contact with the mother or fetus
• Risk factors – such as social or economic conditions, may provide clues that can help pinpoint causes.

Studies cannot always provide a definitive answer about whether a particular exposure, risk factor or both caused a birth defect. Instead, results are reported as changes in birth defects risk for exposed pregnancies compared to unexposed.

• Higher risks – a doubling or more – suggests an association between the exposure and the condition in question. This may mean the studied exposure/risk factor contributes to the birth defect.
• Decreased risks – one half or less – indicates a protective effect. The exposure appears to prevent the birth defect from occurring.
• No change in risk – implies that the exposure and the defect are not closely related.

Studies that are conducted in order to discover the role of exposures and risk factors on birth defects must validate biologically plausible pathways of exposure – in other words, ways the mother could have been exposed. Proximity is not enough. If a pregnant woman lives near a source of environmental concern, for example, it must also be taken into consideration whether she could have inhaled, ingested or otherwise been exposed to harmful conditions.

The following is a list of exposures and risk factors that may have some impact on a fetus if the mother was exposed during pregnancy:

• Air pollution
• Alcohol
• Chemicals, pesticides and solvents
• Diet and Nutrition
• Drinking Water
• Drugs
• Folic Acid / Vitamins
• Medication

Additional Resources