During a patient's first visit with me, I often tell them that when it comes to preconception and prenatal care, I believe we need to take a precautionary approach.
Per the Canadian Environmental Law Association,
"The precautionary principle denotes a duty to prevent harm, when it is within our power to do so, even when all the evidence is not in."
As I've mentioned before, using a cigarette smoking as an example, there are numerous instances in medical history where something had been shown or seriously suggested to be true in early medical research, but society (or the medical community) was slow to adopt this information. It matters because when we don't seriously consider the new facts as they become available, we fail to prevent or reduce suffering and harm among the population.
We don't always have the "gold standard" available when it comes to research and sometimes this is why we see a reluctance to consider and apply the results.
A perfect trial would be a double-blinded, placebo controlled randomized controlled trial. In these studies, women would be blindly divided into 2 groups, and one group would be exposed to a theoretical toxicant and the other group would receive a placebo. We would then follow their pregnancy and their offspring and see if those that were exposed were noticeably (and more significantly) affected.
The problem with waiting for this kind of research quickly becomes clear. Once we have some early indication that exposure to a chemical such as BPA may be dangerous in pregnancy, it becomes unethical to willfully expose a group of pregnant women to this (or any other similar) chemical, just in order to achieve this "gold standard" of research.
So we have to do our best with the research available. Perhaps we don't turn our lives upside down when one new study is published, but when we have consistent, repeated research all pointing in one direction, it makes sense to take it seriously and start to make relevant changes.
I like this description published in Environmental Health Perspectives:
"The precautionary principle...has four central components:
taking preventive action in the face of uncertainty; shifting the burden of proof to the proponents of an activity; exploring a wide range of alternatives to possibly harmful actions; and increasing public participation in decision making."
In PCC, we focus our efforts on points 1&3. We seek to prevent exposure given the uncertainty (though certainly slanting towards harm) and we examine, practically, how to do that with alternatives.
References
The Precautionary Principle. (n.d.). Retrieved from http://www.cela.ca/collections/pollution/precautionary-principle
Kriebel, D., Tickner, J., Epstein, P., Lemons, J., Levins, R., Loechler, E. L., . . . Stoto, M. (2001). The precautionary principle in environmental science. Environmental Health Perspectives, 109(9), 871-876. doi:10.1289/ehp.01109871