Why is there no conclusive evidence that there is a specific amount of alcohol a pregnant woman can drink without causing harmful effects to her child?

To perform such a study would be unethical within an experimental setting. With clinical interviews, the researcher must consider the cohort effect of an untruthful answer from a participant that has engaged in alcohol during pregnancy. With naturalist or structured observations, the informed consent of the participant and privacy would be at stake. Additionally, research must performed be performed with beneficial intentions. While we have precedent set by Fetal Alcohol Syndrome cases, the determination of a percise amount of alcohol safe to drink during pregnancy violates ethical and safety concerns for baby. While most use their own digression, the safest advice healthcare workers can give to a pregnant woman is that; no amount of alcohol can be constituted as a safe amount.

The answer is false