The overall incidence of major malformations in the general population is between 1 percent and 3 percent, and drug exposure accounts for a similar percentage of birth defects. 3 Vitamin B6 seems to be the safest anti-emetic, but its efficacy is rather limited. B means animal studies show no risk but human studies are inadequate, or animal studies show some risk but the risk is not supported by human studies. C means animal studies show risk but human studies are lacking, or there are no studies in humans or animals. D means definite fetal abnormalities in human studies, but potential benefits may outweigh risks.
X means risks outweigh potential benefits.
Here are the FDA ratings for some drugs. Further longitudinal data is required in order to obtain a more accurate estimate. Psychological risk factors are unsubstantiated and occasionally contra-indicated yet are often discussed. While drug treatments have received much attention, none have been found which are safe and effective. Frederic Paik Schoenberg earned his Ph.D. in statistics from the University of California at Berkeley in 1997.