I do agree with Roxy that the control group in the placebo study requires more thought before it can be used as a proper control. I also agree that subjects of the study should be informed of the possibility of receiving a placebo. It could have an effect on the outcome of the study but I believe morning sickness to be a physiological condition caused by hormonal imbalance. I am very skeptical about the placebo effect as a whole but don’t see a problem with researching it further.
We can presume that a woman who volunteers for this study, in spite of the erroneous risks, would be able to handle the stress caused by the study. It seems unlikely that a perceived risk could create actual physiological risk. This appears to be equally as unfounded as the study itself. As I suggested to my group, it might be helpful to approach this study as a physician would. First and foremost, do no harm. As far as we know there are no inherent physiological risks associated with the study. My primary concern is the lack of informed consent. They are definitely not getting what they signed up for. If the perceived risk was real then consent would be a necessity.
Testing placebo hypotheses seems to be extremely difficult without informing the test subjects. I do think it could be worth studying, especially when the risks are virtually non-existent.