Can Vibrations Harm a Fetus?
The things we know about the effects of vibration on a fetus is related to long-term exposure, similar to those generated by a jackhammer or other work-related activities. A study was done 20 years ago and it revealed that vibration from these sources could increase the risk of miscarriage, stillbirth or damage to the baby. Experts advise pregnant women to avoid long term use of whole body, low frequency vibration.
Massage chairs are not the only source of vibration that a pregnant woman can be exposed to, others include roller coasters, sex, driving or being a passenger in a car, vibrators (sexual stimulators), etc.