Wrapping up you is safe as long as you don’t dehydrate or over heat yourself because that is highly dangerous. Dehydration can increase uterine activity and contractions, even though this has no effect on the cervix and cannot trigger labour but it can make you feel very nervous and nervousness is not good for the baby. So make sure that you drink a lot of water during, before and after the wrap to avoid dehydration.
More dangerous is being over heated as it can make you lose conscious plus it also raises risks of developing neural tube defects which can be very dangerous. However neural tube defects occur during the first twenty three days of a pregnancy and thus are very difficult to detect. Unfortunately due to this the defect develops even before the pregnancy can be identified.
So if you are trying to get pregnant or think that you are pregnant but are not sure then it is better to stay away from anything that can over heat your body. This does not only means staying away from seaweed wraps but also staying away from things like Jacuzzis, hot baths or any other thing that might raise your body temperature.
So to conclude this i would recommend that you should avoid getting a seaweed wrap as long as you are pregnant because it can raise your body temperature to dangerously high levels and such high body temperature in pregnancy (especially during early stages) can cause birth defects.