According to Canada.com:
If you love a hot bath - especially when the wind is howling outside - the bad news is that hot water can aggravate and, surprisingly, even dehydrate your skin. So if you do run a bath, use warm (not hot) water, and try to limit your baths to only a few times a week.
I was recently asked if taking hot baths was dangerous during pregnancy.
Here is Dr Phil's answer:
Women are told not to take baths because HOT water — over 98 degrees — is unfavorable to the pregnancy. Taking a warm (NOT HOT!) bath with someone to help you get in and out of the bath safely can help:
* Decrease uncomfortable swelling in arms and legs.
* Increase the amniotic fluid.
* Prevent premature contractions.
Help the mother relax and alleviate anxiety about the health of her baby.
This is also why swimming is such a great pregnancy exercise.
For a relaxing bath, we recommend using 6 drops of lavender essential oil.
For a stuffy head cold, we love a bath with 6-10 drops of eucalyptus essential oil.
Be sure that you use real essential oils and not fragrance oils. Also, it only takes a few drops in the bath to create a beautifully scented bathing environment. As with anything, use essential oils carefully, keep out of reach of small children (some oils are very toxic), and do not substitute for proper medical attention.
For more on essential oils, we recommend The Complete Book of Essential Oils and Aromatherapy by Valerie Ann Worwood.