Essential oils can provide many benefits during pregnancy (such as relieving back pain and ankle swelling, and reducing stretch marks) and while breastfeeding, but there are special precautions to take and particular oils to avoid at these times.
Like many other aspects of Aromatherapy, there is still a lot of research to be done in terms of the potential risks of using essential oils while pregnant or breastfeeding. According to the National Association of Holistic Aromatherapy (NAHA), the biggest concern during pregnancy is that the oils will cross over into the placenta. Developing embryos and babies are much more sensitive to these oils than their mothers. These precautions are especially important during the first trimester, the time when the fetus is most susceptible.
In most cases, essential oils are safe to use at these times, particularly in very small doses—such as a few drops of Lavender in a bath at night. It is recommended to avoid large doses.
Here is a list of some recommended oils, and ones to avoid. Please note that the following lists are NOT complete, and it is recommended that you consult with your personal care provider prior to using essential oils during pregnancy or while breastfeeding.