Not all of them are considered safe during pregnancy. here is the list of most common essential oils TO AVOID during pregnancy.

Anise, Bay, Basil, Camphor, Caraway, Carrot, Cedarwood, Cinnamon, Clary Sage, Clove, Comfrey, Cypress, Fennel, Hyssop, Jasmine, Juniper, Marjoram, Mugwort, Myrrh, Nutmeg, Oregano, Pennyroyal, Peppermint, Rosemary, Sage, Sassafras, Tansy, Thuja, Thyme, Wintergreen, Wormwood, Yarrow

Oils to avoid in the first trimester:

Chamomile, Frankincense, Geranium, Melissa, Rose