The following blog was written by Emilee Hughes, Certified Aromatherapist for Plant Therapy.
Over the past few months, Plant Therapy has received a surge of questions about using essential oils safely while pregnant and nursing. Today we are going to discuss the topic of pregnancy safety in depth, provide safe usage guideline SEOs, and explore our updated Pregnancy and Nursing Safe Chart.
During pregnancy, our doctors frequently ask us questions like: “What are you eating?”, “Do you consume alcohol?”, and “Are you a smoker?” This is because our growing baby receives all of its life forming nutrients from us, the mother. Whether or not we are eating right, exercising, or consuming caffeine during pregnancy can have drastic effects on our growing little one. Many of these variables have the potential to cross the placenta.
So what does the placenta do? “The primary function of the placenta in all species is to promote selective transport of nutrients and waste products between mother and fetus. Such transport is facilitated by the close approximation of maternal and fetal vascular systems within the placenta.” 
Keep this in mind:
“Essential oils by their very nature, being organic substances, will cross the placental barrier and have the potential to affect the fetus.” 
With this in mind, when choosing to use essential oils during the first trimester we recommend very limited use. This is because so much change is taking place within our bodies. In general, we do not recommend active or daily use of essential oils during the first trimester and it may be best to avoid using altogether during this time. However, to assist with nausea you may consider adding a drop of Peppermint or Spearmint to a tissue and gently inhaling to relieve some of these symptoms.
Beyond the first trimester, there are some additional variables to consider.
First let’s discuss the means of use, as we all know there are several different methods to use essential oils. Through topical application, only a small amount of oil will actually reach your bloodstream and the absorption rate is slow. Through diffusion, you will receive a small but continued dose of essential oils via inhalation. Steam inhalation offers a high but very short dose of essential oils. Lastly, when using a personal aromatherapy inhaler we receive a dose that is not as strong as steam inhalation but stronger than diffusion. 
While considering the means of use we must also reflect on how often we use essential oils. You may have heard us say with essential oils “less is more.” This is especially true when using essential oils during pregnancy. The more you choose to use essential oils, the more you will absorb, which may cross the placenta. It is best to limit essential oil usage to relieving symptoms such as fatigue, nausea, or occasional head tension. By limiting your use, you may still receive the wonderful benefits of essential oils without overexposing yourself or your growing baby.
The next thing to consider is a safe dilution percentage.
“The recommended dilution is 1% or less, for all skin applications… [For] bath[s]… [one] should add no more than 4 drops of essential oil.” 
The last and most important factor to consider is the essential oils that you are using in your blends. We must remember that “Certain essential oils are contraindicated due to the nature of their chemical components, which may be too strong (and unnecessary) for [pregnancy].” 
It is very important that you only use essential oils that are safe during pregnancy. This is where our list of Pregnancy and Nursing Safe oils will be very helpful. This list was created by our team of Certified Aromatherapists here at Plant Therapy and has been approved by world-renowned essential oil safety expert, Robert Tisserand.
There are also variables to consider when breastfeeding.
We will discuss in depth in Pregnancy and Nursing Safety – Part 2. In the meantime, if you have any questions about using essential oils safely while nursing please email an Aromatherapist at firstname.lastname@example.org.
Click Here to Download and Print the Pregnancy and Nursing Safe Chart
 Bowen, R. “Transport Across the Placenta” 6 August 2000. Retrieved 25 October 2016. http://www.vivo.colostate.edu/hbooks/pathphys/reprod/placenta/transport.html
 Christie, Deacon, Pickard, Price. “Pregnancy Guidelines: Guidelines for Aromatherapists Working with Pregnant Clients” 2013. Retrieved 25 October 2016. https://naha.org/assets/uploads/PregnancyGuidelines-Oct11.pdf
 “Aromahead Institute’s Aromatherapy Certification Program” https://www.aromahead.com/courses/online/aromatherapy-certification-program
 Smith, Anne. “Drugs and Breastfeeding” Breastfeeding Basics., Retrieved 10 October 2016. https://www.breastfeedingbasics.com/articles/drugs-and-breastfeeding
 Tisserand, R., & Young, R. (2014). Essential Oil Safety (2nd ed.). Churchill Livingstone Elsevier.