The following info was taken from the FB group Betsy Bosom for Oils, Pregnancy, & Nursing Moms. This group is a GREAT resource to head to and use the search bar for any specific questions you have related to oils and pregnancy!
Oils to Use with Caution
Buckle up - Because this one is a doozie.
This was probably the most controversial chapter I wrote, and I kid you not I spent hundreds of hours studying up on the oldest traditional recommendations, as well as modern and current findings. Everyone's "Safe list" and "Cautious list" is different. How to decide?
To get the best perspective, I do what I did when my phone stops working. I threw it out the window. Maybe with a few specific words. Maybe.
After I threw everybody else's "list" out the window, I did what I do best - RESEARCH. I looked into old traditional practices as well as the most modern and current data. I then compiled all the reasons why an individual may or may not use a particular oil.
I believe this puts you in control of your own choices. Again, I do not give a safe list and an unsafe list. I break oils down into 3 categories, oils to use confidently and thoughtfully, oils to use with caution, and Avoid during pregnancy.
The image is a quick list. And yes. It may be different from another list floating out there on the internet. Here is WHY I feel these oils may be used with Caution - meaning if they are a better choice than a synthetic, they are appropriate for the situation, and they are used correctly and not excessively. No accidental deaths to a mother or fetus have ever been correlated to using these essential oils while pregnant, so long as the mother uses them correctly according to the directions on the bottle. Harm has been reported by abusing or using them in excess.
Here we go.
_____________________________________________________________
* Be cautious using oils high in 1,8 cineol.
The constituent 1,8 cineol is also known as Eucalyptol and is abundant in Cajeput*, Rosemary Cineol, Ravensara, Ravintsara, and several species of Eucalyptus. (Eucalyptus Globulus, Eucalyptus Polybractea*and the more commonly known Eucalyptus Radiata). Rosemary Cineol carries the long botanical name Rosmarinus officinalis CT 1,8 cineol and is commonly written as Rosemary ct, Rosemary Cineol, or simply “Rosemary.” The botanical name helps to identify it as the high Eucalyptol species, and also to separate it from Rosemary Verbenon, (Rosamarinus officinalis, ct verbenon) another species in the same family. Rosemary ct contains up to 55% 1,8 cineol while Rosemary Verbenon contains less than 15% of the constituent 1,8 cineol. Oils containing 1,8 cineol are fantastically mucolytic and are favorites for respiratory support, especially during the winter. They support open, clear airways and healthy breathing with less concern than that of the camphorated oils. However, 1,8 cineol can be toxic in high doses. Also, while it is used to support and clear the respiratory system, it may have an opposite congesting effect when used too strongly near the noses of children. Oils like Rosemary ct are more concentrated than the herb, therefore take a very small amount to use for cooking or in internal applications. Overuse of these oils is not recommended and should be used as needed, rather than wearing or diffusing daily. Keep in mind that small amounts of these oils properly diluted, or small amounts blended into a synergy, is not considered excessive. For example, Thieves blend contains a small amount of Rosemary ct and is further blended into a balanced synergy that is designed to support the immune system. Diluting these oils, and using them only as needed, will ensure that they can be enjoyed as necessary, but not overused.
____________________________________________________________
*Be cautious using oils high in Menthol.
Peppermint is the big one here with over 52% Menthol. Spearmint and Ravintsara also contain Menthol. This minty-hot constituent has been synthetically duplicated in many personal care applications, and I always prefer natural to synthetic. However, Menthol can be a little harsh in a time where I try and use the most gentle oils available. During pregnancy, the minty Menthol may cause discomfort to the baby’s developing eyes. While there has never been reports of a baby or a baby’s eyes being harmed by Peppermint over the abdomen, there is evidence that it causes discomfort. Just as you do not like Peppermint near your eyes (Have you ever touched your eye after applying Peppermint?! Ouch!!), babies show signs of discomfort when Menthol is near the abdomen. They will pull their faces away from an abdominal area where Peppermint has been applied. This fetal discomfort is 1) just plain sad and 2) can cause the baby to turn into an undesirable position. For this reason, I suggest using a more mild oil when available, and avoiding Peppermint topically around the abdomen. Diffusing Peppermint can be a natural way to ward off smell sensitivities during pregnancy and it doesn’t get near the fetus’s eyes.
Conversely, topical abdominal application is sometimes used by midwives to turn a baby who is breech. Turning techniques are used where diluted Peppermint is applied at fundus (top of the uterus), and a heating pad towards the cervix. Breech babies will oftentimes pull away from the cold, minty Peppermint and towards the warmth. I’ve seen this successfully employed several times, and wish every woman with a breech pregnancy knew to try this simple technique before having a C-section. If you wish to turn a breech baby with this technique, be sure to speak to a midwife or care provider who is familiar with flipping breeches with oils – they can best advise you how much oil is appropriate for your body.
______________________________________________________________
Be cautious using oils high in Euganol.
Euganol is a constituent found in Cinnamon bark, Cassia, and Clove. Euganol is a natural oral numbing agent and works wonders for holistic oral care. People love Euganol for natural dental care and is often used (diluted) for teething and mouth support when the oral tissues are stressed. Euganol has also been shown to slow blood clotting, which is good for those seeking blood thinning, but on the flip side this causes concern for bleeding when nearing delivery. No reports of harm have been made when using Cinnamon Bark, Cassia or Clove in small, food-typical amounts. Studies have shown lung hemorrhaging and pulmonary edema in rats who were injected with large quantities of isolated Eugenol. While this doesn’t translate to real world scenarios, it does imply that excessive use of Eugenol could aggravate bleeding. Interestingly, it’s important to point out that isolated constituents work differently in the body than an essential oil containing that alongside other constituents, which may have a balancing effect. For example, in another study, Cinnamon had coagulant properties and prevented hemorrhaging.
Cinnamon bark has a plethora of studies showing antimicrobial action, which may be of benefit to keeping a pregnant mother healthy. These oils are also known as “hot oils” containing Cinnamaldehyde, which can be caustic to the skin, therefore they should be diluted before use. Dilute these oils or blend with other oils to balance the Eugenol and Cinnamaldehyde when using topically and avoid excessive use near delivery. Intermittent diffusion of a BLEND like Thieves is one way to prevent overexposure. When using topically or internally, I suggest to use sparingly, diluted, and only as needed. Occasional use of Thieves for immune support or sensitive teeth does not carry the same concerns as large amounts of Clove or Cinnamon bark neat.
_____________________________________________________________
*Be cautious using essential oils high in Trans-anethole / E-anethol.
E-anethole is an ether that is present in high levels (more than 45%) in the oils of - Fennel, Bitter Fennel*, Anise*, Star Anise*, and Myrtle. This is a sweetening and flavoring agent and is listed with a GRAS status (generally regarded as safe) by the FDA for flavoring purposes. It has been shown to assist with digestion by restoring delayed gastric emptying in rodents. With anything that has the potential to be helpful, it also has the potential to be harmful when not used correctly. Studies that show benefit or harm are largely dose dependent. Excessive ingestion of E-anethole has been linked to toxicity in the liver in some cases. Yet, Sweet fennel oil demonstrated potent hepatoprotective action against liver injury in rats in another study. 3
Isolated E-anethole has been a concern for teratogenicity, being toxic to fetal cells or preventing implantation. Fennel oil was tested in-vitro (in a dish) on rat embryo limb buds. The oil inhibited the limbs from growing, raising concern that Fennel oil could possibly cause birth defects. It was later determined that this was due to cytotoxicity, resulting from exposing the cells directly to the essential oil. It was concluded that Fennel oil, at certain concentrations, is toxic to fetal cells, but does not impact normal development. This would mean that there would not be the same teratoxic concerns when using Fennel in applications such as cooking. When applied topically, it would absorb into the bloodstream and be transferred via the placenta rather than placed directly on the cells.
More importantly, E-anethole may impact Estradiol levels when used daily. Children consuming fennel tea on a daily basis showed significantly higher Estradiol serum levels than those who did not. Because we don’t want to significantly alter our Estradiol levels during pregnancy, this may be the most common sense reason to limit the use of oils like Fennel or Myrtle while pregnant. Small food typical amounts have not been shown to cause harm, but you may choose whether to use these oils sparingly, or put them on hold until later.
_____________________________________________________________
*Be cautious with excessive use of Essential Oils high in Methyl chavicol or Carvacal.
Here we have a few more common herbs that are typically ingested safely by the general population, but may have negative effects when used excessively. Methyl chavicol is in the Estragole family and Carvacal is in the Phenol family. These constituents are found in several herbs such as Basil, Tarragon, Oregano and Mountain Savory. A report of the European Union, Committee on Herbal Medicinal Products wrote that isolated Methyl chavicol is carcinogenic in large amounts. In rodent studies, the events were largely dose dependent, and the harm was minimal until doses of 100-1000 times typical food consumption were reached. The study concluded that the exposure to Estragole resulting from consumption of herbal medicinal products (e.g. short-time use in adults at recommended amounts) does not pose a significant cancer risk. Good news! You probably won’t die from pesto! Estragole is found in Basil leaves and is quite concentrated in pesto. However, the WHO has declared pesto to be safe for human consumption because research has shown that anticarcinogens in Basil leaves counteract the toxic effects of the carcinogens. This shows that studies using high levels of an isolated constituent does not necessarily translate to the real world. Out of caution, the exposure of Estragole to sensitive groups such as young children, pregnant and breastfeeding women is recommended to be minimized to typical food exposure, while limiting excessive therapeutic doses.
_______________________________________________________________
*Be cautious when using essential oils that may impact hormones.
Positively impacting progesterone levels are not as much a concern in pregnancy, since Progesterone levels skyrocket to very high levels. The follicle that releases the egg is called the corpus luteum. It releases Progesterone to help thicken and prepare the uterine lining for implantation and if an egg is fertilized, it continues to release Progesterone until the embryo has attached. Progesterone is important because it plays a part in maintaining the pregnancy until birth. If the corpus luteum fails to produce enough Progesterone, this may result in pregnancy loss. For this reason, some women closely monitor their Progesterone levels before trying to conceive and throughout their first trimester. Oils that support healthy progesterone levels (such as Progessence Plus™ Serum) are not considered dangerous during pregnancy. (See Jordan’s Schrandt's fertility story in the Real Women section of the Baby book or go check out our live interview in the Lucy Libido group for a tear-jerker)
Some essential oils may influence the Estrogen levels in your body. This can be fantastic for ovulation health and hormone support when trying to conceive (Hello Lucy book!) but they aren’t recommended during pregnancy. Oils that may positively influence Estrogen levels are Sage, Clary Sage, Sage Lavender, Fennel, and some blends to be aware of are Lady Sclareol, SclarEssence, and Dragon Time.
Use these to support conception, but discontinue use after a confirmed pregnancy.
_____________________________________________________________
All the cited studies and full information is in the Oils During Pregnancy of the Betsy Bosom Baby Book. Another great book resource that I highly recommend is Gentle Babies.