Pregnancy is a red flag. Simple as that for most practicioners unless there are specific physical care reasons to continue more diluted treatments. For mental care then inhalation is good and can continue anyway. Come delivery yes Jasmine at the birth.
On dilutions a 3% blend in 5 ml of carrier, 20 drops to a ml so thats
just one drop of three essential oils in the blend with higher dilutions
for children eg 10ml of carrier.
Having the evidence base to hand for each essential oil used is good
practice and these days very easily assembled as part of your protocol.
Standard stuff I know but you cant say it too often.
Caution is the word. The term emmenague is used for herbs which stimulate menstruation so naturally its best to stay away from those oils. Some oils like parsley oil are downright dangerous in pregnancy and must be avoided.
Many mums are well into the first trimester before realising they are pregnant. Some mums can tell straight away. As ever it comes down to the individual before you. If they are finding light EO inhalation supportive for conditions eg weight loss or depression before finding themselves pregnant there seems no particular reason to stop as that will be supportive of the pregnancy. Fortunately though most mums have children young so would be less likely to be using EOs for self care or pleasure so less likely to miss them.
EOs do find their way into fruit juices and bakery in particular as flavouring but obviously in tiny proportions (yes in home cooking the lemon or vanilla cake might get a good dose but you only need a little to impart the taste!).
Tiran makes a very good point that medically chemicals are avoided if at all possible during pregancy so if medication is being avoided that must also apply to EOs in any significant dose but the mum will know. Particularly in the latter stages of pregnancy the heightened sense of smell in pregnancy warns of danger. When teaching a class we warn pregnant nurses to excuse themselves if it doesnt feel right.
"Clinical Aromatherapy for Pregnancy and Childbirth" Denise Tran
Bakerink, JA. Gospe Pediatrics 98(5) 944-947 Multiple organ failure after ingesting pennyroyal
"Clinical Aromatherapy for Pregnancy and Labor" Course by RN, Aromatherapist Pam Conrad
Burns, E. "Using Aromatherapy in childbirth" Nursing Times 90 (9) 54-60
"American College of Healthcare Sciences" Aromatherapy Program, Portland, Oregon
"Clinical Aromatherapy" Jane Buckle and her Aromatherapy Course
"Aromatherapy for Health Professionals" Shirley Price