It is recommended that you do not use essential oils at all during your first trimester.
The first twelve weeks of pregnancy form the important developmental phase for your unborn baby and whilst there is no solid evidence to suggest that the use of essential oils will hinder this, there is also no solid evidence to suggest that they will not either.
Essential oils during your second and third trimester are a great way to relax and alleviate some common pregnancy complaints.
From constipation to fatigue, there are numerous pregnancy ailments that you can avoid through the careful use of essential oils.
Which essential oils can I use during pregnancy?

• Lavender: Lavender can be used to treat migraines and headaches.
  It has great relaxing properties, so if you are finding that you can't sleep despite feeling fatigued, add a few drops of lavender oil to your pillow before bed time.
  It can also be used as an anti-septic, which is great for women who are suffering from rectal bleeding due to pregnancy constipation and piles.
  Women with SPD may find it useful for alleviating back pain and those who are having trouble with their water works can use it to stimulate urine production.
  If you are suffering from a pregnancy cold, use lavender oil as a natural remedy to treat it.
  
• Mandarin Oil: Much like Lavender Oil, Mandarin has great anti-septic properties, so if you don't care for the strong scent of lavender and fancy something more uplifting, use Mandarin to soothe sores and cuts caused by pregnancy constipation and piles.
  It can also relieve colds, coughs and respiratory problems and will assist with cramps and ensure you maintain correct liver bile function.
  It's uplifting citrus scent is great for providing you with a mood boost if you are feeling low.
  
• Ylang Ylang: Ylang Ylang is well known for relaxing you and instilling a general sense of peace and well being.
  It can be used to combat depression, anxiety and nervous tension.
  
• Neroli Oil: If you are suffering with pregnancy diarrhea, Neroli Oil may be able to settle your digestive tract and regulate your bowl movements.
  It is also great for women suffering from depression, shock, stress or fear during their pregnancy.
  

How do I use essential oils during pregnancy? There are several ways you can use essential oils during your pregnancy:

• Add 5-6 drops to your bath water and mix in well before getting in.
  
• Add 3 drops to a bowl of warm water, soak a flannel in the mixture and rinse well.
  Use the flannel as a compress whilst relaxing.
  
• Add 4 drops of essential oil to 2 teaspoons of a carrier oil and use it in your usual burner.
  
• Add 2-3 drops of your chosen essential oil to your pillow before bed time.
  

Before using Aromatherapy during your pregnancy...
You must consult with your midwife or OB in advance.
All low risk women and the majority of high risk women should be okay to use aromatherapy during pregnancy, however there may be a reason why your particular pregnancy will not allow for the safe use of essential oils.