I can't profess to know much about aromatherapy oils but one essential oil I know MUST be avoided by expectant mothers or women planning to conceive is Lavender. Please, avoid it like the plague. Don't use it it oil burners, baths, pot pourri, perfume - anything. It's highly potent, enough to cause a miscarriage and was probably the cause of my work colleague's stillbirth after her midwife told her to use it during her pregnancy.