Name one essential oil that is contraindicated for use during pregnancy.

Sage essential oil is contraindicated for use during pregnancy primarily due to its high thujone content, which can stimulate the uterus and potentially lead to complications such as miscarriage. During pregnancy, it is crucial to avoid any substances that may induce contractions or pose risks to the developing fetus.

In contrast, lavender essential oil is often considered safe in moderation during pregnancy, as it is known for its calming and soothing properties. Sweet orange essential oil is also regarded as safe and can even help with mood enhancement. Frankincense essential oil has some potential benefits during pregnancy; while it is recommended to use it with caution, it is not widely labeled as contraindicated. Thus, sage oil is the one that stands out due to its specific risks during pregnancy.