Twinkle Star is definitely safe to use during pregnancy! While there are essential oils that should be avoided during pregnancy, Absolute Essential (the company behind Twinkle Star) have formulated a set of oils that are completely safe to use during pregnancy. These particular oils will have the Mother & Child brand of approval, which can be seen on their website here.
The ingredients to the Twinkle Star essential oil can also be found here in the parent hub.
If you have any further concerns regarding Twinkle Star, make sure you contact your GP to confirm it is appropriate for you to use during your pregnancy.