Many people like to take Rescue Remedy when they are anxious or more frequently, I have found, when taking a driving test or exam. There are no research studies that I am aware of. However, the Rescue Remedy site is quite reassuring.
“The Rescue Remedy® formula contains a carefully selected blend of five flower remedies and is prepared according to natural and traditional methods at the Bach Centre in Oxfordshire. While Rescue Remedy® should be safe to take even while pregnant or breastfeeding you should always talk to your doctor before taking any Rescue® product, especially if you are currently taking any medication.”
https://www.rescueremedy.com/en-us/explore/faqs/can-i-take-rescue-while-pregnant-or-breastfeeding/