Sunday Riley Luna Sleeping Night Oil Not Suitable for Pregnant Women?

So I have been coveting a little blue bottle of Sunday Riley Luna Sleeping Night Oil since its release and today I finally have the pleasure of owning a bottle of this ludicrously priced yet much loved night time treatment. As I gleefully unwrapped it this morning, one of the first things I noticed was that the pretty dropper bottle comes complete with a very bold warning: Not for use during pregnancy.

At first this was a bit of a wtf moment - is the secret ingredient in this an intricate cocktail of booze, fags and sashimi or something else we're warned about consuming whilst with child? It sort of threw me a bit to be honest - after all, did I really want to be eagerly smothering my face with something that's actually harmful to my hypothetical foetus?

As it turns out, the potentially threatening ingredient is Trans-retinoic Acid - the very thing that makes Luna such a unique and (according to multiple reviews) effective product. Trans-retinoic Acid is basically Vitamin A and Luna is kind of special as it's a blend of natural oils and Vitamin A that makes it relatively more suitable for sensitive skins. That said, I'm yet to actually put it on my face, but I have high hopes.

So what's the issue with Vitamin A/ Retinol and pregnancy?

According to various studies, the oral consumption of excessive amounts of Vitamin A are known to cause birth defects, while the topical use of Vitamin A may be harmful to unborn babies.
I searched (googled) high and low and could not, for the life of me, find any studies that have actual, documented proof that retinol is not safe to use on your face/body if you're expecting. It seems that it's more of a precaution and hopefully wouldn't actually do any harm, unless you're literally downing bottles of the stuff.
If you've come across any studies on this, please feel free to drop a link in the comments as I'm kind of intrigued by the whole thing!

All in all, I think it's responsible of Sunday Riley to include this warning but I can certainly see that it has the potential to put some people off thinking about using the oil at all.