As others have said I think it is about Vitamin A. I googled it and found this...
The average diet provides plenty of vitamin A. It's available in meat, dairy, fish, eggs, and fortified cereals in the form of preformed vitamin A, or retinol. It's also in most fruits and vegetables, mostly in the form of carotenoids.
It's important during pregnancy not to get too much of the preformed vitamin A, which in high doses can cause birth defects and liver toxicity. (You can take in as many carotenoids as you want from fruits and vegetables.)
It's not a good idea to double up on your prenatal vitamins or take any supplements that your practitioner doesn't recommend because most prenatal vitamins contain at least part of their vitamin A in the form of beta-carotene, but some over-the-counter brands, multivitamins, and some fortified foods contain significant amounts of preformed vitamin A, so check the labels or show them to your practitioner before taking them.
The risk of birth defects from getting too much vitamin A is the reason that pregnant women and those trying to conceive should stay away from the prescription acne drug isotretinoin (also known by the brand name
Accutane, among others) and other drugs related to retinol (a compound of vitamin A), including topical tretinoin (Retin-A), which is used for skin conditions.
Basically if your vitamins say they are unsuitable for TTC they are likely to contain the wrong sort of Vitamin A, which wont stop you conceiving but may be harmful to the baby once you are BFP... I would give them to your OH and get some more for you
