Pure Acetone is not a harmful substance. It’s very dehydrating and can cause irritation on very dry skin, but it should have no effect on a pregnancy. Only time I’ve seen clients or techs react to removers is if it has added substances like a scent or lubricant. If your client is sceptical you could get pure acetone made safe for skin use from a pharmacy. Don’t know your brand of remover, but highly doubtful it will give any side effects.