The CDC and WHO are always (understandably) over-cautious, they don't want to risk an outbreak or be accused of not warning people.
Indeed, as recently as last year there was a Zika case in Buenos Aires. While previously it was contained to the Tucumán province, it doesn't mean it couldn't spread or be transmitted in an airport, for example.
While any first hand info is going to be merely anecdotal, if you're pregnant, you should speak to your clinician/doctor about preventative methods, as they'll have the latest information, or access to it at least, as this is a reasonably quickly changing situation. They may advise against it, or provide you with some preventative measures.
Remember, not getting medical advice, or going against government/medical advice can cause some insurance policies to decline any claims, so best to check with your travel insurance as well as to what they recommend, as opposed to a random first hand knowledge on the internet.
Hope that helps a little.