Congrats!!!! I am so excited for you!
I do not know 100% for certain if it is safe or not but my Dr allowed me to drink it- so I would assume so. I drank 1 bottle of Diet Mountain Dew a day until I switched to Diet Coke, and about 3 or 4 bottles of water with the Crystal Light To Go packets in it. I also do not care for water- plain anyhow!
Toward the end of my pregnancy I decided to drink more water with less in it because of the heat and all. I started putting oranges and lemons in it which was great tasting- if it was cold enough.
The biggest thing my Dr kept telling me is that if it is done in moderation it is fine!
Good luck to you and many blessings!