with all 3 of my prg i have experienced dizzy spells and light headedness.

with my first i was around 17wks prg and standing in a queue at the bank it was a saturday morning and really busy, i passed out the next thing someone was helping me onto a chair and getting me a drink of water and asking if anyone had a phone to call an ambulance - omg i was so embarressed had to explain that it was cause i was prg (i wasn't really showing then) i tell you tho it was a quick way to queue jump lol. i went to my ob two days later and he assured me all was okay - it more than likey was my blood pressure - i tend to have low blood pressure and my iron levels are very low (even when not prg).

i have also heard or read (maybe on here i think) that it called be a symptom of dehydration so make sure you keep drinking heaps of water.

good luck