Unfortunately, the symptoms of migraine often mimic TIA symptoms, which is what's happened in your case. The odds are great that this was migraine because of all the classic visual symptoms, plus the fact that migraine is very common during pregnancy, and it sounds like you've been having optical migraine without the headache. Further stuff which makes it likely to be migraine-related is that the tingling you experienced in one arm eventually spread to the other as well. Strokes or TIAs are always unilateral unless there has been a catastropic bleed on the brain (in which case you wouldn't likely be typing anything or doing much else for quite a while). The clots that are sometimes associated with Factor V Leiden are sometimes the cause of a stroke, more often a pulmonary embolism, but in either case the clots are usually too large to cause repeated TIAs with complete recovery in between. While this condition does place you at some slight risk of a DVT and possible pulmonary embolism (or even, though less likely, a stroke), it really does sound as though you've experienced multiple episodes of optical migraine. You didn't mention any headached developing, but you did mention the sense of having looked at a bright light, which is also classic for optical migraine. If you don't get the headaches you are ahead of the game, although the aura symptoms you've described can be pretty disturbing, at least until they've happened a few times. If you do happen to get the headaches, I'm going to assume they develop during or after these more bizarre symptoms, and that would also argue in favor of migraine, since TIAs or any sort of cerebral embolism almost never causes headache (although cerebral hemmorhage, which is not a feature of eboli, causes exquisite pain as a rule). Based on all this, it seems extremely likely your problems have been due to optical migraine aggravated by pregnancy.
I hope this is helpful. Best of luck to you and please follow up here as needed.
John Kenyon, EMT, CCT
Non-invasive cardiology tech, Emergency and Critical Care technician, Critical Incident Stress Mgmt. specialist