Before my first pregnancy, I was on a daily migraine preventative. I had to wean off of it for the pregnancy. (I got all sorts of migraines... barometric pressure trigger, food trigger, dehydration trigger, stress, hormones...) Thankfully, I only got a handful of manageable migraines while pregnant. Then the breastfeeding hormones kept the bad ones away until relatively recently (DD1 is 21 months old). I probably was just getting to the point when I would have considered resuming my meds, except we were going to start TTC. Obviously, I'm here, so still med-free.
It's likely that if your migraines were hormonally-triggered, you may not suffer from them through pregnancy and breastfeeding. However, if you DO experience some, try keeping a food/sleep/stress log and see if you can make any correlations.