I don't know if they are an indicator, but when I first read your thread title, I thought you were going to ask about what happens if you get a migraine during labour, which is what I've been stressing about lately. I'd love to know how your sister goes during labour and if her migraine is still a problem or not.

I get hormonal migraines, which got really really bad in first trimester, but have slacked off now thank goodness. I've actually got in my birth plan that I want pain relief if I get a migraine during labour, but not for labour itself IYKWIM. Unfortunately, aspirin usually does the trick for me, but I'm assuming I couldn't have that during labour due to the risk of bleeding.