27wks and almost passed out

So last night at work.. I’m an RN who works nights.. I was charting on pts and all of the sudden got really light headed and dizzy it lasted for about a minute.. I thought I was going to pass out.. luckily I was sitting and charting.. don’t know if what would have happened if I had been standing.. but I’ve never had his happen before and last this long... a girl I work with says it’s normal during pregnancy.. was this something that is normal?? My blood pressure was fine and so was my blood sugar..