I've been suffering from this burning labia/itching for a few weeks now. At first I thought it was a yeast infection, but it didn't clear up with a 3-day treatment and it doesn't feel like a yeast infection.
I think I've settled on vulvar variscosities. Basically, varicose veins/hemorrhoids of the vulva. It's worse at the peak of my vulva and along the hair line. Sorry TMI. Worse at the end of the day when I've been chasing my toddler around. It's an intermittent burning.
Witch hazel sprays and pads cut down on the the swelling/burning/itching. When it gets really bad, I apply some vagisil. Sitting with my legs elevated helps.
Check with your health care provider. From what I've read online vulvar varicosities (the Mayo clinic website has a page on it) are common in pregnancy and usually are only managed. It's a combination of weight on the blood vessels and increased blood flow due to pregnancy hormones.